The R13B03 release.OTP_R13B03

12 files changed, 18411 insertions, 0 deletions

diff --git a/lib/syntax_tools/src/Makefile b/lib/syntax_tools/src/Makefile
new file mode 100644
index 0000000000..5ffe85c975
--- /dev/null
+++ b/lib/syntax_tools/src/Makefile
@@ -0,0 +1,84 @@
+#
+# Copyright (C) 2004, Ericsson Telecommunications
+# Authors: Richard Carlsson, Bertil Karlsson
+#
+include $(ERL_TOP)/make/target.mk
+include $(ERL_TOP)/make/$(TARGET)/otp.mk
+
+# ----------------------------------------------------
+# Application version
+# ----------------------------------------------------
+include ../vsn.mk
+VSN=$(SYNTAX_TOOLS_VSN)
+
+# ----------------------------------------------------
+# Release directory specification
+# ----------------------------------------------------
+RELSYSDIR = $(RELEASE_PATH)/lib/syntax_tools-$(VSN)
+
+
+#
+# Common Macros
+#
+
+EBIN = ../ebin
+
+ERL_COMPILE_FLAGS += +warn_unused_vars +nowarn_shadow_vars +warn_unused_import +warn_obsolete_guard
+
+SOURCES=erl_syntax.erl erl_prettypr.erl erl_syntax_lib.erl	\
+	erl_comment_scan.erl erl_recomment.erl erl_tidy.erl	\
+	epp_dodger.erl prettypr.erl igor.erl
+
+OBJECTS=$(SOURCES:%.erl=$(EBIN)/%.$(EMULATOR)) $(APP_TARGET) $(APPUP_TARGET)
+
+APP_FILE= syntax_tools.app
+APP_SRC= $(APP_FILE).src
+APP_TARGET= $(EBIN)/$(APP_FILE)
+                                                                                
+APPUP_FILE= syntax_tools.appup
+APPUP_SRC= $(APPUP_FILE).src
+APPUP_TARGET= $(EBIN)/$(APPUP_FILE)
+                                                                                
+# ----------------------------------------------------
+# Targets
+# ----------------------------------------------------
+                                                                                
+debug opt: $(OBJECTS)
+
+all: $(OBJECTS)
+
+
+clean:
+	rm -f $(OBJECTS)
+	rm -f core *~
+
+distclean: clean
+
+realclean: clean
+
+$(EBIN)/%.$(EMULATOR):%.erl
+	erlc -W $(ERL_COMPILE_FLAGS) -o$(EBIN) $<
+
+# ----------------------------------------------------
+# Special Build Targets
+# ----------------------------------------------------
+                                                                                
+$(APP_TARGET): $(APP_SRC) ../vsn.mk
+	sed -e 's;%VSN%;$(VSN);' $< > $@
+                                                                                
+$(APPUP_TARGET): $(APPUP_SRC) ../vsn.mk
+	sed -e 's;%VSN%;$(VSN);' $< > $@
+
+# ----------------------------------------------------
+# Release Target
+# ----------------------------------------------------
+include $(ERL_TOP)/make/otp_release_targets.mk
+
+release_spec: opt
+	$(INSTALL_DIR) $(RELSYSDIR)/ebin
+	$(INSTALL_DATA) $(OBJECTS) $(RELSYSDIR)/ebin
+	$(INSTALL_DIR) $(RELSYSDIR)/src
+	$(INSTALL_DATA) $(SOURCES) $(RELSYSDIR)/src
+
+release_docs_spec:
+
diff --git a/lib/syntax_tools/src/epp_dodger.erl b/lib/syntax_tools/src/epp_dodger.erl
new file mode 100644
index 0000000000..7aef549574
--- /dev/null
+++ b/lib/syntax_tools/src/epp_dodger.erl
@@ -0,0 +1,791 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 2001-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc `epp_dodger' - bypasses the Erlang preprocessor.
+%%
+%% <p>This module tokenises and parses most Erlang source code without
+%% expanding preprocessor directives and macro applications, as long as
+%% these are syntactically "well-behaved". Because the normal parse
+%% trees of the `erl_parse' module cannot represent these things
+%% (normally, they are expanded by the Erlang preprocessor {@link
+%% //stdlib/epp} before the parser sees them), an extended syntax tree
+%% is created, using the {@link erl_syntax} module.</p>
+
+
+%% NOTES:
+%%
+%% * It's OK if the result does not parse - then at least nothing
+%% strange happens, and the user can resort to full preprocessing.
+%% However, we must avoid generating a token stream that is accepted by
+%% the parser, but has a different meaning than the intended. A typical
+%% example is when someone uses token-level string concatenation with
+%% macros, as in `"foo" ?bar' (where `?bar' expands to a string). If we
+%% replace the tokens `? bar' with `( ... )', to preserve precedence,
+%% the result will be parsed as an application `"foo" ( ... )' and cause
+%% trouble later on. We must detect such cases and report an error.
+%% 
+%% * It is pointless to add a mechanism for tracking which macros are
+%% known to take arguments, and which are known to take no arguments,
+%% since a lot of the time we will not have seen the macro definition
+%% anyway (it's usually in a header file). Hence, we try to use
+%% heuristics instead. In most cases, the token sequence `? foo ('
+%% indicates that it is a call of a macro that is supposed to take
+%% arguments, but e.g., in the context `: ? foo (', the argument list
+%% typically belongs to a remote function call, as in `m:?f(...)' and
+%% should be parsed as `m:(?f)(...)' unless it is actually a try-clause
+%% pattern such as `throw:?f(...) ->'.
+%% 
+%% * We do our best to make macros without arguments pass the parsing
+%% stage transparently. Atoms are accepted in most contexts, but
+%% variables are not, so we use only atoms to encode these macros.
+%% Sadly, the parsing sometimes discards even the line number info from
+%% atom tokens, so we can only use the actual characters for this.
+%%
+%% * We recognize `?m(...' at the start of a form and prevent this from
+%% being interpreted as a macro with arguments, since it is probably a
+%% function definition. Likewise with attributes `-?m(...'.
+
+-module(epp_dodger).
+
+-export([parse_file/1, quick_parse_file/1, parse_file/2,
+	 quick_parse_file/2, parse/1, quick_parse/1, parse/2,
+	 quick_parse/2, parse/3, quick_parse/3, parse_form/2,
+	 parse_form/3, quick_parse_form/2, quick_parse_form/3,
+	 format_error/1, tokens_to_string/1]).
+
+
+%% The following should be: 1) pseudo-uniquely identifiable, and 2)
+%% cause nice looking error messages when the parser has to give up.
+
+-define(macro_call, '? <macro> (').
+-define(atom_prefix, "? ").
+-define(var_prefix, "?,").
+-define(pp_form, '?preprocessor declaration?').
+
+
+%% @type errorinfo() = {ErrorLine::integer(),
+%%                      Module::atom(),
+%%                      Descriptor::term()}.
+%% 
+%% This is a so-called Erlang I/O ErrorInfo structure; see the {@link
+%% //stdlib/io} module for details.
+
+
+%% =====================================================================
+%% @spec parse_file(File) -> {ok, Forms} | {error, errorinfo()}
+%%       File = file:filename()
+%%       Forms = [erl_syntax:syntaxTree()]
+%% 
+%% @equiv parse_file(File, [])
+
+parse_file(File) ->
+    parse_file(File, []).
+
+%% @spec parse_file(File, Options) -> {ok, Forms} | {error, errorinfo()}
+%%       File = file:filename()
+%%       Options = [term()]
+%%       Forms = [erl_syntax:syntaxTree()]
+%% 
+%% @doc Reads and parses a file. If successful, `{ok, Forms}'
+%% is returned, where `Forms' is a list of abstract syntax
+%% trees representing the "program forms" of the file (cf.
+%% `erl_syntax:is_form/1'). Otherwise, `{error,
+%% errorinfo()}' is returned, typically if the file could not be
+%% opened. Note that parse errors show up as error markers in the
+%% returned list of forms; they do not cause this function to fail or
+%% return `{error,errorinfo()}'.
+%%
+%% Options:
+%% <dl>
+%%   <dt>{@type {no_fail, boolean()@}}</dt>
+%%   <dd>If `true', this makes `epp_dodger' replace any program forms
+%%   that could not be parsed with nodes of type `text' (see {@link
+%%   erl_syntax:text/1}), representing the raw token sequence of the
+%%   form, instead of reporting a parse error. The default value is
+%%   `false'.</dd>
+%%   <dt>{@type {clever, boolean()@}}</dt>
+%%   <dd>If set to `true', this makes `epp_dodger' try to repair the
+%%   source code as it seems fit, in certain cases where parsing would
+%%   otherwise fail. Currently, it inserts `++'-operators between string
+%%   literals and macros where it looks like concatenation was intended.
+%%   The default value is `false'.</dd>
+%% </dl>
+%%
+%% @see parse/2
+%% @see quick_parse_file/1
+%% @see erl_syntax:is_form/1
+
+parse_file(File, Options) ->
+    parse_file(File, fun parse/3, Options).
+
+%% @spec quick_parse_file(File) -> {ok, Forms} | {error, errorinfo()}
+%%       File = file:filename()
+%%       Forms = [erl_syntax:syntaxTree()]
+%%
+%% @equiv quick_parse_file(File, [])
+
+quick_parse_file(File) ->
+    quick_parse_file(File, []).
+
+%% @spec quick_parse_file(File, Options) ->
+%%           {ok, Forms} | {error, errorinfo()}
+%%       File = file:filename()
+%%       Options = [term()]
+%%       Forms = [erl_syntax:syntaxTree()]
+%%
+%% @doc Similar to {@link parse_file/2}, but does a more quick-and-dirty
+%% processing of the code. Macro definitions and other preprocessor
+%% directives are discarded, and all macro calls are replaced with
+%% atoms. This is useful when only the main structure of the code is of
+%% interest, and not the details. Furthermore, the quick-parse method
+%% can usually handle more strange cases than the normal, more exact
+%% parsing.
+%%
+%% Options: see {@link parse_file/2}. Note however that for
+%% `quick_parse_file/2', the option `no_fail' is `true' by default.
+%%
+%% @see quick_parse/2
+%% @see parse_file/2
+
+quick_parse_file(File, Options) ->
+    parse_file(File, fun quick_parse/3, Options ++ [no_fail]).
+
+parse_file(File, Parser, Options) ->
+    case file:open(File, [read]) of
+        {ok, Dev} ->
+            try Parser(Dev, 1, Options)
+            after ok = file:close(Dev)
+	    end;
+        {error, _} = Error ->
+            Error
+    end.
+
+
+%% =====================================================================
+%% @spec parse(IODevice) -> {ok, Forms} | {error, errorinfo()}
+%% @equiv parse(IODevice, 1)
+
+parse(Dev) ->
+    parse(Dev, 1).
+
+%% @spec parse(IODevice, StartLine) -> {ok, Forms} | {error, errorinfo()}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Forms = [erl_syntax:syntaxTree()]
+%%
+%% @equiv parse(IODevice, StartLine, [])
+%% @see parse/1
+
+parse(Dev, L) ->
+    parse(Dev, L, []).
+
+%% @spec parse(IODevice, StartLine, Options) ->
+%%           {ok, Forms} | {error, errorinfo()}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Options = [term()]
+%%       Forms = [erl_syntax:syntaxTree()]
+%%
+%% @doc Reads and parses program text from an I/O stream. Characters are
+%% read from `IODevice' until end-of-file; apart from this, the
+%% behaviour is the same as for {@link parse_file/2}. `StartLine' is the
+%% initial line number, which should be a positive integer.
+%%
+%% @see parse/2
+%% @see parse_file/2
+%% @see parse_form/2
+%% @see quick_parse/3
+
+parse(Dev, L0, Options) ->
+    parse(Dev, L0, fun parse_form/3, Options).
+
+%% @spec quick_parse(IODevice) -> {ok, Forms} | {error, errorinfo()}
+%% @equiv quick_parse(IODevice, 1)
+
+quick_parse(Dev) ->
+    quick_parse(Dev, 1).
+
+%% @spec quick_parse(IODevice, StartLine) ->
+%%           {ok, Forms} | {error, errorinfo()}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Forms = [erl_syntax:syntaxTree()]
+%%
+%% @equiv quick_parse(IODevice, StartLine, [])
+%% @see quick_parse/1
+
+quick_parse(Dev, L) ->
+    quick_parse(Dev, L, []).
+
+%% @spec (IODevice, StartLine, Options) ->
+%%           {ok, Forms} | {error, errorinfo()}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Options = [term()]
+%%       Forms = [erl_syntax:syntaxTree()]
+%% 
+%% @doc Similar to {@link parse/3}, but does a more quick-and-dirty
+%% processing of the code. See {@link quick_parse_file/2} for details.
+%%
+%% @see quick_parse/2
+%% @see quick_parse_file/2
+%% @see quick_parse_form/2
+%% @see parse/3
+
+quick_parse(Dev, L0, Options) ->
+    parse(Dev, L0, fun quick_parse_form/3, Options).
+
+parse(Dev, L0, Parser, Options) ->
+    parse(Dev, L0, [], Parser, Options).
+
+parse(Dev, L0, Fs, Parser, Options) ->
+    case Parser(Dev, L0, Options) of
+        {ok, none, L1} ->
+            parse(Dev, L1, Fs, Parser, Options);
+        {ok, F, L1} ->
+            parse(Dev, L1, [F | Fs], Parser, Options);
+        {error, IoErr, L1} ->
+            parse(Dev, L1, [{error, IoErr} | Fs], Parser, Options);
+        {eof, _L1} ->
+            {ok, lists:reverse(Fs)}
+    end.
+
+
+%% =====================================================================
+%% @spec parse_form(IODevice, StartLine) -> {ok, Form, LineNo}
+%%                                        | {eof, LineNo}
+%%                                        | {error, errorinfo(), LineNo}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Form = erl_syntax:syntaxTree()
+%%       LineNo = integer()
+%%
+%% @equiv parse_form(IODevice, StartLine, [])
+%%
+%% @see quick_parse_form/2
+
+parse_form(Dev, L0) ->
+    parse_form(Dev, L0, []).
+
+%% @spec parse_form(IODevice, StartLine, Options) ->
+%%           {ok, Form, LineNo}
+%%         | {eof, LineNo}
+%%         | {error, errorinfo(), LineNo}
+%% 
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Options = [term()]
+%%       Form = erl_syntax:syntaxTree()
+%%       LineNo = integer()
+%%
+%% @doc Reads and parses a single program form from an I/O stream.
+%% Characters are read from `IODevice' until an end-of-form
+%% marker is found (a period character followed by whitespace), or until
+%% end-of-file; apart from this, the behaviour is similar to that of
+%% `parse/3', except that the return values also contain the
+%% final line number given that `StartLine' is the initial
+%% line number, and that `{eof, LineNo}' may be returned.
+%%
+%% @see parse/3
+%% @see parse_form/2
+%% @see quick_parse_form/3
+
+parse_form(Dev, L0, Options) ->
+    parse_form(Dev, L0, fun normal_parser/2, Options).
+
+%% @spec quick_parse_form(IODevice, StartLine) ->
+%%           {ok, Form, LineNo}
+%%         | {eof, LineNo}
+%%         | {error, errorinfo(), LineNo}
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Form = erl_syntax:syntaxTree() | none
+%%       LineNo = integer()
+%%
+%% @equiv quick_parse_form(IODevice, StartLine, [])
+%%
+%% @see parse_form/2
+
+quick_parse_form(Dev, L0) ->
+    quick_parse_form(Dev, L0, []).
+
+%% @spec quick_parse_form(IODevice, StartLine, Options) ->
+%%           {ok, Form, LineNo}
+%%         | {eof, LineNo}
+%%         | {error, errorinfo(), LineNo}
+%%
+%%       IODevice = pid()
+%%       StartLine = integer()
+%%       Options = [term()]
+%%       Form = erl_syntax:syntaxTree()
+%%       LineNo = integer()
+%%
+%% @doc Similar to {@link parse_form/3}, but does a more quick-and-dirty
+%% processing of the code. See {@link quick_parse_file/2} for details.
+%%
+%% @see parse/3
+%% @see quick_parse_form/2
+%% @see parse_form/3
+
+quick_parse_form(Dev, L0, Options) ->
+    parse_form(Dev, L0, fun quick_parser/2, Options).
+
+-record(opt, {clever = false :: boolean()}).
+
+parse_form(Dev, L0, Parser, Options) ->
+    NoFail = proplists:get_bool(no_fail, Options),
+    Opt = #opt{clever = proplists:get_bool(clever, Options)},
+    case io:scan_erl_form(Dev, "", L0) of
+        {ok, Ts, L1} ->
+            case catch {ok, Parser(Ts, Opt)} of
+                {'EXIT', Term} ->
+                    {error, io_error(L1, {unknown, Term}), L1};
+                {error, Term} ->
+		    IoErr = io_error(L1, Term),
+		    {error, IoErr, L1};
+                {parse_error, _IoErr} when NoFail ->
+		    {ok, erl_syntax:set_pos(
+			   erl_syntax:text(tokens_to_string(Ts)),
+			   start_pos(Ts, L1)),
+		     L1};
+                {parse_error, IoErr} ->
+		    {error, IoErr, L1};
+                {ok, F} ->
+                    {ok, F, L1}
+            end;
+        {error, _IoErr, _L1} = Err -> Err;
+        {eof, _L1} = Eof -> Eof
+    end.
+
+io_error(L, Desc) ->
+    {L, ?MODULE, Desc}.
+
+start_pos([T | _Ts], _L) ->
+    element(2, T);
+start_pos([], L) ->
+    L.
+
+%% Exception-throwing wrapper for the standard Erlang parser stage
+
+parse_tokens(Ts) ->
+    parse_tokens(Ts, fun fix_form/1).
+
+parse_tokens(Ts, Fix) ->
+    case erl_parse:parse_form(Ts) of
+        {ok, Form} ->
+            Form;
+        {error, IoErr} ->
+	    case Fix(Ts) of
+		{form, Form} ->
+		    Form;
+		{retry, Ts1, Fix1} ->
+		    parse_tokens(Ts1, Fix1);
+		error ->
+		    throw({parse_error, IoErr})
+	    end
+    end.
+
+%% ---------------------------------------------------------------------
+%% Quick scanning/parsing - deletes macro definitions and other
+%% preprocessor directives, and replaces all macro calls with atoms.
+
+quick_parser(Ts, _Opt) ->
+    filter_form(parse_tokens(quickscan_form(Ts))).
+
+quickscan_form([{'-', _L}, {atom, La, define} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, undef} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, include} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, include_lib} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, ifdef} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, ifndef} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, else} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', _L}, {atom, La, endif} | _Ts]) ->
+    kill_form(La);
+quickscan_form([{'-', L}, {'?', _}, {Type, _, _}=N | [{'(', _} | _]=Ts])
+  when Type =:= atom; Type =:= var ->
+    %% minus, macro and open parenthesis at start of form - assume that
+    %% the macro takes no arguments; e.g. `-?foo(...).'
+    quickscan_macros_1(N, Ts, [{'-', L}]);
+quickscan_form([{'?', _L}, {Type, _, _}=N | [{'(', _} | _]=Ts])
+  when Type =:= atom; Type =:= var ->
+    %% macro and open parenthesis at start of form - assume that the
+    %% macro takes no arguments (see scan_macros for details)
+    quickscan_macros_1(N, Ts, []);
+quickscan_form(Ts) ->
+    quickscan_macros(Ts).
+
+kill_form(L) ->
+    [{atom, L, ?pp_form}, {'(', L}, {')', L}, {'->', L}, {atom, L, kill},
+     {dot, L}].
+
+quickscan_macros(Ts) ->
+    quickscan_macros(Ts, []).
+
+quickscan_macros([{'?',_}, {Type, _, A} | Ts], [{string, L, S} | As])
+  when Type =:= atom; Type =:= var ->
+    %% macro after a string literal: change to a single string
+    {_, Ts1} = skip_macro_args(Ts),
+    S1 = S ++ quick_macro_string(A),
+    quickscan_macros(Ts1, [{string, L, S1} | As]);
+quickscan_macros([{'?',_}, {Type, _, _}=N | [{'(',_}|_]=Ts],
+		 [{':',_}|_]=As)
+  when Type =:= atom; Type =:= var ->
+    %% macro and open parenthesis after colon - check the token
+    %% following the arguments (see scan_macros for details)
+    Ts1 = case skip_macro_args(Ts) of
+	      {_, [{'->',_} | _] = Ts2} -> Ts2;
+	      {_, [{'when',_} | _] = Ts2} -> Ts2;
+	      _ -> Ts    %% assume macro without arguments
+	  end,
+    quickscan_macros_1(N, Ts1, As);
+quickscan_macros([{'?',_}, {Type, _, _}=N | Ts], As)
+  when Type =:= atom; Type =:= var ->
+    %% macro with or without arguments
+    {_, Ts1} = skip_macro_args(Ts),
+    quickscan_macros_1(N, Ts1, As);
+quickscan_macros([T | Ts], As) ->
+    quickscan_macros(Ts, [T | As]);
+quickscan_macros([], As) ->
+    lists:reverse(As).
+
+%% (after a macro has been found and the arglist skipped, if any)
+quickscan_macros_1({_Type, _, A}, [{string, L, S} | Ts], As) ->
+    %% string literal following macro: change to single string
+    S1 = quick_macro_string(A) ++ S,
+    quickscan_macros(Ts, [{string, L, S1} | As]);
+quickscan_macros_1({_Type, L, A}, Ts, As) ->
+    %% normal case - just replace the macro with an atom
+    quickscan_macros(Ts, [{atom, L, quick_macro_atom(A)} | As]).
+
+quick_macro_atom(A) ->
+    list_to_atom("?" ++ atom_to_list(A)).
+
+quick_macro_string(A) ->
+    "(?" ++ atom_to_list(A) ++ ")".
+
+%% Skipping to the end of a macro call, tracking open/close constructs.
+%% @spec (Tokens) -> {Skipped, Rest}
+
+skip_macro_args([{'(',_}=T | Ts]) ->
+    skip_macro_args(Ts, [')'], [T]);
+skip_macro_args(Ts) ->
+    {[], Ts}.
+
+skip_macro_args([{'(',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, [')' | Es], [T | As]);
+skip_macro_args([{'{',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['}' | Es], [T | As]);
+skip_macro_args([{'[',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, [']' | Es], [T | As]);
+skip_macro_args([{'<<',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['>>' | Es], [T | As]);
+skip_macro_args([{'begin',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{'if',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{'case',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{'receive',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{'try',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{'cond',_}=T | Ts], Es, As) ->
+    skip_macro_args(Ts, ['end' | Es], [T | As]);
+skip_macro_args([{E,_}=T | Ts], [E], As) ->		%final close
+    {lists:reverse([T | As]), Ts};
+skip_macro_args([{E,_}=T | Ts], [E | Es], As) ->	%matching close
+    skip_macro_args(Ts, Es, [T | As]);
+skip_macro_args([T | Ts], Es, As) ->
+    skip_macro_args(Ts, Es, [T | As]);
+skip_macro_args([], _Es, _As) ->
+    throw({error, macro_args}).
+
+filter_form({function, _, ?pp_form, _,
+	     [{clause, _, [], [], [{atom, _, kill}]}]}) ->
+    none;
+filter_form(T) ->
+    T.
+
+
+%% ---------------------------------------------------------------------
+%% Normal parsing - try to preserve all information
+
+normal_parser(Ts, Opt) ->
+    rewrite_form(parse_tokens(scan_form(Ts, Opt))).
+
+scan_form([{'-', _L}, {atom, La, define} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, define} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, undef} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, undef} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, include} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, include} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, include_lib} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, include_lib} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, ifdef} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, ifdef} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, ifndef} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, ifndef} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, else} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, else} | scan_macros(Ts, Opt)];
+scan_form([{'-', _L}, {atom, La, endif} | Ts], Opt) ->
+    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
+     {atom, La, endif} | scan_macros(Ts, Opt)];
+scan_form([{'-', L}, {'?', L1}, {Type, _, _}=N | [{'(', _} | _]=Ts], Opt)
+  when Type =:= atom; Type =:= var ->
+    %% minus, macro and open parenthesis at start of form - assume that
+    %% the macro takes no arguments; e.g. `-?foo(...).'
+    macro(L1, N, Ts, [{'-', L}], Opt);
+scan_form([{'?', L}, {Type, _, _}=N | [{'(', _} | _]=Ts], Opt)
+  when Type =:= atom; Type =:= var ->
+    %% macro and open parenthesis at start of form - assume that the
+    %% macro takes no arguments; probably a function declaration on the
+    %% form `?m(...) -> ...', which will not parse if it is rewritten as
+    %% `(?m(...)) -> ...', so it must be handled as `(?m)(...) -> ...'
+    macro(L, N, Ts, [], Opt);
+scan_form(Ts, Opt) ->
+    scan_macros(Ts, Opt).
+
+scan_macros(Ts, Opt) ->
+    scan_macros(Ts, [], Opt).
+
+scan_macros([{'?', _}=M, {Type, _, _}=N | Ts], [{string, L, _}=S | As],
+ 	    #opt{clever = true}=Opt)
+  when Type =:= atom; Type =:= var ->
+    %% macro after a string literal: be clever and insert ++
+    scan_macros([M, N | Ts], [{'++', L}, S | As], Opt);
+scan_macros([{'?', L}, {Type, _, _}=N | [{'(',_}|_]=Ts],
+	    [{':',_}|_]=As, Opt)
+  when Type =:= atom; Type =:= var ->
+    %% macro and open parentheses after colon - probably a call
+    %% `m:?F(...)' so the argument list might belong to the call, not
+    %% the macro - but it could also be a try-clause pattern
+    %% `...:?T(...) ->' - we need to check the token following the
+    %% arguments to decide
+    {Args, Rest} = skip_macro_args(Ts),
+    case Rest of
+	[{'->',_} | _] ->
+	    macro_call(Args, L, N, Rest, As, Opt);
+	[{'when',_} | _] ->
+	    macro_call(Args, L, N, Rest, As, Opt);
+	_ ->
+	    macro(L, N, Ts, As, Opt)
+    end;
+scan_macros([{'?', L}, {Type, _, _}=N | [{'(',_}|_]=Ts], As, Opt)
+  when Type =:= atom; Type =:= var ->
+    %% macro with arguments
+    {Args, Rest} = skip_macro_args(Ts),
+    macro_call(Args, L, N, Rest, As, Opt);
+scan_macros([{'?', L }, {Type, _, _}=N | Ts], As, Opt)
+  when Type =:= atom; Type =:= var ->
+    %% macro without arguments
+    macro(L, N, Ts, As, Opt);
+scan_macros([T | Ts], As, Opt) ->
+    scan_macros(Ts, [T | As], Opt);
+scan_macros([], As, _Opt) ->
+    lists:reverse(As).
+
+%% Rewriting to a call which will be recognized by the post-parse pass
+%% (we insert parentheses to preserve the precedences when parsing).
+
+macro(L, {Type, _, A}, Rest, As, Opt) ->
+    scan_macros_1([], Rest, [{atom,L,macro_atom(Type,A)} | As], Opt).
+
+macro_call([{'(',_}, {')',_}], L, {_, Ln, _}=N, Rest, As, Opt) ->
+    {Open, Close} = parentheses(As),
+    scan_macros_1([], Rest,
+		  lists:reverse(Open ++ [{atom,L,?macro_call},
+					 {'(',L}, N, {')',Ln}] ++ Close,
+				As), Opt);
+macro_call([{'(',_} | Args], L, {_, Ln, _}=N, Rest, As, Opt) ->
+    {Open, Close} = parentheses(As),
+    %% note that we must scan the argument list; it may not be skipped
+    scan_macros_1(Args ++ Close,
+		  Rest,
+		  lists:reverse(Open ++ [{atom,L,?macro_call},
+					 {'(',L}, N, {',',Ln}],
+				As), Opt).
+
+macro_atom(atom, A) ->
+    list_to_atom(?atom_prefix ++ atom_to_list(A));
+macro_atom(var, A) ->
+    list_to_atom(?var_prefix ++ atom_to_list(A)).
+
+%% don't insert parentheses after a string token, to avoid turning
+%% `"string" ?macro' into a "function application" `"string"(...)'
+%% (see note at top of file)
+parentheses([{string, _, _} | _]) ->
+    {[], []};
+parentheses(_) ->
+    {[{'(',0}], [{')',0}]}.
+
+%% (after a macro has been found and the arglist skipped, if any)
+scan_macros_1(Args, [{string, L, _} | _]=Rest, As,
+	      #opt{clever = true}=Opt) ->
+    %% string literal following macro: be clever and insert ++
+    scan_macros(Args ++ [{'++', L} | Rest],  As, Opt);
+scan_macros_1(Args, Rest, As, Opt) ->
+    %% normal case - continue scanning
+    scan_macros(Args ++ Rest, As, Opt).
+
+rewrite_form({function, L, ?pp_form, _,
+              [{clause, _, [], [], [{call, _, A, As}]}]}) ->
+    erl_syntax:set_pos(erl_syntax:attribute(A, rewrite_list(As)), L);
+rewrite_form({function, L, ?pp_form, _, [{clause, _, [], [], [A]}]}) ->
+    erl_syntax:set_pos(erl_syntax:attribute(A), L);
+rewrite_form(T) ->
+    rewrite(T).
+
+rewrite_list([T | Ts]) ->
+    [rewrite(T) | rewrite_list(Ts)];
+rewrite_list([]) ->
+    [].
+
+%% Note: as soon as we start using erl_syntax:subtrees/1 and similar
+%% functions, we cannot assume that we know the exact representation of
+%% the syntax tree anymore - we must use erl_syntax functions to analyze
+%% and decompose the data.
+
+rewrite(Node) ->
+    case erl_syntax:type(Node) of
+	atom ->
+	    case atom_to_list(erl_syntax:atom_value(Node)) of
+		?atom_prefix ++ As ->
+		    A1 = list_to_atom(As),
+		    N = erl_syntax:copy_pos(Node, erl_syntax:atom(A1)),
+		    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
+		?var_prefix ++ As ->
+		    A1 = list_to_atom(As),
+		    N = erl_syntax:copy_pos(Node, erl_syntax:variable(A1)),
+		    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
+		_ ->
+		    Node
+	    end;
+	application ->
+	    F = erl_syntax:application_operator(Node),
+	    case erl_syntax:type(F) of
+		atom ->
+		    case erl_syntax:atom_value(F) of
+			?macro_call ->
+			    [A | As] = erl_syntax:application_arguments(Node),
+			    M = erl_syntax:macro(A, rewrite_list(As)),
+			    erl_syntax:copy_pos(Node, M);
+			_ ->
+			    rewrite_1(Node)
+		    end;
+		_ ->
+		    rewrite_1(Node)
+	    end;
+	_ ->
+	    rewrite_1(Node)
+    end.
+
+rewrite_1(Node) ->
+    case erl_syntax:subtrees(Node) of
+	[] ->
+	    Node;
+	Gs ->
+	    Node1 = erl_syntax:make_tree(erl_syntax:type(Node),
+					 [[rewrite(T) || T <- Ts]
+					  || Ts <- Gs]),
+	    erl_syntax:copy_pos(Node, Node1)
+    end.
+
+%% attempting a rescue operation on a token sequence for a single form
+%% if it could not be parsed after the normal treatment
+
+fix_form([{atom, _, ?pp_form}, {'(', _}, {')', _}, {'->', _},
+	  {atom, _, define}, {'(', _} | _]=Ts) ->
+    case lists:reverse(Ts) of
+	[{dot, _}, {')', _} | _] ->
+	    {retry, Ts, fun fix_define/1};
+	[{dot, L} | Ts1] ->
+	    Ts2 = lists:reverse([{dot, L}, {')', L} | Ts1]),
+	    {retry, Ts2, fun fix_define/1};
+	_ ->
+	    error
+    end;
+fix_form(_Ts) ->
+    error.
+
+fix_define([{atom, L, ?pp_form}, {'(', _}, {')', _}, {'->', _},
+	    {atom, La, define}, {'(', _}, N, {',', _} | Ts]) ->
+    [{dot, _}, {')', _} | Ts1] = lists:reverse(Ts),
+    S = tokens_to_string(lists:reverse(Ts1)),
+    A = erl_syntax:set_pos(erl_syntax:atom(define), La),
+    Txt = erl_syntax:set_pos(erl_syntax:text(S), La),
+    {form, erl_syntax:set_pos(erl_syntax:attribute(A, [N, Txt]), L)};
+fix_define(_Ts) ->
+    error.
+
+%% @spec (Tokens::[term()]) -> string()
+%% 
+%% @doc Generates a string corresponding to the given token sequence.
+%% The string can be re-tokenized to yield the same token list again.
+
+tokens_to_string([{atom,_,A} | Ts]) ->
+    io_lib:write_atom(A) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([{string, _, S} | Ts]) ->
+    io_lib:write_string(S) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([{float, _, F} | Ts]) ->
+    float_to_list(F) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([{integer, _, N} | Ts]) ->
+    integer_to_list(N) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([{var,_,A} | Ts]) ->
+    atom_to_list(A) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([{dot,_} | Ts]) ->
+    ".\n" ++ tokens_to_string(Ts);
+tokens_to_string([{A,_} | Ts]) ->
+    atom_to_list(A) ++ " " ++ tokens_to_string(Ts);
+tokens_to_string([]) ->
+    "".
+
+
+%% @spec (Descriptor::term()) -> string()
+%% @hidden
+%% @doc Callback function for formatting error descriptors. Not for
+%% normal use.
+
+format_error(macro_args) ->
+    errormsg("macro call missing end parenthesis");
+format_error({unknown, Reason}) ->
+    errormsg(io_lib:format("unknown error: ~P", [Reason, 15])).
+
+errormsg(String) ->
+    io_lib:format("~s: ~s", [?MODULE, String]).
+
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/erl_comment_scan.erl b/lib/syntax_tools/src/erl_comment_scan.erl
new file mode 100644
index 0000000000..df1449da4e
--- /dev/null
+++ b/lib/syntax_tools/src/erl_comment_scan.erl
@@ -0,0 +1,280 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1997-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Functions for reading comment lines from Erlang source code.
+
+-module(erl_comment_scan).
+
+-export([file/1, join_lines/1, scan_lines/1, string/1]).
+
+
+%% =====================================================================
+%% @spec file(FileName::file:filename()) -> [Comment]
+%%
+%%	    Comment = {Line, Column, Indentation, Text}
+%%	    Line = integer()
+%%          Column = integer()
+%%          Indentation = integer()
+%%          Text = [string()]
+%%
+%% @doc Extracts comments from an Erlang source code file. Returns a
+%% list of entries representing <em>multi-line</em> comments, listed in
+%% order of increasing line-numbers. For each entry, `Text'
+%% is a list of strings representing the consecutive comment lines in
+%% top-down order; the strings contain <em>all</em> characters following
+%% (but not including) the first comment-introducing `%'
+%% character on the line, up to (but not including) the line-terminating
+%% newline.
+%%
+%% Furthermore, `Line' is the line number and
+%% `Column' the left column of the comment (i.e., the column
+%% of the comment-introducing `%' character).
+%% `Indent' is the indentation (or padding), measured in
+%% character positions between the last non-whitespace character before
+%% the comment (or the left margin), and the left column of the comment.
+%% `Line' and `Column' are always positive
+%% integers, and `Indentation' is a nonnegative integer.
+%%
+%% Evaluation exits with reason `{read, Reason}' if a read
+%% error occurred, where `Reason' is an atom corresponding to
+%% a Posix error code; see the module {@link //kernel/file} for details.
+
+file(Name) ->
+    Name1 = filename(Name),
+    case catch {ok, file:read_file(Name1)} of
+	{ok, V} ->
+	    case V of
+		{ok, B} ->
+		    string(binary_to_list(B));
+		{error, E} ->
+		    error_read_file(Name1),
+		    exit({read, E})
+	    end;
+	{'EXIT', E} ->
+	    error_read_file(Name1),
+	    exit(E);
+	R ->
+	    error_read_file(Name1),
+	    throw(R)
+    end.
+
+
+%% =====================================================================
+%% string(string()) -> [Comment]
+%%
+%%	    Comment = {Line, Column, Indentation, Text}
+%%	    Line = integer()
+%%          Column = integer()
+%%          Indentation = integer()
+%%          Text = [string()]
+%%
+%% @doc Extracts comments from a string containing Erlang source code.
+%% Except for reading directly from a string, the behaviour is the same
+%% as for {@link file/1}.
+%%
+%% @see file/1
+
+string(Text) ->
+    lists:reverse(join_lines(scan_lines(Text))).
+
+
+%% =====================================================================
+%% @spec scan_lines(string()) -> [CommentLine]
+%%
+%%	    CommentLine = {Line, Column, Indent, Text}
+%%	    Line = integer()
+%%	    Column = integer()
+%%	    Indent = integer()
+%%	    Text = string()
+%%
+%% @doc Extracts individual comment lines from a source code string.
+%% Returns a list of comment lines found in the text, listed in order of
+%% <em>decreasing</em> line-numbers, i.e., the last comment line in the
+%% input is first in the resulting list. `Text' is a single
+%% string, containing all characters following (but not including) the
+%% first comment-introducing `%' character on the line, up
+%% to (but not including) the line-terminating newline. For details on
+%% `Line', `Column' and `Indent', see {@link file/1}.
+
+scan_lines(Text) ->
+    scan_lines(Text, 1, 0, 0, []).
+
+scan_lines([$\040 | Cs], L, Col, M, Ack) ->
+    scan_lines(Cs, L, Col + 1, M, Ack);
+scan_lines([$\t | Cs], L, Col, M, Ack) ->
+    scan_lines(Cs, L, tab(Col), M, Ack);
+scan_lines([$\n | Cs], L, _Col, _M, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);
+scan_lines([$\r, $\n | Cs], L, _Col, _M, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);
+scan_lines([$\r | Cs], L, _Col, _M, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);
+scan_lines([$% | Cs], L, Col, M, Ack) ->
+    scan_comment(Cs, "", L, Col, M, Ack);
+scan_lines([$$ | Cs], L, Col, _M, Ack) ->
+    scan_char(Cs, L, Col + 1, Ack);
+scan_lines([$" | Cs], L, Col, _M, Ack) ->
+    scan_string(Cs, $", L, Col + 1, Ack);
+scan_lines([$' | Cs], L, Col, _M, Ack) ->
+    scan_string(Cs, $', L, Col + 1, Ack);
+scan_lines([_C | Cs], L, Col, _M, Ack) ->
+    N = Col + 1,
+    scan_lines(Cs, L, N, N, Ack);
+scan_lines([], _L, _Col, _M, Ack) ->
+    Ack.
+
+tab(Col) ->
+    Col - (Col rem 8) + 8.
+
+scan_comment([$\n | Cs], Cs1, L, Col, M, Ack) ->
+    seen_comment(Cs, Cs1, L, Col, M, Ack);
+scan_comment([$\r, $\n | Cs], Cs1, L, Col, M, Ack) ->
+    seen_comment(Cs, Cs1, L, Col, M, Ack);
+scan_comment([$\r | Cs], Cs1, L, Col, M, Ack) ->
+    seen_comment(Cs, Cs1, L, Col, M, Ack);
+scan_comment([C | Cs], Cs1, L, Col, M, Ack) ->
+    scan_comment(Cs, [C | Cs1], L, Col, M, Ack);
+scan_comment([], Cs1, L, Col, M, Ack) ->
+    seen_comment([], Cs1, L, Col, M, Ack).
+
+%% Add a comment line to the ackumulator and return to normal
+%% scanning. Note that we compute column positions starting at 0
+%% internally, but the column values in the comment descriptors
+%% should start at 1.
+
+seen_comment(Cs, Cs1, L, Col, M, Ack) ->
+    %% Compute indentation and strip trailing spaces
+    N = Col - M,
+    Text = lists:reverse(string:strip(Cs1, left)),
+    Ack1 = [{L, Col + 1, N, Text} | Ack],
+    scan_lines(Cs, L + 1, 0, 0, Ack1).
+
+scan_string([Quote | Cs], Quote, L, Col, Ack) ->
+    N = Col + 1,
+    scan_lines(Cs, L, N, N, Ack);
+scan_string([$\t | Cs], Quote, L, Col, Ack) ->
+    scan_string(Cs, Quote, L, tab(Col), Ack);
+scan_string([$\n | Cs], Quote, L, _Col, Ack) ->
+    %% Newlines should really not occur in strings/atoms, but we
+    %% want to be well behaved even if the input is not.
+    scan_string(Cs, Quote, L + 1, 0, Ack);
+scan_string([$\r, $\n | Cs], Quote, L, _Col, Ack) ->
+    scan_string(Cs, Quote, L + 1, 0, Ack);
+scan_string([$\r | Cs], Quote, L, _Col, Ack) ->
+    scan_string(Cs, Quote, L + 1, 0, Ack);
+scan_string([$\\, _C | Cs], Quote, L, Col, Ack) ->
+    scan_string(Cs, Quote, L, Col + 2, Ack);  % ignore character C
+scan_string([_C | Cs], Quote, L, Col, Ack) ->
+    scan_string(Cs, Quote, L, Col + 1, Ack);
+scan_string([], _Quote, _L, _Col, Ack) ->
+    %% Finish quietly.
+    Ack.
+
+scan_char([$\t | Cs], L, Col, Ack) ->
+    N = tab(Col),
+    scan_lines(Cs, L, N, N, Ack);    % this is not just any whitespace
+scan_char([$\n | Cs], L, _Col, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);    % handle this, just in case
+scan_char([$\r, $\n | Cs], L, _Col, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);
+scan_char([$\r | Cs], L, _Col, Ack) ->
+    scan_lines(Cs, L + 1, 0, 0, Ack);
+scan_char([$\\, _C | Cs], L, Col, Ack) ->
+    N = Col + 2,    % character C must be ignored
+    scan_lines(Cs, L, N, N, Ack);
+scan_char([_C | Cs], L, Col, Ack) ->
+    N = Col + 1,    % character C must be ignored
+    scan_lines(Cs, L, N, N, Ack);
+scan_char([], _L, _Col, Ack) ->
+    %% Finish quietly.
+    Ack.
+
+
+%% =====================================================================
+%% @spec join_lines([CommentLine]) -> [Comment]
+%%
+%%	    CommentLine = {Line, Column, Indent, string()}
+%%	    Line = integer()
+%%	    Column = integer()
+%%	    Indent = integer()
+%%	    Comment = {Line, Column, Indent, Text}
+%%	    Text = [string()]
+%%
+%% @doc Joins individual comment lines into multi-line comments. The
+%% input is a list of entries representing individual comment lines,
+%% <em>in order of decreasing line-numbers</em>; see
+%% {@link scan_lines/1} for details. The result is a list of
+%% entries representing <em>multi-line</em> comments, <em>still listed
+%% in order of decreasing line-numbers</em>, but where for each entry,
+%% `Text' is a list of consecutive comment lines in order of
+%% <em>increasing</em> line-numbers (i.e., top-down).
+%%
+%% @see scan_lines/1
+
+join_lines([{L, Col, Ind, Txt} | Lines]) ->
+    join_lines(Lines, [Txt], L, Col, Ind);
+join_lines([]) ->
+    [].
+
+%% In the following, we assume that the current `Txt' is never empty.
+%% Recall that the list is in reverse line-number order.
+
+join_lines([{L1, Col1, Ind1, Txt1} | Lines], Txt, L, Col, Ind) ->
+    if L1 =:= L - 1, Col1 =:= Col, Ind + 1 =:= Col ->
+	    %% The last test above checks that the previous
+	    %% comment was alone on its line; otherwise it won't
+	    %% be joined with the current; this is not always what
+	    %% one wants, but works well in general.
+	    join_lines(Lines, [Txt1 | Txt], L1, Col1, Ind1);
+       true ->
+	    %% Finish the current comment and let the new line
+	    %% start the next one.
+	    [{L, Col, Ind, Txt}
+	     | join_lines(Lines, [Txt1], L1, Col1, Ind1)]
+    end;
+join_lines([], Txt, L, Col, Ind) ->
+    [{L, Col, Ind, Txt}].
+
+
+%% =====================================================================
+%% Utility functions for internal use
+
+filename([C|T]) when is_integer(C), C > 0, C =< 255 ->
+    [C | filename(T)];
+filename([H|T]) ->
+    filename(H) ++ filename(T);
+filename([]) ->
+    [];
+filename(N) when is_atom(N) ->
+    atom_to_list(N);
+filename(N) ->
+    report_error("bad filename: `~P'.", [N, 25]),
+    exit(error).
+
+error_read_file(Name) ->
+    report_error("error reading file `~s'.", [Name]).
+
+report_error(S, Vs) ->
+    error_logger:error_msg(lists:concat([?MODULE, ": ", S, "\n"]), Vs).
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/erl_prettypr.erl b/lib/syntax_tools/src/erl_prettypr.erl
new file mode 100644
index 0000000000..8d2f4facea
--- /dev/null
+++ b/lib/syntax_tools/src/erl_prettypr.erl
@@ -0,0 +1,1153 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1997-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Pretty printing of abstract Erlang syntax trees.
+%%
+%% This module is a front end to the pretty-printing library module
+%% `prettypr', for text formatting of abstract syntax trees defined by
+%% the module `erl_syntax'.
+
+-module(erl_prettypr).
+
+-export([format/1, format/2, best/1, best/2, layout/1, layout/2,
+	 get_ctxt_precedence/1, set_ctxt_precedence/2,
+	 get_ctxt_paperwidth/1, set_ctxt_paperwidth/2,
+	 get_ctxt_linewidth/1, set_ctxt_linewidth/2, get_ctxt_hook/1,
+	 set_ctxt_hook/2, get_ctxt_user/1, set_ctxt_user/2]).
+
+-import(prettypr, [text/1, nest/2, above/2, beside/2, sep/1, par/1,
+		   par/2, floating/3, floating/1, break/1, follow/2,
+		   follow/3, empty/0]).
+
+-import(erl_parse, [preop_prec/1, inop_prec/1, func_prec/0,
+		    max_prec/0]).
+
+-define(PADDING, 2).
+-define(PAPER, 80).
+-define(RIBBON, 56).
+-define(NOUSER, undefined).
+-define(NOHOOK, none).
+
+-record(ctxt, {prec = 0,
+	       sub_indent = 2,
+	       break_indent = 4,
+	       clause = undefined,
+	       hook = ?NOHOOK,
+	       paper = ?PAPER,
+	       ribbon = ?RIBBON,
+	       user = ?NOUSER}).
+
+
+%% =====================================================================
+%% The following functions examine and modify contexts:
+
+%% @spec (context()) -> context()
+%% @doc Returns the operator precedence field of the prettyprinter
+%% context.
+%%
+%% @see set_ctxt_precedence/2
+
+get_ctxt_precedence(Ctxt) ->
+    Ctxt#ctxt.prec.
+
+%% @spec (context(), integer()) -> context()
+%%
+%% @doc Updates the operator precedence field of the prettyprinter
+%% context. See the {@link //stdlib/erl_parse} module for operator precedences.
+%%
+%% @see //stdlib/erl_parse
+%% @see get_ctxt_precedence/1
+
+set_ctxt_precedence(Ctxt, Prec) ->
+    set_prec(Ctxt, Prec).
+
+set_prec(Ctxt, Prec) ->
+    Ctxt#ctxt{prec = Prec}.    % used internally
+
+reset_prec(Ctxt) ->
+    set_prec(Ctxt, 0).    % used internally
+
+%% @spec (context()) -> integer()
+%% @doc Returns the paper widh field of the prettyprinter context.
+%% @see set_ctxt_paperwidth/2
+
+get_ctxt_paperwidth(Ctxt) ->
+    Ctxt#ctxt.paper.
+
+%% @spec (context(), integer()) -> context()
+%%
+%% @doc Updates the paper widh field of the prettyprinter context.
+%%
+%% Note: changing this value (and passing the resulting context to a
+%% continuation function) does not affect the normal formatting, but may
+%% affect user-defined behaviour in hook functions.
+%%
+%% @see get_ctxt_paperwidth/1
+
+set_ctxt_paperwidth(Ctxt, W) ->
+    Ctxt#ctxt{paper = W}.
+
+%% @spec (context()) -> integer()
+%% @doc Returns the line widh field of the prettyprinter context.
+%% @see set_ctxt_linewidth/2
+
+get_ctxt_linewidth(Ctxt) ->
+    Ctxt#ctxt.ribbon.
+
+%% @spec (context(), integer()) -> context()
+%%
+%% @doc Updates the line widh field of the prettyprinter context.
+%%
+%% Note: changing this value (and passing the resulting context to a
+%% continuation function) does not affect the normal formatting, but may
+%% affect user-defined behaviour in hook functions.
+%%
+%% @see get_ctxt_linewidth/1
+
+set_ctxt_linewidth(Ctxt, W) ->
+    Ctxt#ctxt{ribbon = W}.
+
+%% @spec (context()) -> hook()
+%% @doc Returns the hook function field of the prettyprinter context.
+%% @see set_ctxt_hook/2
+
+get_ctxt_hook(Ctxt) ->
+    Ctxt#ctxt.hook.
+
+%% @spec (context(), hook()) -> context()
+%% @doc Updates the hook function field of the prettyprinter context.
+%% @see get_ctxt_hook/1
+
+set_ctxt_hook(Ctxt, Hook) ->
+    Ctxt#ctxt{hook = Hook}.
+
+%% @spec (context()) -> term()
+%% @doc Returns the user data field of the prettyprinter context.
+%% @see set_ctxt_user/2
+
+get_ctxt_user(Ctxt) ->
+    Ctxt#ctxt.user.
+
+%% @spec (context(), term()) -> context()
+%% @doc Updates the user data field of the prettyprinter context.
+%% @see get_ctxt_user/1
+
+set_ctxt_user(Ctxt, X) ->
+    Ctxt#ctxt{user = X}.
+
+
+%% =====================================================================
+%% @spec format(Tree::syntaxTree()) -> string()
+%% @equiv format(Tree, [])
+
+format(Node) ->
+    format(Node, []).
+
+
+%% =====================================================================
+%% @spec format(Tree::syntaxTree(), Options::[term()]) -> string()
+%%           syntaxTree() = erl_syntax:syntaxTree()
+%%
+%% @type hook() = (syntaxTree(), context(), Continuation) -> document()
+%%	    Continuation = (syntaxTree(), context()) -> document().
+%%
+%% A call-back function for user-controlled formatting. See {@link
+%% format/2}.
+%%
+%% @type context(). A representation of the current context of the
+%% pretty-printer. Can be accessed in hook functions.
+%%
+%% @doc Prettyprint-formats an abstract Erlang syntax tree as text. For
+%% example, if you have a `.beam' file that has been compiled with
+%% `debug_info', the following should print the source code for the
+%% module (as it looks in the debug info representation):
+%% ```{ok,{_,[{abstract_code,{_,AC}}]}} =
+%%            beam_lib:chunks("myfile.beam",[abstract_code]),
+%%    io:put_chars(erl_prettypr:format(erl_syntax:form_list(AC)))
+%% '''
+%%
+%% Available options:
+%% <dl>
+%%   <dt>{hook, none | {@link hook()}}</dt>
+%%       <dd>Unless the value is `none', the given function is called
+%%       for each node whose list of annotations is not empty; see below
+%%       for details. The default value is `none'.</dd>
+%%
+%%   <dt>{paper, integer()}</dt>
+%%       <dd>Specifies the preferred maximum number of characters on any
+%%       line, including indentation. The default value is 80.</dd>
+%%
+%%   <dt>{ribbon, integer()}</dt>
+%%       <dd>Specifies the preferred maximum number of characters on any
+%%       line, not counting indentation. The default value is 65.</dd>
+%%
+%%   <dt>{user, term()}</dt>
+%%       <dd>User-specific data for use in hook functions. The default
+%%       value is `undefined'.</dd>
+%% </dl>
+%%
+%% A hook function (cf. the {@link hook()} type) is passed the current
+%% syntax tree node, the context, and a continuation. The context can be
+%% examined and manipulated by functions such as `get_ctxt_user/1' and
+%% `set_ctxt_user/2'. The hook must return a "document" data structure
+%% (see {@link layout/2} and {@link best/2}); this may be constructed in
+%% part or in whole by applying the continuation function. For example,
+%% the following is a trivial hook:
+%% ```
+%%     fun (Node, Ctxt, Cont) -> Cont(Node, Ctxt) end
+%% '''
+%% which yields the same result as if no hook was given.
+%% The following, however:
+%% ```
+%%     fun (Node, Ctxt, Cont) ->
+%%         Doc = Cont(Node, Ctxt),
+%%         prettypr:beside(prettypr:text("<b>"),
+%%                         prettypr:beside(Doc,
+%%                                         prettypr:text("</b>")))
+%%     end
+%% '''
+%% will place the text of any annotated node (regardless of the
+%% annotation data) between HTML "boldface begin" and "boldface end"
+%% tags.
+%%
+%% @see erl_syntax
+%% @see format/1
+%% @see layout/2
+%% @see best/2
+%% @see get_ctxt_user/1
+%% @see set_ctxt_user/2
+
+format(Node, Options) ->
+    W = proplists:get_value(paper, Options, ?PAPER),
+    L = proplists:get_value(ribbon, Options, ?RIBBON),
+    prettypr:format(layout(Node, Options), W, L).
+
+
+%% =====================================================================
+%% @spec best(Tree::syntaxTree()) -> empty | document()
+%% @equiv best(Tree, [])
+
+best(Node) ->
+    best(Node, []).
+
+
+%% =====================================================================
+%% @spec best(Tree::syntaxTree(), Options::[term()]) ->
+%%           empty | document()
+%%
+%% @doc Creates a fixed "best" abstract layout for a syntax tree. This
+%% is similar to the `layout/2' function, except that here, the final
+%% layout has been selected with respect to the given options. The atom
+%% `empty' is returned if no such layout could be produced. For
+%% information on the options, see the `format/2' function.
+%%
+%% @see best/1
+%% @see layout/2
+%% @see format/2
+%% @see prettypr:best/3
+
+best(Node, Options) ->
+    W = proplists:get_value(paper, Options, ?PAPER),
+    L = proplists:get_value(ribbon, Options, ?RIBBON),
+    prettypr:best(layout(Node, Options), W, L).
+
+
+%% =====================================================================
+%% @spec layout(Tree::syntaxTree()) -> document()
+%% @equiv layout(Tree, [])
+
+layout(Node) ->
+    layout(Node, []).
+
+
+%% =====================================================================
+%% @spec layout(Tree::syntaxTree(), Options::[term()]) -> document()
+%%	    document() = prettypr:document()
+%%
+%% @doc Creates an abstract document layout for a syntax tree. The
+%% result represents a set of possible layouts (cf. module `prettypr').
+%% For information on the options, see {@link format/2}; note, however,
+%% that the `paper' and `ribbon' options are ignored by this function.
+%%
+%% This function provides a low-level interface to the pretty printer,
+%% returning a flexible representation of possible layouts, independent
+%% of the paper width eventually to be used for formatting. This can be
+%% included as part of another document and/or further processed
+%% directly by the functions in the `prettypr' module, or used in a hook
+%% function (see `format/2' for details).
+%%
+%% @see prettypr
+%% @see format/2
+%% @see layout/1
+
+layout(Node, Options) ->
+    lay(Node,
+	#ctxt{hook = proplists:get_value(hook, Options, ?NOHOOK),
+	      paper = proplists:get_value(paper, Options, ?PAPER),
+	      ribbon = proplists:get_value(ribbon, Options, ?RIBBON),
+	      user = proplists:get_value(user, Options)}).
+
+lay(Node, Ctxt) ->
+    case erl_syntax:get_ann(Node) of
+	[] ->
+	    %% Hooks are not called if there are no annotations.
+	    lay_1(Node, Ctxt);
+	_As ->
+	    case Ctxt#ctxt.hook of
+		?NOHOOK ->
+		    lay_1(Node, Ctxt);
+		Hook ->
+		    Hook(Node, Ctxt, fun lay_1/2)
+	    end
+    end.
+
+%% This handles attached comments:
+
+lay_1(Node, Ctxt) ->
+    case erl_syntax:has_comments(Node) of
+	true ->
+	    D1 = lay_2(Node, Ctxt),
+	    D2 = lay_postcomments(erl_syntax:get_postcomments(Node),
+				  D1),
+	    lay_precomments(erl_syntax:get_precomments(Node), D2);
+	false ->
+	    lay_2(Node, Ctxt)
+    end.
+
+%% For pre-comments, all padding is ignored.
+
+lay_precomments([], D) ->
+    D;
+lay_precomments(Cs, D) ->
+    above(floating(break(stack_comments(Cs, false)), -1, -1), D).
+
+%% For postcomments, individual padding is added.
+
+lay_postcomments([], D) ->
+    D;
+lay_postcomments(Cs, D) ->
+    beside(D, floating(break(stack_comments(Cs, true)), 1, 0)).
+
+%% Format (including padding, if `Pad' is `true', otherwise not)
+%% and stack the listed comments above each other,
+
+stack_comments([C | Cs], Pad) ->
+    D = stack_comment_lines(erl_syntax:comment_text(C)),
+    D1 = case Pad of
+	     true ->
+		 P = case erl_syntax:comment_padding(C) of
+			 none ->
+			     ?PADDING;
+			 P1 ->
+			     P1
+		     end,
+		 beside(text(spaces(P)), D);
+	     false ->
+		 D
+	 end,
+    case Cs of
+	[] ->
+	    D1;	   % done
+	_ ->
+	    above(D1, stack_comments(Cs, Pad))
+    end;
+stack_comments([], _) ->
+    empty().
+
+%% Stack lines of text above each other and prefix each string in
+%% the list with a single `%' character.
+
+stack_comment_lines([S | Ss]) ->
+    D = text(add_comment_prefix(S)),
+    case Ss of
+	[] ->
+	    D;
+	_ ->
+	    above(D, stack_comment_lines(Ss))
+    end;
+stack_comment_lines([]) ->
+    empty().
+
+add_comment_prefix(S) ->
+    [$% | S].
+
+%% This part ignores annotations and comments:
+
+lay_2(Node, Ctxt) ->
+    case erl_syntax:type(Node) of
+	%% We list literals and other common cases first.
+	
+	variable ->
+	    text(erl_syntax:variable_literal(Node));
+	
+	atom ->
+	    text(erl_syntax:atom_literal(Node));
+	
+	integer ->
+	    text(erl_syntax:integer_literal(Node));
+
+	float ->
+	    text(tidy_float(erl_syntax:float_literal(Node)));
+	
+	char ->
+	    text(erl_syntax:char_literal(Node));
+	
+	string ->
+	    lay_string(erl_syntax:string_literal(Node), Ctxt);
+
+	nil ->
+	    text("[]");
+
+	tuple ->
+	    Es = seq(erl_syntax:tuple_elements(Node),
+		     floating(text(",")), reset_prec(Ctxt),
+		     fun lay/2),
+	    beside(floating(text("{")),
+		   beside(par(Es),
+			  floating(text("}"))));
+	
+	list ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    Node1 = erl_syntax:compact_list(Node),
+	    D1 = par(seq(erl_syntax:list_prefix(Node1),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    D = case erl_syntax:list_suffix(Node1) of
+		    none ->
+			beside(D1, floating(text("]")));
+		    S ->
+			follow(D1,
+			       beside(
+				 floating(text("| ")),
+				 beside(lay(S, Ctxt1),
+					floating(text("]")))))
+		end,
+	    beside(floating(text("[")), D);
+
+	operator ->
+	    floating(text(erl_syntax:operator_literal(Node)));
+	
+	infix_expr ->
+	    Operator = erl_syntax:infix_expr_operator(Node),
+	    {PrecL, Prec, PrecR} =
+		case erl_syntax:type(Operator) of
+		    operator ->
+			inop_prec(
+			  erl_syntax:operator_name(Operator));
+		    _ ->
+			{0, 0, 0}
+		end,
+	    D1 = lay(erl_syntax:infix_expr_left(Node),
+		     set_prec(Ctxt, PrecL)),
+	    D2 = lay(Operator, reset_prec(Ctxt)),
+	    D3 = lay(erl_syntax:infix_expr_right(Node),
+		     set_prec(Ctxt, PrecR)),
+	    D4 = par([D1, D2, D3], Ctxt#ctxt.sub_indent),
+	    maybe_parentheses(D4, Prec, Ctxt);
+	
+	prefix_expr ->
+	    Operator = erl_syntax:prefix_expr_operator(Node),
+	    {{Prec, PrecR}, Name} =
+		case erl_syntax:type(Operator) of
+		    operator ->
+			N = erl_syntax:operator_name(Operator),
+			{preop_prec(N), N};
+		    _ ->
+			{{0, 0}, any}
+		end,
+	    D1 = lay(Operator, reset_prec(Ctxt)),
+	    D2 = lay(erl_syntax:prefix_expr_argument(Node),
+		     set_prec(Ctxt, PrecR)),
+	    D3 = case Name of
+		     '+' ->
+			 beside(D1, D2);
+		     '-' ->
+			 beside(D1, D2);
+		     _ ->
+			 par([D1, D2], Ctxt#ctxt.sub_indent)
+		 end,
+	    maybe_parentheses(D3, Prec, Ctxt);
+	
+	application ->
+	    {PrecL, Prec} = func_prec(),
+	    D = lay(erl_syntax:application_operator(Node),
+		    set_prec(Ctxt, PrecL)),
+	    As = seq(erl_syntax:application_arguments(Node),
+		     floating(text(",")), reset_prec(Ctxt),
+		     fun lay/2),
+%% 	    D1 = beside(D, beside(text("("),
+%% 				  beside(par(As),
+%% 					 floating(text(")"))))),
+	    D1 = beside(D, beside(text("("),
+				  beside(par(As),
+					 floating(text(")"))))),
+	    maybe_parentheses(D1, Prec, Ctxt);
+	
+	match_expr ->
+	    {PrecL, Prec, PrecR} = inop_prec('='),
+	    D1 = lay(erl_syntax:match_expr_pattern(Node),
+		     set_prec(Ctxt, PrecL)),
+	    D2 = lay(erl_syntax:match_expr_body(Node),
+		     set_prec(Ctxt, PrecR)),
+	    D3 = follow(beside(D1, floating(text(" ="))), D2,
+			Ctxt#ctxt.break_indent),
+	    maybe_parentheses(D3, Prec, Ctxt);
+
+	underscore ->
+	    text("_");
+
+	clause ->
+	    %% The style used for a clause depends on its context
+	    Ctxt1 = (reset_prec(Ctxt))#ctxt{clause = undefined},
+	    D1 = par(seq(erl_syntax:clause_patterns(Node),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    D2 = case erl_syntax:clause_guard(Node) of
+		     none ->
+			 none;
+		     G ->
+			 lay(G, Ctxt1)
+		 end,
+	    D3 = sep(seq(erl_syntax:clause_body(Node),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    case Ctxt#ctxt.clause of
+		fun_expr ->
+		    make_fun_clause(D1, D2, D3, Ctxt);
+		{function, N} ->
+		    make_fun_clause(N, D1, D2, D3, Ctxt);
+		if_expr ->
+		    make_if_clause(D1, D2, D3, Ctxt);
+		cond_expr ->
+		    make_if_clause(D1, D2, D3, Ctxt);
+		case_expr ->
+		    make_case_clause(D1, D2, D3, Ctxt);
+		receive_expr ->
+		    make_case_clause(D1, D2, D3, Ctxt);
+		try_expr ->
+		    make_case_clause(D1, D2, D3, Ctxt);
+		{rule, N} ->
+		    make_rule_clause(N, D1, D2, D3, Ctxt);
+		undefined ->
+		    %% If a clause is formatted out of context, we
+		    %% use a "fun-expression" clause style.
+		    make_fun_clause(D1, D2, D3, Ctxt)
+	    end;
+
+	function ->
+	    %% Comments on the name itself will be repeated for each
+	    %% clause, but that seems to be the best way to handle it.
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:function_name(Node), Ctxt1),
+	    D2 = lay_clauses(erl_syntax:function_clauses(Node),
+			     {function, D1}, Ctxt1),
+	    beside(D2, floating(text(".")));
+
+	case_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:case_expr_argument(Node), Ctxt1),
+	    D2 = lay_clauses(
+		   erl_syntax:case_expr_clauses(Node),
+		   case_expr, Ctxt1),
+	    sep([par([follow(text("case"), D1, Ctxt1#ctxt.sub_indent),
+		      text("of")],
+		     Ctxt1#ctxt.break_indent),
+		 nest(Ctxt1#ctxt.sub_indent, D2),
+		 text("end")]);
+	
+	if_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D = lay_clauses(erl_syntax:if_expr_clauses(Node),
+			    if_expr, Ctxt1),
+	    sep([follow(text("if"), D, Ctxt1#ctxt.sub_indent),
+		 text("end")]);
+
+	cond_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D = lay_clauses(erl_syntax:cond_expr_clauses(Node),
+			    cond_expr, Ctxt1),
+	    sep([text("cond"),
+		 nest(Ctxt1#ctxt.sub_indent, D),
+		 text("end")]);
+
+	fun_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D = lay_clauses(erl_syntax:fun_expr_clauses(Node),
+			       fun_expr, Ctxt1),
+	    sep([follow(text("fun"), D, Ctxt1#ctxt.sub_indent),
+		 text("end")]);
+
+	module_qualifier ->
+	    {PrecL, _Prec, PrecR} = inop_prec(':'),
+	    D1 = lay(erl_syntax:module_qualifier_argument(Node),
+		     set_prec(Ctxt, PrecL)),
+	    D2 = lay(erl_syntax:module_qualifier_body(Node),
+		     set_prec(Ctxt, PrecR)),
+	    beside(D1, beside(text(":"), D2));
+
+	qualified_name ->
+	    Ss = erl_syntax:qualified_name_segments(Node),
+	    lay_qualified_name(Ss, Ctxt);
+
+	%%
+	%% The rest is in alphabetical order
+	%%
+
+	arity_qualifier ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:arity_qualifier_body(Node), Ctxt1),
+	    D2 = lay(erl_syntax:arity_qualifier_argument(Node), Ctxt1),
+	    beside(D1, beside(text("/"), D2));
+
+	attribute ->
+	    %% The attribute name and arguments are formatted similar to
+	    %% a function call, but prefixed with a "-" and followed by
+	    %% a period. If the arguments is `none', we only output the
+	    %% attribute name, without following parentheses.
+	    Ctxt1 = reset_prec(Ctxt),
+	    N = erl_syntax:attribute_name(Node),
+	    D = case erl_syntax:attribute_arguments(Node) of
+		    none ->
+			lay(N, Ctxt1);
+		    Args ->
+			As = seq(Args, floating(text(",")), Ctxt1,
+				 fun lay/2),
+			beside(lay(N, Ctxt1),
+			       beside(text("("),
+				      beside(par(As),
+					     floating(text(")")))))
+		end,
+	    beside(floating(text("-")), beside(D, floating(text("."))));
+
+	binary ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    Es = seq(erl_syntax:binary_fields(Node),
+		     floating(text(",")), Ctxt1, fun lay/2),
+	    beside(floating(text("<<")),
+		   beside(par(Es), floating(text(">>"))));
+
+	binary_field ->
+	    Ctxt1 = set_prec(Ctxt, max_prec()),
+	    D1 = lay(erl_syntax:binary_field_body(Node), Ctxt1),
+	    D2 = case erl_syntax:binary_field_types(Node) of
+		     [] ->
+			 empty();
+		     Ts ->
+			 beside(floating(text("/")),
+				lay_bit_types(Ts, Ctxt1))
+		 end,
+	    beside(D1, D2);
+
+	block_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    Es = seq(erl_syntax:block_expr_body(Node),
+		     floating(text(",")), Ctxt1, fun lay/2),
+	    sep([text("begin"),
+		 nest(Ctxt1#ctxt.sub_indent, sep(Es)),
+		 text("end")]);
+
+	catch_expr ->
+	    {Prec, PrecR} = preop_prec('catch'),
+	    D = lay(erl_syntax:catch_expr_body(Node),
+		    set_prec(Ctxt, PrecR)),
+	    D1 = follow(text("catch"), D, Ctxt#ctxt.sub_indent),
+	    maybe_parentheses(D1, Prec, Ctxt);
+
+	class_qualifier ->
+	    Ctxt1 = set_prec(Ctxt, max_prec()),
+	    D1 = lay(erl_syntax:class_qualifier_argument(Node), Ctxt1),
+	    D2 = lay(erl_syntax:class_qualifier_body(Node), Ctxt1),
+	    beside(D1, beside(text(":"), D2));
+
+	comment ->
+	    D = stack_comment_lines(
+		  erl_syntax:comment_text(Node)),
+	    %% Default padding for standalone comments is empty.
+	    case erl_syntax:comment_padding(Node) of
+		none ->
+		    floating(break(D));
+		P ->
+		    floating(break(beside(text(spaces(P)), D)))
+	    end;
+
+	conjunction ->
+	    par(seq(erl_syntax:conjunction_body(Node),
+		    floating(text(",")), reset_prec(Ctxt),
+		    fun lay/2));
+
+	disjunction ->
+	    %% For clarity, we don't paragraph-format
+	    %% disjunctions; only conjunctions (see above).
+	    sep(seq(erl_syntax:disjunction_body(Node),
+		    floating(text(";")), reset_prec(Ctxt),
+		    fun lay/2));
+	    
+	error_marker ->
+	    E = erl_syntax:error_marker_info(Node),
+	    beside(text("** "),
+		   beside(lay_error_info(E, reset_prec(Ctxt)),
+			  text(" **")));
+
+	eof_marker ->
+	    empty();
+	
+	form_list ->
+	    Es = seq(erl_syntax:form_list_elements(Node), none,
+		     reset_prec(Ctxt), fun lay/2),
+	    vertical_sep(text(""), Es);
+
+	generator ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:generator_pattern(Node), Ctxt1),
+	    D2 = lay(erl_syntax:generator_body(Node), Ctxt1),
+	    par([D1, beside(text("<- "), D2)], Ctxt1#ctxt.break_indent);
+
+	binary_generator ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:binary_generator_pattern(Node), Ctxt1),
+	    D2 = lay(erl_syntax:binary_generator_body(Node), Ctxt1),
+	    par([D1, beside(text("<= "), D2)], Ctxt1#ctxt.break_indent);
+
+	implicit_fun ->
+	    D = lay(erl_syntax:implicit_fun_name(Node),
+		    reset_prec(Ctxt)),
+	    beside(floating(text("fun ")), D);
+
+	list_comp ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:list_comp_template(Node), Ctxt1),
+	    D2 = par(seq(erl_syntax:list_comp_body(Node),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    beside(floating(text("[")),
+		   par([D1, beside(floating(text("|| ")),
+				   beside(D2, floating(text("]"))))]));
+
+	binary_comp ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:binary_comp_template(Node), Ctxt1),
+	    D2 = par(seq(erl_syntax:binary_comp_body(Node),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    beside(floating(text("<< ")),
+		   par([D1, beside(floating(text(" || ")),
+				   beside(D2, floating(text(" >>"))))]));
+
+	macro ->
+	    %% This is formatted similar to a normal function call, but
+	    %% prefixed with a "?".
+	    Ctxt1 = reset_prec(Ctxt),
+	    N = erl_syntax:macro_name(Node),
+	    D = case erl_syntax:macro_arguments(Node) of
+		    none->
+			lay(N, Ctxt1);
+		    Args ->
+			As = seq(Args, floating(text(",")),
+				 set_prec(Ctxt1, max_prec()), fun lay/2),
+			beside(lay(N, Ctxt1),
+			       beside(text("("),
+				      beside(par(As),
+					     floating(text(")")))))
+		end,
+	    D1 = beside(floating(text("?")), D),
+	    maybe_parentheses(D1, 0, Ctxt);    % must be conservative!
+
+	parentheses ->
+	    D = lay(erl_syntax:parentheses_body(Node),
+		    reset_prec(Ctxt)),
+	    lay_parentheses(D, Ctxt);
+
+	query_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D = lay(erl_syntax:query_expr_body(Node), Ctxt1),
+	    sep([text("query"),
+		 nest(Ctxt1#ctxt.sub_indent, D),
+		 text("end")]);
+
+	receive_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay_clauses(
+		   erl_syntax:receive_expr_clauses(Node),
+		   receive_expr, Ctxt1),
+	    D2 = case erl_syntax:receive_expr_timeout(Node) of
+		     none ->
+			 D1;
+		     T ->
+			 D3 = lay(T, Ctxt1),
+			 A = erl_syntax:receive_expr_action(Node),
+			 D4 = sep(seq(A, floating(text(",")),
+				      Ctxt1, fun lay/2)),
+			 sep([D1,
+			      follow(floating(text("after")),
+				     append_clause_body(D4, D3,
+							Ctxt1),
+				     Ctxt1#ctxt.sub_indent)])
+		 end,
+	    sep([text("receive"),
+		 nest(Ctxt1#ctxt.sub_indent, D2),
+		 text("end")]);
+
+	record_access ->
+	    {PrecL, Prec, PrecR} = inop_prec('#'),
+	    D1 = lay(erl_syntax:record_access_argument(Node),
+		     set_prec(Ctxt, PrecL)),
+	    D2 = beside(
+		   floating(text(".")),
+		   lay(erl_syntax:record_access_field(Node),
+		       set_prec(Ctxt, PrecR))),
+	    D3 = case erl_syntax:record_access_type(Node) of
+		     none ->
+			 D2;
+		     T ->
+			 beside(beside(floating(text("#")),
+				       lay(T, reset_prec(Ctxt))),
+				D2)
+		 end,
+	    maybe_parentheses(beside(D1, D3), Prec, Ctxt);
+
+	record_expr ->
+	    {PrecL, Prec, _} = inop_prec('#'),	  
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:record_expr_type(Node), Ctxt1),
+	    D2 = par(seq(erl_syntax:record_expr_fields(Node),
+			 floating(text(",")), Ctxt1,
+			 fun lay/2)),
+	    D3 = beside(beside(floating(text("#")), D1),
+			beside(text("{"),
+			       beside(D2, floating(text("}"))))),
+	    D4 = case erl_syntax:record_expr_argument(Node) of
+		     none ->
+			 D3;
+		     A ->
+			 beside(lay(A, set_prec(Ctxt, PrecL)), D3)
+		 end,
+	    maybe_parentheses(D4, Prec, Ctxt);
+	
+	record_field ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:record_field_name(Node), Ctxt1),
+	    case erl_syntax:record_field_value(Node) of
+		none ->
+		    D1;
+		V ->
+		    par([D1, floating(text("=")), lay(V, Ctxt1)],
+			Ctxt1#ctxt.break_indent)
+	    end;
+
+	record_index_expr ->
+	    {Prec, PrecR} = preop_prec('#'),	
+	    D1 = lay(erl_syntax:record_index_expr_type(Node),
+		     reset_prec(Ctxt)),
+	    D2 = lay(erl_syntax:record_index_expr_field(Node),
+		     set_prec(Ctxt, PrecR)),
+	    D3 = beside(beside(floating(text("#")), D1),
+			beside(floating(text(".")), D2)),
+	    maybe_parentheses(D3, Prec, Ctxt);
+
+	rule ->
+	    %% Comments on the name will be repeated; cf.
+	    %% `function'.
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = lay(erl_syntax:rule_name(Node), Ctxt1),
+	    D2 = lay_clauses(erl_syntax:rule_clauses(Node),
+			     {rule, D1}, Ctxt1),
+	    beside(D2, floating(text(".")));
+
+	size_qualifier ->
+	    Ctxt1 = set_prec(Ctxt, max_prec()),
+	    D1 = lay(erl_syntax:size_qualifier_body(Node), Ctxt1),
+	    D2 = lay(erl_syntax:size_qualifier_argument(Node), Ctxt1),
+	    beside(D1, beside(text(":"), D2));
+
+	text ->
+	    text(erl_syntax:text_string(Node));
+
+	try_expr ->
+	    Ctxt1 = reset_prec(Ctxt),
+	    D1 = sep(seq(erl_syntax:try_expr_body(Node),
+			 floating(text(",")), Ctxt1, fun lay/2)),
+	    Es0 = [text("end")],
+	    Es1 = case erl_syntax:try_expr_after(Node) of
+		      [] -> Es0;
+		      As ->
+			  D2 = sep(seq(As, floating(text(",")), Ctxt1,
+				       fun lay/2)),
+			  [text("after"),
+			   nest(Ctxt1#ctxt.sub_indent, D2)
+			   | Es0]
+		  end,
+	    Es2 = case erl_syntax:try_expr_handlers(Node) of
+		      [] -> Es1;
+		      Hs ->
+			  D3 = lay_clauses(Hs, try_expr, Ctxt1),
+			  [text("catch"),
+			   nest(Ctxt1#ctxt.sub_indent, D3)
+			   | Es1]
+		  end,
+	    Es3 = case erl_syntax:try_expr_clauses(Node) of
+		      [] -> Es2;
+		      Cs ->
+			  D4 = lay_clauses(Cs, try_expr, Ctxt1),
+			  [text("of"),
+			   nest(Ctxt1#ctxt.sub_indent, D4)
+			   | Es2]
+		  end,
+	    sep([par([follow(text("try"), D1, Ctxt1#ctxt.sub_indent),
+		      hd(Es3)])
+		 | tl(Es3)]);
+
+	warning_marker ->
+	    E = erl_syntax:warning_marker_info(Node),
+	    beside(text("%% WARNING: "),
+		   lay_error_info(E, reset_prec(Ctxt)))
+    end.
+
+lay_parentheses(D, _Ctxt) ->
+    beside(floating(text("(")), beside(D, floating(text(")")))).
+
+maybe_parentheses(D, Prec, Ctxt) ->
+    case Ctxt#ctxt.prec of
+	P when P > Prec ->
+	    lay_parentheses(D, Ctxt);
+	_ ->
+	    D
+    end.
+
+lay_qualified_name([S | Ss1] = Ss, Ctxt) ->
+    case erl_syntax:type(S) of
+	atom ->
+	    case erl_syntax:atom_value(S) of
+		'' ->
+		    beside(text("."),
+			   lay_qualified_name_1(Ss1, Ctxt));
+		_ ->
+		    lay_qualified_name_1(Ss, Ctxt)
+	    end;
+	_ ->
+	    lay_qualified_name_1(Ss, Ctxt)
+    end.
+
+lay_qualified_name_1([S], Ctxt) ->
+    lay(S, Ctxt);
+lay_qualified_name_1([S | Ss], Ctxt) ->
+    beside(lay(S, Ctxt), beside(text("."),
+				lay_qualified_name_1(Ss, Ctxt))).
+
+lay_string(S, Ctxt) ->
+    %% S includes leading/trailing double-quote characters. The segment
+    %% width is 2/3 of the ribbon width - this seems to work well.
+    W = (Ctxt#ctxt.ribbon * 2) div 3,
+    lay_string_1(S, length(S), W).
+
+lay_string_1(S, L, W) when L > W, W > 0 ->
+    %% Note that L is the minimum, not the exact, printed length.
+    case split_string(S, W - 1, L) of
+	{_S1, ""} ->
+	    text(S);
+	{S1, S2} ->
+	    above(text(S1 ++ "\""),
+		  lay_string_1([$" | S2], L - W + 1, W))  %" stupid emacs
+    end;
+lay_string_1(S, _L, _W) ->
+    text(S).
+
+split_string(Xs, N, L) ->
+    split_string_1(Xs, N, L, []).
+
+%% We only split strings at whitespace, if possible. We must make sure
+%% we do not split an escape sequence.
+
+split_string_1([$\s | Xs], N, L, As) when N =< 0, L >= 5 ->
+    {lists:reverse([$\s | As]), Xs};
+split_string_1([$\t | Xs], N, L, As) when N =< 0, L >= 5 ->
+    {lists:reverse([$t, $\\ | As]), Xs};
+split_string_1([$\n | Xs], N, L, As) when N =< 0, L >= 5 ->
+    {lists:reverse([$n, $\\ | As]), Xs};
+split_string_1([$\\ | Xs], N, L, As) ->
+    split_string_2(Xs, N - 1, L - 1, [$\\ | As]);
+split_string_1(Xs, N, L, As) when N =< -10, L >= 5 ->
+    {lists:reverse(As), Xs};
+split_string_1([X | Xs], N, L, As) ->
+    split_string_1(Xs, N - 1, L - 1, [X | As]);
+split_string_1([], _N, _L, As) ->
+    {lists:reverse(As), ""}.
+
+split_string_2([$^, X | Xs], N, L, As) ->
+    split_string_1(Xs, N - 2, L - 2, [X, $^ | As]);
+split_string_2([X1, X2, X3 | Xs], N, L, As) when
+  X1 >= $0, X1 =< $7, X2 >= $0, X2 =< $7, X3 >= $0, X3 =< $7 ->
+    split_string_1(Xs, N - 3, L - 3, [X3, X2, X1 | As]);
+split_string_2([X1, X2 | Xs], N, L, As) when 
+  X1 >= $0, X1 =< $7, X2 >= $0, X2 =< $7 ->
+    split_string_1(Xs, N - 2, L - 2, [X2, X1 | As]);
+split_string_2([X | Xs], N, L, As) ->
+    split_string_1(Xs, N - 1, L - 1, [X | As]).
+
+%% Note that there is nothing in `lay_clauses' that actually requires
+%% that the elements have type `clause'; it just sets up the proper
+%% context and arranges the elements suitably for clauses.
+
+lay_clauses(Cs, Type, Ctxt) ->
+    vertical(seq(Cs, floating(text(";")),
+		 Ctxt#ctxt{clause = Type},
+		 fun lay/2)).
+
+%% Note that for the clause-making functions, the guard argument
+%% can be `none', which has different interpretations in different
+%% contexts.
+
+make_fun_clause(P, G, B, Ctxt) ->
+    make_fun_clause(none, P, G, B, Ctxt).
+
+make_fun_clause(N, P, G, B, Ctxt) ->
+    D = make_fun_clause_head(N, P, Ctxt),
+    make_case_clause(D, G, B, Ctxt).
+
+make_fun_clause_head(N, P, Ctxt) ->
+    D = lay_parentheses(P, Ctxt),
+    if N =:= none ->
+	    D;
+       true ->
+	    beside(N, D)
+    end.
+
+make_rule_clause(N, P, G, B, Ctxt) ->
+    D = make_fun_clause_head(N, P, Ctxt),
+    append_rule_body(B, append_guard(G, D, Ctxt), Ctxt).
+
+make_case_clause(P, G, B, Ctxt) ->
+    append_clause_body(B, append_guard(G, P, Ctxt), Ctxt).
+
+make_if_clause(_P, G, B, Ctxt) ->
+    %% We ignore the patterns; they should be empty anyway.
+    G1 = if G =:= none ->
+		 text("true");
+	    true ->
+		 G
+	 end,
+    append_clause_body(B, G1, Ctxt).
+
+append_clause_body(B, D, Ctxt) ->
+    append_clause_body(B, D, floating(text(" ->")), Ctxt).
+
+append_rule_body(B, D, Ctxt) ->
+    append_clause_body(B, D, floating(text(" :-")), Ctxt).
+
+append_clause_body(B, D, S, Ctxt) ->
+    sep([beside(D, S), nest(Ctxt#ctxt.break_indent, B)]).
+
+append_guard(none, D, _) ->
+    D;
+append_guard(G, D, Ctxt) ->
+    par([D, follow(text("when"), G, Ctxt#ctxt.sub_indent)],
+	Ctxt#ctxt.break_indent).
+
+lay_bit_types([T], Ctxt) ->
+    lay(T, Ctxt);
+lay_bit_types([T | Ts], Ctxt) ->
+    beside(lay(T, Ctxt),
+	   beside(floating(text("-")),
+		  lay_bit_types(Ts, Ctxt))).
+
+lay_error_info({L, M, T}=T0, Ctxt) when is_integer(L), is_atom(M) ->
+    case catch M:format_error(T) of
+	S when is_list(S) ->
+	    if L > 0 ->
+		    beside(text(io_lib:format("~w: ",[L])), text(S));
+	       true ->
+		    text(S)
+	    end;
+	_ ->
+	    lay_concrete(T0, Ctxt)
+    end;
+lay_error_info(T, Ctxt) ->
+    lay_concrete(T, Ctxt).
+
+lay_concrete(T, Ctxt) ->
+    lay(erl_syntax:abstract(T), Ctxt).
+
+seq([H | T], Separator, Ctxt, Fun) ->
+    case T of
+	[] ->
+	    [Fun(H, Ctxt)];
+	_ ->
+	    [maybe_append(Separator, Fun(H, Ctxt))
+	     | seq(T, Separator, Ctxt, Fun)]
+    end;
+seq([], _, _, _) ->
+    [empty()].
+
+maybe_append(none, D) ->
+    D;
+maybe_append(Suffix, D) ->
+    beside(D, Suffix).
+
+vertical([D]) ->
+    D;
+vertical([D | Ds]) ->
+    above(D, vertical(Ds));
+vertical([]) ->
+    [].
+
+vertical_sep(_Sep, [D]) ->
+    D;
+vertical_sep(Sep, [D | Ds]) ->
+    above(above(D, Sep), vertical_sep(Sep, Ds));
+vertical_sep(_Sep, []) ->
+    [].
+
+spaces(N) when N > 0 ->
+    [$\040 | spaces(N - 1)];
+spaces(_) ->
+    [].
+
+tidy_float([$., C | Cs]) ->
+    [$., C | tidy_float_1(Cs)];  % preserve first decimal digit
+tidy_float([$e | _] = Cs) ->
+    tidy_float_2(Cs);
+tidy_float([C | Cs]) ->
+    [C | tidy_float(Cs)];
+tidy_float([]) ->
+    [].
+
+tidy_float_1([$0, $0, $0 | Cs]) ->
+    tidy_float_2(Cs);    % cut mantissa at three consecutive zeros.
+tidy_float_1([$e | _] = Cs) ->
+    tidy_float_2(Cs);
+tidy_float_1([C | Cs]) ->
+    [C | tidy_float_1(Cs)];
+tidy_float_1([]) ->
+    [].
+
+tidy_float_2([$e, $+, $0]) -> [];
+tidy_float_2([$e, $+, $0 | Cs]) -> tidy_float_2([$e, $+ | Cs]);
+tidy_float_2([$e, $+ | _] = Cs) -> Cs;
+tidy_float_2([$e, $-, $0]) -> [];
+tidy_float_2([$e, $-, $0 | Cs]) -> tidy_float_2([$e, $- | Cs]);
+tidy_float_2([$e, $- | _] = Cs) -> Cs;
+tidy_float_2([$e | Cs]) -> tidy_float_2([$e, $+ | Cs]);
+tidy_float_2([_C | Cs]) -> tidy_float_2(Cs);
+tidy_float_2([]) -> [].
+
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/erl_recomment.erl b/lib/syntax_tools/src/erl_recomment.erl
new file mode 100644
index 0000000000..62ec7da200
--- /dev/null
+++ b/lib/syntax_tools/src/erl_recomment.erl
@@ -0,0 +1,757 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1997-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Inserting comments into abstract Erlang syntax trees
+%%
+%% <p>This module contains functions for inserting comments, described
+%% by position, indentation and text, as attachments on an abstract
+%% syntax tree, at the correct places.</p>
+
+-module(erl_recomment).
+
+-export([recomment_forms/2, quick_recomment_forms/2, recomment_tree/2]).
+
+
+%% =====================================================================
+%% @spec quick_recomment_forms(Forms, Comments::[Comment]) ->
+%%           syntaxTree()
+%%
+%%	    Forms = syntaxTree() | [syntaxTree()]
+%%	    Comment = {Line, Column, Indentation, Text}
+%%	    Line = integer()
+%%	    Column = integer()
+%%	    Indentation = integer()
+%%	    Text = [string()]
+%%
+%% @doc Like {@link recomment_forms/2}, but only inserts top-level
+%% comments. Comments within function definitions or declarations
+%% ("forms") are simply ignored.
+
+quick_recomment_forms(Tree, Cs) ->
+    recomment_forms(Tree, Cs, false).
+
+
+%% =====================================================================
+%% @spec recomment_forms(Forms, Comments::[Comment]) -> syntaxTree()
+%%
+%%	    syntaxTree() = erl_syntax:syntaxTree()
+%%	    Forms = syntaxTree() | [syntaxTree()]
+%%	    Comment = {Line, Column, Indentation, Text}
+%%	    Line = integer()
+%%	    Column = integer()
+%%	    Indentation = integer()
+%%	    Text = [string()]
+%%
+%% @doc Attaches comments to the syntax tree/trees representing a
+%% program. The given <code>Forms</code> should be a single syntax tree
+%% of type <code>form_list</code>, or a list of syntax trees
+%% representing "program forms". The syntax trees must contain valid
+%% position information (for details, see
+%% <code>recomment_tree/2</code>). The result is a corresponding syntax
+%% tree of type <code>form_list</code> in which all comments in the list
+%% <code>Comments</code> have been attached at the proper places.
+%%
+%% <p>Assuming <code>Forms</code> represents a program (or any sequence
+%% of "program forms"), any comments whose first lines are not directly
+%% associated with a specific program form will become standalone
+%% comments inserted between the neighbouring program forms.
+%% Furthermore, comments whose column position is less than or equal to
+%% one will not be attached to a program form that begins at a
+%% conflicting line number (this can happen with preprocessor-generated
+%% <code>line</code>-attributes).</p>
+%%
+%% <p>If <code>Forms</code> is a syntax tree of some other type than
+%% <code>form_list</code>, the comments will be inserted directly using
+%% <code>recomment_tree/2</code>, and any comments left over from that
+%% process are added as postcomments on the result.</p>
+%%
+%% <p>Entries in <code>Comments</code> represent multi-line comments.
+%% For each entry, <code>Line</code> is the line number and
+%% <code>Column</code> the left column of the comment (the column of the
+%% first comment-introducing "<code>%</code>" character).
+%% <code>Indentation</code> is the number of character positions between
+%% the last non-whitespace character before the comment (or the left
+%% margin) and the left column of the comment. <code>Text</code> is a
+%% list of strings representing the consecutive comment lines in
+%% top-down order, where each string contains all characters following
+%% (but not including) the comment-introducing "<code>%</code>" and up
+%% to (but not including) the terminating newline. (Cf. module
+%% <code>erl_comment_scan</code>.)</p>
+%%
+%% <p>Evaluation exits with reason <code>{bad_position, Pos}</code> if
+%% the associated position information <code>Pos</code> of some subtree
+%% in the input does not have a recognizable format, or with reason
+%% <code>{bad_tree, L, C}</code> if insertion of a comment at line
+%% <code>L</code>, column <code>C</code>, fails because the tree
+%% structure is ill-formed.</p>
+%%
+%% @see erl_comment_scan
+%% @see recomment_tree/2
+%% @see quick_recomment_forms/2
+
+recomment_forms(Tree, Cs) ->
+    recomment_forms(Tree, Cs, true).
+
+recomment_forms(Tree, Cs, Insert) when is_list(Tree) ->
+    recomment_forms(erl_syntax:form_list(Tree), Cs, Insert);
+recomment_forms(Tree, Cs, Insert) ->
+    case erl_syntax:type(Tree) of
+	form_list ->
+	    Tree1 = erl_syntax:flatten_form_list(Tree),
+	    Node = build_tree(Tree1),
+
+	    %% Here we make a small assumption about the substructure of
+	    %% a `form_list' tree: it has exactly one group of subtrees.
+	    [Node1] = node_subtrees(Node),
+	    List = filter_forms(node_subtrees(Node1)),
+	    List1 = recomment_forms_1(Cs, List, Insert),
+	    revert_tree(set_node_subtrees(Node,
+					  [set_node_subtrees(Node1,
+							     List1)]));
+	_ ->
+	    %% Not a form list - just call `recomment_tree' and
+	    %% append any leftover comments.
+	    {Tree1, Cs1} = recomment_tree(Tree, Cs),
+	    revert_tree(append_comments(Cs1, Tree1))
+    end.
+
+append_comments([C | Cs], Tree) ->
+    append_comments(Cs, node_add_postcomment(C, Tree));
+append_comments([], Tree) ->
+    Tree.
+
+%% This part goes over each comment in turn and inserts it into the
+%% proper place in the given list of program forms:
+
+recomment_forms_1([C | Cs], Ns, Insert) ->
+    Ns1 = recomment_forms_2(C, Ns, Insert),
+    recomment_forms_1(Cs, Ns1, Insert);
+recomment_forms_1([], Ns, _Insert) ->
+    Ns.
+
+recomment_forms_2(C, [N | Ns] = Nodes, Insert) ->
+    {L, Col, Ind, Text} = C,
+    Min = node_min(N),
+    Max = node_max(N),
+    Delta = comment_delta(Text),
+    Trailing = 
+	case Ns of
+	    [] -> true;
+	    [Next | _] -> L < node_min(Next) - 2
+	end,
+    if L > Max + 1 ; L =:= Max + 1, not Trailing ->
+	    [N | recomment_forms_2(C, Ns, Insert)];
+       L + Delta < Min - 1 ->
+	    %% At least one empty line between the current form
+	    %% and the comment, so we make it a standalone.
+	    [standalone_comment(C) | Nodes];
+       L < Min ->
+	    %% The comment line should be above this node.
+	    %% (This duplicates what insert/5 would have done.)
+	    [node_add_precomment(C, N) | Ns];
+       Col =< 1, L =< Min, L + Delta >= Min ->
+	    %% This is a conflict - the "first" token of the node
+	    %% overlaps with some comment line, but the comment
+	    %% started at column 1.
+	    N1 = standalone_comment(C),
+	    if L < Min ->
+		    [N1 | Nodes];
+	       true ->
+		    [N, N1 | Ns]
+	    end;
+       Insert =:= true ->
+	    [insert(N, L, Col, Ind, C) | Ns];
+       true ->
+	    Nodes    % skipping non-toplevel comment
+    end;
+recomment_forms_2(C, [], _Top) ->
+    [standalone_comment(C)].
+
+%% Creating a leaf node for a standalone comment. Note that we try to
+%% preserve the original starting column rather than the indentation.
+
+standalone_comment({L, Col, _Ind, Text}) ->
+    leaf_node(L, L + comment_delta(Text),
+	      erl_syntax:set_pos(erl_syntax:comment(Col - 1, Text), L)).
+
+%% Compute delta between first and last line of a comment, given
+%% the lines of text.
+
+comment_delta(Text) ->
+    case length(Text) of
+	N when N > 0 ->
+	    N - 1;
+	_ ->
+	    0    % avoid negative delta
+    end.
+
+%% This kills line information for program forms that do not come from
+%% the source file itself, but have been included by preprocessing. This
+%% way, comments will not be inserted into such parts by mistake.
+
+-record(filter, {file = undefined, line = 0}).
+
+filter_forms(Fs) ->
+    filter_forms(Fs, false, #filter{}).
+
+filter_forms([F | Fs], Kill, S) ->
+    case check_file_attr(F) of
+	{true, A1, A2} ->
+	    S1 = case S#filter.file of
+		     undefined ->
+			 S#filter{file = A1, line = A2};
+		     _ ->
+			 S
+		 end,
+	    if S1#filter.file =:= A1,
+	       S1#filter.line =< A2 ->
+		    [F | filter_forms(Fs, false,
+				      S1#filter{line = A2})];
+	       Kill =:= true ->
+		    [node_kill_range(F)
+		     | filter_forms(Fs, true, S1)];
+	       true ->
+		    [F | filter_forms(Fs, true, S1)]
+	    end;
+	false ->
+	    case Kill of
+		true ->
+		    [node_kill_range(F)
+		     | filter_forms(Fs, Kill, S)];
+		false ->
+		    [F | filter_forms(Fs, Kill, S)]
+	    end
+    end;
+filter_forms([], _, _) ->
+    [].
+
+%% This structure matching gets a bit painful...
+
+check_file_attr(F) ->
+    case node_type(F) of
+	tree_node ->
+	    case tree_node_type(F) of
+		attribute ->
+		    case node_subtrees(F) of
+			[L1, L2 | _] ->
+			    check_file_attr_1(L1, L2);
+			_ ->
+			    false
+		    end;
+		_ ->
+		    false
+	    end;
+	_ ->
+	    false
+    end.
+
+check_file_attr_1(L1, L2) ->
+    case node_subtrees(L1) of
+	[N1 | _] ->
+	    N2 = leaf_node_value(N1),
+	    case erl_syntax:type(N2) of
+		atom ->
+		    case erl_syntax:atom_value(N2) of
+			file ->
+			    check_file_attr_2(L2);
+			_ ->
+			    false
+		    end;
+		_ ->
+		    false
+	    end;
+	_ ->
+	    false
+    end.
+
+check_file_attr_2(L) ->
+    case node_subtrees(L) of
+	[N1, N2 | _] ->
+	    T1 = erl_syntax:concrete(revert_tree(N1)),
+	    T2 = erl_syntax:concrete(revert_tree(N2)),
+	    {true, T1, T2};
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec recomment_tree(Tree::syntaxTree(), Comments::[Comment]) ->
+%%           {syntaxTree(), [Comment]}
+%%
+%%	    Comment = {Line, Column, Indentation, Text}
+%%	    Line = integer()
+%%	    Column = integer()
+%%	    Indentation = integer()
+%%	    Text = [string()]
+%%
+%% @doc Attaches comments to a syntax tree. The result is a pair
+%% <code>{NewTree, Remainder}</code> where <code>NewTree</code> is the
+%% given <code>Tree</code> where comments from the list
+%% <code>Comments</code> have been attached at the proper places.
+%% <code>Remainder</code> is the list of entries in
+%% <code>Comments</code> which have not been inserted, because their
+%% line numbers are greater than those of any node in the tree. The
+%% entries in <code>Comments</code> are inserted in order; if two
+%% comments become attached to the same node, they will appear in the
+%% same order in the program text.
+%%
+%% <p>The nodes of the syntax tree must contain valid position
+%% information. This can be single integers, assumed to represent a line
+%% number, or 2- or 3-tuples where the first or second element is an
+%% integer, in which case the leftmost integer element is assumed to
+%% represent the line number. Line numbers less than one are ignored
+%% (usually, the default line number for newly created nodes is
+%% zero).</p>
+%%
+%% <p>For details on the <code>Line</code>, <code>Column</code> and
+%% <code>Indentation</code> fields, and the behaviour in case of errors,
+%% see <code>recomment_forms/2</code>.</p>
+%%
+%% @see recomment_forms/2
+
+recomment_tree(Tree, Cs) ->
+    {Tree1, Cs1} = insert_comments(Cs, build_tree(Tree)),
+    {revert_tree(Tree1), Cs1}.
+
+%% Comments are inserted in the tree one at a time. Note that this
+%% part makes no assumptions about how tree nodes and list nodes
+%% are nested; only `build_tree' and `revert_tree' knows about
+%% such things.
+    
+insert_comments(Cs, Node) ->
+    insert_comments(Cs, Node, []).
+
+insert_comments([C | Cs], Node, Cs1) ->
+    {L, Col, Ind, _Text} = C,
+    Max = node_max(Node),
+    if L =< Max ->
+	    insert_comments(Cs, insert(Node, L, Col, Ind, C),
+			    Cs1);
+       true ->
+	    insert_comments(Cs, Node, [C | Cs1])
+    end;
+insert_comments([], Node, Cs) ->
+    {Node, lists:reverse(Cs)}.
+
+%% Here, we assume that the comment is located on some line not
+%% below the last element of the given node.
+
+insert(Node, L, Col, Ind, C) ->
+    case node_type(Node) of
+	list_node ->
+	    %% We cannot attach comments directly to a list node.
+	    set_node_subtrees(Node,
+			      insert_in_list(node_subtrees(Node),
+					     L, Col, Ind, C));
+	_ ->
+	    %% We check if the comment belongs before, or inside
+	    %% the range of the current node.
+	    Min = node_min(Node),
+	    Max = node_max(Node),
+	    if L < Min ->
+		    %% The comment line should be above this node.
+		    node_add_precomment(C, Node);
+	       Min =:= Max  ->
+		    %% The whole node is on a single line (this
+		    %% should usually catch all leaf nodes), so we
+		    %% postfix the comment.
+		    node_add_postcomment(C, Node);
+	       true ->
+		    %% The comment should be inserted in the
+		    %% subrange of the node, i.e., attached either
+		    %% to the node itself, or to one of its
+		    %% subtrees.
+		    insert_1(Node, L, Col, Ind, C)
+	    end
+    end.
+
+insert_1(Node, L, Col, Ind, C) ->
+    case node_type(Node) of
+	tree_node ->
+	    %% Insert in one of the subtrees.
+	    set_node_subtrees(Node,
+			      insert_in_list(node_subtrees(Node),
+					     L, Col, Ind, C));
+	leaf_node ->
+	    %% Odd case: no components, but not on a single line.
+	    %% (Never mind anyway - just postfix the comment.)
+	    node_add_postcomment(C, Node)
+    end.
+
+%% We assume that there exists at least one tree node in some tree
+%% in the list; since we have decided to insert here, we're
+%% screwed if there isn't one.
+
+insert_in_list([Node | Ns], L, Col, Ind, C) ->
+    Max = node_max(Node),
+    
+    %% Get the `Min' of the next node that follows in the
+    %% flattened left-to-right order, or -1 (minus one) if no such
+    %% tree node exists.
+    NextMin = next_min_in_list(Ns),
+    
+    %% `NextMin' could be less than `Max', in inconsistent trees.
+    if NextMin < 0 ->
+	    %% There is no following leaf/tree node, so we try
+	    %% to insert at this node.
+	    insert_here(Node, L, Col, Ind, C, Ns);
+       L >= NextMin, NextMin >= Max ->
+	    %% Tend to select the later node, in case the next
+	    %% node should also match.
+	    insert_later(Node, L, Col, Ind, C, Ns);
+       L =< Max ->
+	    insert_here(Node, L, Col, Ind, C, Ns);
+       true ->
+	    insert_later(Node, L, Col, Ind, C, Ns)
+    end;
+insert_in_list([], L, Col, _, _) ->
+    exit({bad_tree, L, Col}).
+
+%% The comment belongs to the current subrange
+
+insert_here(Node, L, Col, Ind, C, Ns) ->
+    [insert(Node, L, Col, Ind, C) | Ns].
+
+%% The comment should be inserted later
+
+insert_later(Node, L, Col, Ind, C, Ns) ->
+    [Node | insert_in_list(Ns, L, Col, Ind, C)].
+
+%% `next_min_in_list' returns the `Min' field of the leftmost tree
+%% or leaf node in the given node list, or the integer -1 (minus
+%% one) if no such element exists.
+
+next_min_in_list(Ts) ->
+    next_min_in_list(Ts, []).
+
+next_min_in_list([T | Ts], Ack) ->
+    next_min_in_node(T, [Ts | Ack]);
+next_min_in_list([], [T | Ts]) ->
+    next_min_in_list(T, Ts);
+next_min_in_list([], []) ->
+    -1.
+
+next_min_in_node(Node, Ack) ->
+    case node_type(Node) of
+	leaf_node ->
+	    node_min(Node);
+	tree_node ->
+	    node_min(Node);
+	list_node ->
+	    next_min_in_list(node_subtrees(Node), Ack)
+    end.
+
+%% Building an extended syntax tree from an `erl_syntax' abstract
+%% syntax tree.
+
+build_tree(Node) ->
+    L = get_line(Node),
+    case erl_syntax:subtrees(Node) of
+	[] ->
+	    %% This guarantees that Min =< Max for the base case.
+	    leaf_node(L, L, Node);
+	Ts ->
+	    %% `Ts' is a list of lists of abstract terms.
+	    {Subtrees, Min, Max} = build_list_list(Ts),
+	    
+	    %% Include L, while preserving Min =< Max.
+	    tree_node(minpos(L, Min),
+		      max(L, Max),
+		      erl_syntax:type(Node),
+		      erl_syntax:get_attrs(Node),
+		      Subtrees)
+    end.
+
+%% Since `erl_syntax:subtrees' yields the components in
+%% left-to-right textual order, the line numbers should grow
+%% monotonically as the list is traversed, and the maximum line
+%% number of the list should therefore be the dito of the last
+%% component. However, we do not want to make such a strong
+%% assumption about the consistency of the line numbering, so we
+%% take the trouble to find the maximum line number in the subtree
+%% taken over all its elements.
+
+build_list(Ts) ->
+    build_list(Ts, 0, 0, []).
+
+build_list([T | Ts], Min, Max, Ack) ->
+    Node = build_tree(T),
+    Min1 = minpos(node_min(Node), Min),
+    Max1 = max(node_max(Node), Max),
+    build_list(Ts, Min1, Max1, [Node | Ack]);
+build_list([], Min, Max, Ack) ->
+    list_node(Min, Max, lists:reverse(Ack)).
+
+build_list_list(Ls) ->
+    build_list_list(Ls, 0, 0, []).
+
+build_list_list([L | Ls], Min, Max, Ack) ->
+    Node = build_list(L),
+    Min1 = minpos(node_min(Node), Min),
+    Max1 = max(node_max(Node), Max),
+    build_list_list(Ls, Min1, Max1, [Node | Ack]);
+build_list_list([], Min, Max, Ack) ->
+    {lists:reverse(Ack), Min, Max}.
+
+%% Reverting to an abstract syntax tree from the extended form.
+%% Note that the new comments are inserted after the original
+%% attributes are restored.
+
+revert_tree(Node) ->
+    case node_type(Node) of
+	leaf_node ->
+	    add_comments(Node, leaf_node_value(Node));
+	tree_node ->
+	    add_comments(Node,
+			 erl_syntax:set_attrs(
+			   erl_syntax:make_tree(
+			     tree_node_type(Node),
+			     revert_list(node_subtrees(Node))),
+			   tree_node_attrs(Node)));
+	list_node ->
+	    revert_list(node_subtrees(Node))
+    end.
+
+revert_list([T | Ts]) ->
+    [revert_tree(T) | revert_list(Ts)];
+revert_list([]) ->
+    [].
+
+add_comments(Node, Tree) ->
+    case node_precomments(Node) of
+	[] ->
+	    add_comments_1(Node, Tree);
+	Cs ->
+	    Cs1 = lists:reverse(expand_comments(Cs)),
+	    add_comments_1(Node,
+			   erl_syntax:add_precomments(Cs1, Tree))
+    end.
+
+add_comments_1(Node, Tree) ->
+    case node_postcomments(Node) of
+	[] ->
+	    Tree;
+	Cs ->
+	    Cs1 = lists:reverse(expand_comments(Cs)),
+	    erl_syntax:add_postcomments(Cs1, Tree)
+    end.
+
+expand_comments([C | Cs]) ->
+    [expand_comment(C) | expand_comments(Cs)];
+expand_comments([]) ->
+    [].
+
+expand_comment(C) ->
+    {L, _Col, Ind, Text} = C,
+    erl_syntax:set_pos(erl_syntax:comment(Ind, Text), L).
+
+
+%% =====================================================================
+%% Abstract data type for extended syntax trees.
+%%
+%% These explicitly distinguish between leaf and tree nodes, both
+%% corresponding to a single abstract syntax tree, and list nodes,
+%% corresponding to a left-to-right ordered sequence of such trees.
+%%
+%% All nodes have `min' and `max' fields, containing the first and last
+%% source lines, respectively, over which the tree extends.
+%%
+%% Tree nodes and list nodes have a `subtrees' field, containing the
+%% (extended) subtrees of the node. Tree nodes also have a `type' field,
+%% containing the atom returned by `erl_syntax:type' for the
+%% corresponding abstract syntax tree, and an `attrs' field, containing
+%% the value of `erl_syntax:get_attrs' for the abstract syntax tree.
+%%
+%% Leaf nodes and tree nodes also have `precomments' and `postcomments'
+%% fields. The comment fields are lists of comment structures (in
+%% top-down order); the representation of comments has no consequence to
+%% the tree representation.
+%%
+%% Leaf nodes, lastly, have a `value' field containing the abstract
+%% syntax tree for any such tree that can have no subtrees, i.e., such
+%% that `erl_syntax:is_leaf' yields `true'.
+
+-record(leaf, {min = 0,
+	       max = 0,
+	       precomments = [],
+	       postcomments = [],
+	       value}).
+
+-record(tree, {min = 0,
+	       max = 0,
+	       type,
+	       attrs,
+	       precomments = [],
+	       postcomments = [],
+	       subtrees = []}).
+
+-record(list, {min = 0,
+	       max = 0,
+	       subtrees = []}).
+
+leaf_node(Min, Max, Value) ->
+    #leaf{min = Min,
+	  max = Max,
+	  value = Value}.
+
+tree_node(Min, Max, Type, Attrs, Subtrees) ->
+    #tree{min = Min,
+	  max = Max,
+	  type = Type,
+	  attrs = Attrs,
+	  subtrees = Subtrees}.
+
+list_node(Min, Max, Subtrees) ->
+    #list{min = Min,
+	  max = Max,
+	  subtrees = Subtrees}.
+
+node_type(#leaf{}) ->
+    leaf_node;
+node_type(#tree{}) ->
+    tree_node;
+node_type(#list{}) ->
+    list_node.
+
+node_min(#leaf{min = Min}) ->
+    Min;
+node_min(#tree{min = Min}) ->
+    Min;
+node_min(#list{min = Min}) ->
+    Min.
+
+node_max(#leaf{max = Max}) ->
+    Max;
+node_max(#tree{max = Max}) ->
+    Max;
+node_max(#list{max = Max}) ->
+    Max.
+
+node_kill_range(Node) ->
+    case Node of
+	#leaf{} ->
+	    Node#leaf{min = -1, max = -1};
+	#tree{} ->
+	    Node#tree{min = -1, max = -1};
+	#list{} ->
+	    Node#list{min = -1, max = -1}
+    end.
+
+node_precomments(#leaf{precomments = Cs}) ->
+    Cs;
+node_precomments(#tree{precomments = Cs}) ->
+    Cs.
+
+node_add_precomment(C, Node) ->
+    case Node of
+	#leaf{} ->
+	    Node#leaf{precomments = [C | Node#leaf.precomments]};
+	#tree{} ->
+	    Node#tree{precomments = [C | Node#tree.precomments]}
+    end.
+
+node_postcomments(#leaf{postcomments = Cs}) ->
+    Cs;
+node_postcomments(#tree{postcomments = Cs}) ->
+    Cs.
+
+node_add_postcomment(C, Node) ->
+    case Node of
+	#leaf{} ->
+	    Node#leaf{postcomments =
+		      [C | Node#leaf.postcomments]};
+	#tree{} ->
+	    Node#tree{postcomments =
+		      [C | Node#tree.postcomments]}
+    end.
+
+node_subtrees(#tree{subtrees = Subtrees}) ->
+    Subtrees;
+node_subtrees(#list{subtrees = Subtrees}) ->
+    Subtrees.
+
+leaf_node_value(#leaf{value = Value}) ->
+    Value.
+
+tree_node_type(#tree{type = Type}) ->
+    Type.
+
+set_node_subtrees(Node, Subtrees) ->
+    case Node of
+	#tree{} ->
+	    Node#tree{subtrees = Subtrees};
+	#list{} ->
+	    Node#list{subtrees = Subtrees}
+    end.
+
+tree_node_attrs(#tree{attrs = Attrs}) ->
+    Attrs.
+
+
+%% =====================================================================
+%% General utility functions
+
+%% Just the generic "maximum" function
+
+max(X, Y) when X > Y -> X;
+max(_, Y) -> Y.
+
+%% Return the least positive integer of X and Y, or zero if none of them
+%% are positive. (This is necessary for computing minimum source line
+%% numbers, since zero (or negative) numbers may occur, but they
+%% represent the "undefined" line number.)
+
+minpos(X, Y) when X < Y ->
+    minpos1(X, Y);
+minpos(X, Y) ->
+    minpos1(Y, X).
+
+minpos1(X, Y) when X < 1 ->
+    minpos2(Y);
+minpos1(X, _) ->
+    X.
+
+minpos2(X) when X < 1 ->
+    0;
+minpos2(X) ->
+    X.
+
+get_line(Node) ->
+    case erl_syntax:get_pos(Node) of
+	L when is_integer(L) ->
+	    L;
+	{L, _} when is_integer(L) ->
+	    L;
+	{_, L} when is_integer(L) ->
+	    L;
+	{L, _, _} when is_integer(L) ->
+	    L;
+	{_, L, _} when is_integer(L) ->
+	    L;
+	Pos ->
+	    exit({bad_position, Pos})
+    end.
+
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/erl_syntax.erl b/lib/syntax_tools/src/erl_syntax.erl
new file mode 100644
index 0000000000..6ceb3ddcaf
--- /dev/null
+++ b/lib/syntax_tools/src/erl_syntax.erl
@@ -0,0 +1,6938 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1997-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Abstract Erlang syntax trees.
+%%
+%% This module defines an abstract data type for representing Erlang
+%% source code as syntax trees, in a way that is backwards compatible
+%% with the data structures created by the Erlang standard library
+%% parser module <code>erl_parse</code> (often referred to as "parse
+%% trees", which is a bit of a misnomer). This means that all
+%% <code>erl_parse</code> trees are valid abstract syntax trees, but the
+%% reverse is not true: abstract syntax trees can in general not be used
+%% as input to functions expecting an <code>erl_parse</code> tree.
+%% However, as long as an abstract syntax tree represents a correct
+%% Erlang program, the function <a
+%% href="#revert-1"><code>revert/1</code></a> should be able to
+%% transform it to the corresponding <code>erl_parse</code>
+%% representation.
+%%
+%% A recommended starting point for the first-time user is the
+%% documentation of the <a
+%% href="#type-syntaxTree"><code>syntaxTree()</code></a> data type, and
+%% the function <a href="#type-1"><code>type/1</code></a>.
+%%
+%% <h3><b>NOTES:</b></h3>
+%%
+%% This module deals with the composition and decomposition of
+%% <em>syntactic</em> entities (as opposed to semantic ones); its
+%% purpose is to hide all direct references to the data structures used
+%% to represent these entities. With few exceptions, the functions in
+%% this module perform no semantic interpretation of their inputs, and
+%% in general, the user is assumed to pass type-correct arguments - if
+%% this is not done, the effects are not defined.
+%%
+%% With the exception of the <code>erl_parse</code> data structures,
+%% the internal representations of abstract syntax trees are subject to
+%% change without notice, and should not be documented outside this
+%% module. Furthermore, we do not give any guarantees on how an abstract
+%% syntax tree may or may not be represented, <em>with the following
+%% exceptions</em>: no syntax tree is represented by a single atom, such
+%% as <code>none</code>, by a list constructor <code>[X | Y]</code>, or
+%% by the empty list <code>[]</code>. This can be relied on when writing
+%% functions that operate on syntax trees.
+
+%% @type syntaxTree(). An abstract syntax tree. The
+%% <code>erl_parse</code> "parse tree" representation is a subset of the
+%% <code>syntaxTree()</code> representation.
+%%
+%% Every abstract syntax tree node has a <em>type</em>, given by the
+%% function <a href="#type-1"><code>type/1</code></a>. Each node also
+%% has associated <em>attributes</em>; see <a
+%% href="#get_attrs-1"><code>get_attrs/1</code></a> for details. The
+%% functions <a href="#make_tree-2"><code>make_tree/2</code></a> and <a
+%% href="#subtrees-1"><code>subtrees/1</code></a> are generic
+%% constructor/decomposition functions for abstract syntax trees. The
+%% functions <a href="#abstract-1"><code>abstract/1</code></a> and <a
+%% href="#concrete-1"><code>concrete/1</code></a> convert between
+%% constant Erlang terms and their syntactic representations. The set of
+%% syntax tree nodes is extensible through the <a
+%% href="#tree-2"><code>tree/2</code></a> function.
+%%
+%% A syntax tree can be transformed to the <code>erl_parse</code>
+%% representation with the <a href="#revert-1"><code>revert/1</code></a>
+%% function.
+
+-module(erl_syntax).
+
+-export([type/1,
+	 is_leaf/1,
+	 is_form/1,
+	 is_literal/1,
+	 abstract/1,
+	 concrete/1,
+	 revert/1,
+	 revert_forms/1,
+	 subtrees/1,
+	 make_tree/2,
+	 update_tree/2,
+	 meta/1,
+
+	 get_pos/1,
+	 set_pos/2,
+	 copy_pos/2,
+	 get_precomments/1,
+	 set_precomments/2,
+	 add_precomments/2,
+	 get_postcomments/1,
+	 set_postcomments/2,
+	 add_postcomments/2,
+	 has_comments/1,
+	 remove_comments/1,
+	 copy_comments/2,
+	 join_comments/2,
+	 get_ann/1,
+	 set_ann/2,
+	 add_ann/2,
+	 copy_ann/2,
+	 get_attrs/1,
+	 set_attrs/2,
+	 copy_attrs/2,
+
+	 flatten_form_list/1,
+	 cons/2,
+	 list_head/1,
+	 list_tail/1,
+	 is_list_skeleton/1,
+	 is_proper_list/1,
+	 list_elements/1,
+	 list_length/1,
+	 normalize_list/1,
+	 compact_list/1,
+
+	 application/2,
+	 application/3,
+	 application_arguments/1,
+	 application_operator/1,
+	 arity_qualifier/2,
+	 arity_qualifier_argument/1,
+	 arity_qualifier_body/1,
+	 atom/1,
+	 is_atom/2,
+	 atom_value/1,
+	 atom_literal/1,
+	 atom_name/1,
+	 attribute/1,
+	 attribute/2,
+	 attribute_arguments/1,
+	 attribute_name/1,
+	 binary/1,
+	 binary_comp/2,
+	 binary_comp_template/1,
+	 binary_comp_body/1,
+	 binary_field/1,
+	 binary_field/2,
+	 binary_field/3,
+	 binary_field_body/1,
+	 binary_field_types/1,
+	 binary_field_size/1,
+	 binary_fields/1,
+	 binary_generator/2,
+	 binary_generator_body/1,
+	 binary_generator_pattern/1,
+	 block_expr/1,
+	 block_expr_body/1,
+	 case_expr/2,
+	 case_expr_argument/1,
+	 case_expr_clauses/1,
+	 catch_expr/1,
+	 catch_expr_body/1,
+	 char/1,
+	 is_char/2,
+	 char_value/1,
+	 char_literal/1,
+	 clause/2,
+	 clause/3,
+	 clause_body/1,
+	 clause_guard/1,
+	 clause_patterns/1,
+	 comment/1,
+	 comment/2,
+	 comment_padding/1,
+	 comment_text/1,
+	 cond_expr/1,
+	 cond_expr_clauses/1,
+	 conjunction/1,
+	 conjunction_body/1,
+	 disjunction/1,
+	 disjunction_body/1,
+	 eof_marker/0,
+	 error_marker/1,
+	 error_marker_info/1,
+	 float/1,
+	 float_value/1,
+	 float_literal/1,
+	 form_list/1,
+	 form_list_elements/1,
+	 fun_expr/1,
+	 fun_expr_arity/1,
+	 fun_expr_clauses/1,
+	 function/2,
+	 function_arity/1,
+	 function_clauses/1,
+	 function_name/1,
+	 generator/2,
+	 generator_body/1,
+	 generator_pattern/1,
+	 if_expr/1,
+	 if_expr_clauses/1,
+	 implicit_fun/1,
+	 implicit_fun/2,
+	 implicit_fun/3,
+	 implicit_fun_name/1,
+	 infix_expr/3,
+	 infix_expr_left/1,
+	 infix_expr_operator/1,
+	 infix_expr_right/1,
+	 integer/1,
+	 is_integer/2,
+	 integer_value/1,
+	 integer_literal/1,
+	 list/1,
+	 list/2,
+	 list_comp/2,
+	 list_comp_body/1,
+	 list_comp_template/1,
+	 list_prefix/1,
+	 list_suffix/1,
+	 macro/1,
+	 macro/2,
+	 macro_arguments/1,
+	 macro_name/1,
+	 match_expr/2,
+	 match_expr_body/1,
+	 match_expr_pattern/1,
+	 module_qualifier/2,
+	 module_qualifier_argument/1,
+	 module_qualifier_body/1,
+	 nil/0,
+	 operator/1,
+	 operator_literal/1,
+	 operator_name/1,
+	 parentheses/1,
+	 parentheses_body/1,
+	 prefix_expr/2,
+	 prefix_expr_argument/1,
+	 prefix_expr_operator/1,
+	 qualified_name/1,
+	 qualified_name_segments/1,
+	 query_expr/1,
+	 query_expr_body/1,
+	 receive_expr/1,
+	 receive_expr/3,
+	 receive_expr_action/1,
+	 receive_expr_clauses/1,
+	 receive_expr_timeout/1,
+	 record_access/2,
+	 record_access/3,
+	 record_access_argument/1,
+	 record_access_field/1,
+	 record_access_type/1,
+	 record_expr/2,
+	 record_expr/3,
+	 record_expr_argument/1,
+	 record_expr_fields/1,
+	 record_expr_type/1,
+	 record_field/1,
+	 record_field/2,
+	 record_field_name/1,
+	 record_field_value/1,
+	 record_index_expr/2,
+	 record_index_expr_field/1,
+	 record_index_expr_type/1,
+	 rule/2,
+	 rule_arity/1,
+	 rule_clauses/1,
+	 rule_name/1,
+	 size_qualifier/2,
+	 size_qualifier_argument/1,
+	 size_qualifier_body/1,
+	 string/1,
+	 is_string/2,
+	 string_value/1,
+	 string_literal/1,
+	 text/1,
+	 text_string/1,
+	 try_expr/2,
+	 try_expr/3,
+	 try_expr/4,
+	 try_after_expr/2,
+	 try_expr_body/1,
+	 try_expr_clauses/1,
+	 try_expr_handlers/1,
+	 try_expr_after/1,
+	 class_qualifier/2,
+	 class_qualifier_argument/1,
+	 class_qualifier_body/1,
+	 tuple/1,
+	 tuple_elements/1,
+	 tuple_size/1,
+	 underscore/0,
+	 variable/1,
+	 variable_name/1,
+	 variable_literal/1,
+	 warning_marker/1,
+	 warning_marker_info/1,
+
+	 tree/1,
+	 tree/2,
+	 data/1,
+	 is_tree/1]).
+
+
+%% =====================================================================
+%% IMPLEMENTATION NOTES:
+%%
+%% All nodes are represented by tuples of arity 2 or greater, whose
+%% first element is an atom which uniquely identifies the type of the
+%% node. (In the backwards-compatible representation, the interpretation
+%% is also often dependent on the context; the second element generally
+%% holds the position information - with a couple of exceptions; see
+%% `get_pos' and `set_pos' for details). In the documentation of this
+%% module, `Pos' is the source code position information associated with
+%% a node; usually, this is a positive integer indicating the original
+%% source code line, but no assumptions are made in this module
+%% regarding the format or interpretation of position information. When
+%% a syntax tree node is constructed, its associated position is by
+%% default set to the integer zero.
+%% =====================================================================
+
+-define(NO_UNUSED, true).
+
+%% =====================================================================
+%% Declarations of globally used internal data structures
+%% =====================================================================
+
+%% `com' records are used to hold comment information attached to a
+%% syntax tree node or a wrapper structure.
+%%
+%% #com{pre :: Pre, post :: Post}
+%%
+%%	Pre = Post = [Com]
+%%	Com = syntaxTree()
+%%
+%%	type(Com) = comment
+
+-record(com, {pre = [],
+	      post = []}).
+
+%% `attr' records store node attributes as an aggregate.
+%%
+%% #attr{pos :: Pos, ann :: Ann, com :: Comments}
+%%
+%%	Pos = term()
+%%	Ann = [term()]
+%%	Comments = none | #com{}
+%%
+%% where `Pos' `Ann' and `Comments' are the corresponding values of a
+%% `tree' or `wrapper' record.
+
+-record(attr, {pos = 0,
+	       ann = [],
+	       com = none}).
+
+%% `tree' records represent new-form syntax tree nodes.
+%%
+%% Tree = #tree{type :: Type, attr :: Attr, data :: Data}
+%%
+%%	Type = atom()
+%%	Attr = #attr{}
+%%	Data = term()
+%%
+%%	is_tree(Tree) = true
+
+-record(tree, {type,
+	       attr = #attr{} :: #attr{},
+	       data}).
+
+%% `wrapper' records are used for attaching new-form node information to
+%% `erl_parse' trees.
+%%
+%% Wrapper = #wrapper{type :: Type, attr :: Attr, tree :: ParseTree}
+%%
+%%	Type = atom()
+%%	Attr = #attr{}
+%%	ParseTree = term()
+%%
+%%	is_tree(Wrapper) = false
+
+-record(wrapper, {type,
+		  attr = #attr{} :: #attr{},
+		  tree}).
+
+
+%% =====================================================================
+%%
+%%			Exported functions
+%%
+%% =====================================================================
+
+
+%% =====================================================================
+%% @spec type(Node::syntaxTree()) -> atom()
+%%
+%% @doc Returns the type tag of <code>Node</code>. If <code>Node</code>
+%% does not represent a syntax tree, evaluation fails with reason
+%% <code>badarg</code>. Node types currently defined by this module are:
+%% <p><center><table border="1">
+%%  <tr>
+%%   <td>application</td>
+%%   <td>arity_qualifier</td>
+%%   <td>atom</td>
+%%   <td>attribute</td>
+%%  </tr><tr>
+%%   <td>binary</td>
+%%   <td>binary_field</td>
+%%   <td>block_expr</td>
+%%   <td>case_expr</td>
+%%  </tr><tr>
+%%   <td>catch_expr</td>
+%%   <td>char</td>
+%%   <td>class_qualifier</td>
+%%   <td>clause</td>
+%%  </tr><tr>
+%%   <td>comment</td>
+%%   <td>cond_expr</td>
+%%   <td>conjunction</td>
+%%   <td>disjunction</td>
+%%  </tr><tr>
+%%   <td>eof_marker</td>
+%%   <td>error_marker</td>
+%%   <td>float</td>
+%%   <td>form_list</td>
+%%  </tr><tr>
+%%   <td>fun_expr</td>
+%%   <td>function</td>
+%%   <td>generator</td>
+%%   <td>if_expr</td>
+%%  </tr><tr>
+%%   <td>implicit_fun</td>
+%%   <td>infix_expr</td>
+%%   <td>integer</td>
+%%   <td>list</td>
+%%  </tr><tr>
+%%   <td>list_comp</td>
+%%   <td>macro</td>
+%%   <td>match_expr</td>
+%%   <td>module_qualifier</td>
+%%  </tr><tr>
+%%   <td>nil</td>
+%%   <td>operator</td>
+%%   <td>parentheses</td>
+%%   <td>prefix_expr</td>
+%%  </tr><tr>
+%%   <td>qualified_name</td>
+%%   <td>query_expr</td>
+%%   <td>receive_expr</td>
+%%   <td>record_access</td>
+%%  </tr><tr>
+%%   <td>record_expr</td>
+%%   <td>record_field</td>
+%%   <td>record_index_expr</td>
+%%   <td>rule</td>
+%%  </tr><tr>
+%%   <td>size_qualifier</td>
+%%   <td>string</td>
+%%   <td>text</td>
+%%   <td>try_expr</td>
+%%  </tr><tr>
+%%   <td>tuple</td>
+%%   <td>underscore</td>
+%%   <td>variable</td>
+%%   <td>warning_marker</td>
+%%  </tr>
+%% </table></center></p>
+%% <p>The user may (for special purposes) create additional nodes
+%% with other type tags, using the <code>tree/2</code> function.</p>
+%%
+%% <p>Note: The primary constructor functions for a node type should
+%% always have the same name as the node type itself.</p>
+%%
+%% @see tree/2
+%% @see application/3
+%% @see arity_qualifier/2
+%% @see atom/1
+%% @see attribute/2
+%% @see binary/1
+%% @see binary_field/2
+%% @see block_expr/1
+%% @see case_expr/2
+%% @see catch_expr/1
+%% @see char/1
+%% @see class_qualifier/2
+%% @see clause/3
+%% @see comment/2
+%% @see cond_expr/1
+%% @see conjunction/1
+%% @see disjunction/1
+%% @see eof_marker/0
+%% @see error_marker/1
+%% @see float/1
+%% @see form_list/1
+%% @see fun_expr/1
+%% @see function/2
+%% @see generator/2
+%% @see if_expr/1
+%% @see implicit_fun/2
+%% @see infix_expr/3
+%% @see integer/1
+%% @see list/2
+%% @see list_comp/2
+%% @see macro/2
+%% @see match_expr/2
+%% @see module_qualifier/2
+%% @see nil/0
+%% @see operator/1
+%% @see parentheses/1
+%% @see prefix_expr/2
+%% @see qualified_name/1
+%% @see query_expr/1
+%% @see receive_expr/3
+%% @see record_access/3
+%% @see record_expr/2
+%% @see record_field/2
+%% @see record_index_expr/2
+%% @see rule/2
+%% @see size_qualifier/2
+%% @see string/1
+%% @see text/1
+%% @see try_expr/3
+%% @see tuple/1
+%% @see underscore/0
+%% @see variable/1
+%% @see warning_marker/1
+
+type(#tree{type = T}) ->
+    T;
+type(#wrapper{type = T}) ->
+    T;
+type(Node) ->
+    %% Check for `erl_parse'-compatible nodes, and otherwise fail.
+    case Node of
+	%% Leaf types
+	{atom, _, _} -> atom;
+	{char, _, _} -> char;
+	{float, _, _} -> float;
+	{integer, _, _} -> integer;
+	{nil, _} -> nil;
+	{string, _, _} -> string;
+	{var, _, Name} ->
+	    if Name =:= '_' -> underscore;
+	       true -> variable
+	    end;
+	{error, _} -> error_marker;
+	{warning, _} -> warning_marker;
+	{eof, _} -> eof_marker;
+
+	%% Composite types
+	{'case', _, _, _} -> case_expr;
+	{'catch', _, _} -> catch_expr;
+	{'cond', _, _} -> cond_expr;
+	{'fun', _, {clauses, _}} -> fun_expr;
+	{'fun', _, {function, _, _}} -> implicit_fun;
+	{'fun', _, {function, _, _, _}} -> implicit_fun;
+	{'if', _, _} -> if_expr;
+	{'receive', _, _, _, _} -> receive_expr;
+	{'receive', _, _} -> receive_expr;
+	{attribute, _, _, _} -> attribute;
+	{bin, _, _} -> binary;
+	{bin_element, _, _, _, _} -> binary_field;
+	{block, _, _} -> block_expr;
+	{call, _, _, _} -> application;
+	{clause, _, _, _, _} -> clause;
+	{cons, _, _, _} -> list;
+	{function, _, _, _, _} -> function;
+	{b_generate, _, _, _} -> binary_generator;
+	{generate, _, _, _} -> generator;
+	{lc, _, _, _} -> list_comp;
+	{bc, _, _, _} -> binary_comp;		
+	{match, _, _, _} -> match_expr;
+	{op, _, _, _, _} -> infix_expr;
+	{op, _, _, _} -> prefix_expr;
+	{'query', _, _} -> query_expr;
+	{record, _, _, _, _} -> record_expr;
+	{record, _, _, _} -> record_expr;
+	{record_field, _, _, _, _} -> record_access;
+	{record_field, _, _, _} ->
+	    case is_qualified_name(Node) of
+		true -> qualified_name;
+		false -> record_access
+	    end;
+	{record_index, _, _, _} -> record_index_expr;
+	{remote, _, _, _} -> module_qualifier;
+	{rule, _, _, _, _} -> rule;
+	{'try', _, _, _, _, _} -> try_expr;
+	{tuple, _, _} -> tuple;
+	_ ->
+	    erlang:error({badarg, Node})
+    end.
+
+
+%% =====================================================================
+%% @spec is_leaf(Node::syntaxTree()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> is a leaf node,
+%% otherwise <code>false</code>. The currently recognised leaf node
+%% types are:
+%% <p><center><table border="1">
+%%  <tr>
+%%   <td><code>atom</code></td>
+%%   <td><code>char</code></td>
+%%   <td><code>comment</code></td>
+%%   <td><code>eof_marker</code></td>
+%%   <td><code>error_marker</code></td>
+%%  </tr><tr>
+%%   <td><code>float</code></td>
+%%   <td><code>integer</code></td>
+%%   <td><code>nil</code></td>
+%%   <td><code>operator</code></td>
+%%   <td><code>string</code></td>
+%%  </tr><tr>
+%%   <td><code>text</code></td>
+%%   <td><code>underscore</code></td>
+%%   <td><code>variable</code></td>
+%%   <td><code>warning_marker</code></td>
+%%  </tr>
+%% </table></center></p>
+%% <p>A node of type <code>tuple</code> is a leaf node if and only if
+%% its arity is zero.</p>
+%%
+%% <p>Note: not all literals are leaf nodes, and vice versa. E.g.,
+%% tuples with nonzero arity and nonempty lists may be literals, but are
+%% not leaf nodes. Variables, on the other hand, are leaf nodes but not
+%% literals.</p>
+%% 
+%% @see type/1
+%% @see is_literal/1
+
+is_leaf(Node) ->
+    case type(Node) of
+	atom -> true;
+	char -> true;
+	comment -> true;	% nonstandard type
+	eof_marker -> true;
+	error_marker -> true;
+	float -> true;
+	integer -> true;
+	nil -> true;
+	operator -> true;	% nonstandard type
+	string -> true;
+	text -> true;		% nonstandard type
+	tuple -> tuple_elements(Node) =:= [];
+	underscore -> true;
+	variable -> true;
+	warning_marker -> true;
+	_ -> false
+    end.
+
+
+%% =====================================================================
+%% @spec is_form(Node::syntaxTree()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> is a syntax tree
+%% representing a so-called "source code form", otherwise
+%% <code>false</code>. Forms are the Erlang source code units which,
+%% placed in sequence, constitute an Erlang program. Current form types
+%% are:
+%% <p><center><table border="1">
+%%  <tr>
+%%   <td><code>attribute</code></td>
+%%   <td><code>comment</code></td>
+%%   <td><code>error_marker</code></td>
+%%   <td><code>eof_marker</code></td>
+%%   <td><code>form_list</code></td>
+%%  </tr><tr>
+%%   <td><code>function</code></td>
+%%   <td><code>rule</code></td>
+%%   <td><code>warning_marker</code></td>
+%%   <td><code>text</code></td>
+%%  </tr>
+%% </table></center></p>
+%% @see type/1
+%% @see attribute/2 
+%% @see comment/2
+%% @see eof_marker/0
+%% @see error_marker/1
+%% @see form_list/1
+%% @see function/2
+%% @see rule/2
+%% @see warning_marker/1
+
+is_form(Node) ->
+    case type(Node) of
+	attribute -> true;
+	comment -> true;
+	function -> true;
+	eof_marker -> true;
+	error_marker -> true;
+	form_list -> true;
+	rule -> true;
+	warning_marker -> true;
+	text -> true;
+	_ -> false
+    end.
+
+
+%% =====================================================================
+%% @spec get_pos(Node::syntaxTree()) -> term()
+%%
+%% @doc Returns the position information associated with
+%% <code>Node</code>. This is usually a nonnegative integer (indicating
+%% the source code line number), but may be any term. By default, all
+%% new tree nodes have their associated position information set to the
+%% integer zero.
+%%
+%% @see set_pos/2
+%% @see get_attrs/1
+
+%% All `erl_parse' tree nodes are represented by tuples whose second
+%% field is the position information (usually an integer), *with the
+%% exceptions of* `{error, ...}' (type `error_marker') and `{warning,
+%% ...}' (type `warning_marker'), which only contain the associated line
+%% number *of the error descriptor*; this is all handled transparently
+%% by `get_pos' and `set_pos'.
+
+get_pos(#tree{attr = Attr}) ->
+    Attr#attr.pos;
+get_pos(#wrapper{attr = Attr}) ->
+    Attr#attr.pos;
+get_pos({error, {Pos, _, _}}) ->
+    Pos;
+get_pos({warning, {Pos, _, _}}) ->
+    Pos;
+get_pos(Node) ->
+    %% Here, we assume that we have an `erl_parse' node with position
+    %% information in element 2.
+    element(2, Node).
+
+
+%% =====================================================================
+%% @spec set_pos(Node::syntaxTree(), Pos::term()) -> syntaxTree()
+%%
+%% @doc Sets the position information of <code>Node</code> to
+%% <code>Pos</code>.
+%%
+%% @see get_pos/1
+%% @see copy_pos/2
+
+set_pos(Node, Pos) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = Attr#attr{pos = Pos}};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = Attr#attr{pos = Pos}};
+	_ ->
+	    %% We then assume we have an `erl_parse' node, and create a
+	    %% wrapper around it to make things more uniform.
+	    set_pos(wrap(Node), Pos)
+    end.
+
+
+%% =====================================================================
+%% @spec copy_pos(Source::syntaxTree(), Target::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Copies the position information from <code>Source</code> to
+%% <code>Target</code>.
+%%
+%% <p>This is equivalent to <code>set_pos(Target,
+%% get_pos(Source))</code>, but potentially more efficient.</p>
+%%
+%% @see get_pos/1
+%% @see set_pos/2
+
+copy_pos(Source, Target) ->
+    set_pos(Target, get_pos(Source)).
+
+
+%% =====================================================================
+%% `get_com' and `set_com' are for internal use only.
+
+get_com(#tree{attr = Attr}) -> Attr#attr.com;
+get_com(#wrapper{attr = Attr}) -> Attr#attr.com;
+get_com(_) -> none.
+
+set_com(Node, Com) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = Attr#attr{com = Com}};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = Attr#attr{com = Com}};
+	_ ->
+	    set_com(wrap(Node), Com)
+    end.
+
+
+%% =====================================================================
+%% @spec get_precomments(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the associated pre-comments of a node. This is a
+%% possibly empty list of abstract comments, in top-down textual order.
+%% When the code is formatted, pre-comments are typically displayed
+%% directly above the node. For example:
+%% <pre>
+%%         % Pre-comment of function
+%%         foo(X) -> {bar, X}.</pre>
+%%
+%% <p>If possible, the comment should be moved before any preceding
+%% separator characters on the same line. E.g.:
+%% <pre>
+%%         foo([X | Xs]) ->
+%%             % Pre-comment of 'bar(X)' node
+%%             [bar(X) | foo(Xs)];
+%%         ...</pre>
+%% (where the comment is moved before the "<code>[</code>").</p>
+%%
+%% @see comment/2
+%% @see set_precomments/2
+%% @see get_postcomments/1
+%% @see get_attrs/1
+
+get_precomments(#tree{attr = Attr}) -> get_precomments_1(Attr);
+get_precomments(#wrapper{attr = Attr}) -> get_precomments_1(Attr);
+get_precomments(_) -> [].
+
+get_precomments_1(#attr{com = none}) -> [];
+get_precomments_1(#attr{com = #com{pre = Cs}}) -> Cs.
+
+
+%% =====================================================================
+%% @spec set_precomments(Node::syntaxTree(),
+%%                       Comments::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Sets the pre-comments of <code>Node</code> to
+%% <code>Comments</code>. <code>Comments</code> should be a possibly
+%% empty list of abstract comments, in top-down textual order.
+%%
+%% @see comment/2
+%% @see get_precomments/1
+%% @see add_precomments/2
+%% @see set_postcomments/2
+%% @see copy_comments/2
+%% @see remove_comments/1
+%% @see join_comments/2
+
+set_precomments(Node, Cs) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = set_precomments_1(Attr, Cs)};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = set_precomments_1(Attr, Cs)};
+	_ ->
+	    set_precomments(wrap(Node), Cs)
+    end.
+
+set_precomments_1(#attr{com = none} = Attr, Cs) ->
+    Attr#attr{com = #com{pre = Cs}};
+set_precomments_1(#attr{com = Com} = Attr, Cs) ->
+    Attr#attr{com = Com#com{pre = Cs}}.
+
+
+%% =====================================================================
+%% @spec add_precomments(Comments::[syntaxTree()],
+%%                       Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Appends <code>Comments</code> to the pre-comments of
+%% <code>Node</code>.
+%%
+%% <p>Note: This is equivalent to <code>set_precomments(Node,
+%% get_precomments(Node) ++ Comments)</code>, but potentially more
+%% efficient.</p>
+%%
+%% @see comment/2
+%% @see get_precomments/1
+%% @see set_precomments/2
+%% @see add_postcomments/2
+%% @see join_comments/2
+
+add_precomments(Cs, Node) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = add_precomments_1(Cs, Attr)};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = add_precomments_1(Cs, Attr)};
+	_ ->
+	    add_precomments(Cs, wrap(Node))
+    end.
+
+add_precomments_1(Cs, #attr{com = none} = Attr) ->
+    Attr#attr{com = #com{pre = Cs}};
+add_precomments_1(Cs, #attr{com = Com} = Attr) ->
+    Attr#attr{com = Com#com{pre = Com#com.pre ++ Cs}}.
+
+
+%% =====================================================================
+%% @spec get_postcomments(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the associated post-comments of a node. This is a
+%% possibly empty list of abstract comments, in top-down textual order.
+%% When the code is formatted, post-comments are typically displayed to
+%% the right of and/or below the node. For example:
+%% <pre>
+%%         {foo, X, Y}     % Post-comment of tuple</pre>
+%%
+%% <p>If possible, the comment should be moved past any following
+%% separator characters on the same line, rather than placing the
+%% separators on the following line. E.g.:
+%% <pre>
+%%         foo([X | Xs], Y) ->
+%%             foo(Xs, bar(X));     % Post-comment of 'bar(X)' node
+%%          ...</pre>
+%% (where the comment is moved past the rightmost "<code>)</code>" and
+%% the "<code>;</code>").</p>
+%%
+%% @see comment/2
+%% @see set_postcomments/2
+%% @see get_precomments/1
+%% @see get_attrs/1
+
+get_postcomments(#tree{attr = Attr}) -> get_postcomments_1(Attr);
+get_postcomments(#wrapper{attr = Attr}) -> get_postcomments_1(Attr);
+get_postcomments(_) -> [].
+
+get_postcomments_1(#attr{com = none}) -> [];
+get_postcomments_1(#attr{com = #com{post = Cs}}) -> Cs.
+
+
+%% =====================================================================
+%% @spec set_postcomments(Node::syntaxTree(),
+%%                        Comments::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Sets the post-comments of <code>Node</code> to
+%% <code>Comments</code>. <code>Comments</code> should be a possibly
+%% empty list of abstract comments, in top-down textual order
+%%
+%% @see comment/2
+%% @see get_postcomments/1
+%% @see add_postcomments/2
+%% @see set_precomments/2
+%% @see copy_comments/2
+%% @see remove_comments/1
+%% @see join_comments/2
+
+set_postcomments(Node, Cs) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = set_postcomments_1(Attr, Cs)};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = set_postcomments_1(Attr, Cs)};
+	_ ->
+	    set_postcomments(wrap(Node), Cs)
+    end.
+
+set_postcomments_1(#attr{com = none} = Attr, Cs) ->
+    Attr#attr{com = #com{post = Cs}};
+set_postcomments_1(#attr{com = Com} = Attr, Cs) ->
+    Attr#attr{com = Com#com{post = Cs}}.
+
+
+%% =====================================================================
+%% @spec add_postcomments(Comments::[syntaxTree()],
+%%                        Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Appends <code>Comments</code> to the post-comments of
+%% <code>Node</code>.
+%%
+%% <p>Note: This is equivalent to <code>set_postcomments(Node,
+%% get_postcomments(Node) ++ Comments)</code>, but potentially more
+%% efficient.</p>
+%%
+%% @see comment/2
+%% @see get_postcomments/1
+%% @see set_postcomments/2
+%% @see add_precomments/2
+%% @see join_comments/2
+
+add_postcomments(Cs, Node) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = add_postcomments_1(Cs, Attr)};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = add_postcomments_1(Cs, Attr)};
+	_ ->
+	    add_postcomments(Cs, wrap(Node))
+    end.
+
+add_postcomments_1(Cs, #attr{com = none} = Attr) ->
+    Attr#attr{com = #com{post = Cs}};
+add_postcomments_1(Cs, #attr{com = Com} = Attr) ->
+    Attr#attr{com = Com#com{post = Com#com.post ++ Cs}}.
+
+
+%% =====================================================================
+%% @spec has_comments(Node::syntaxTree()) -> bool()
+%%
+%% @doc Yields <code>false</code> if the node has no associated
+%% comments, and <code>true</code> otherwise.
+%%
+%% <p>Note: This is equivalent to <code>(get_precomments(Node) == [])
+%% and (get_postcomments(Node) == [])</code>, but potentially more
+%% efficient.</p>
+%%
+%% @see get_precomments/1
+%% @see get_postcomments/1
+%% @see remove_comments/1
+
+has_comments(#tree{attr = Attr}) ->
+    case Attr#attr.com of
+	none -> false;
+	#com{pre = [], post = []} -> false;
+	_ -> true
+    end;
+has_comments(#wrapper{attr = Attr}) ->
+    case Attr#attr.com of
+	none -> false;
+	#com{pre = [], post = []} -> false;
+	_ -> true
+    end;
+has_comments(_) -> false.
+
+
+%% =====================================================================
+%% @spec remove_comments(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Clears the associated comments of <code>Node</code>.
+%%
+%% <p>Note: This is equivalent to
+%% <code>set_precomments(set_postcomments(Node, []), [])</code>, but
+%% potentially more efficient.</p>
+%%
+%% @see set_precomments/2
+%% @see set_postcomments/2
+
+remove_comments(Node) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = Attr#attr{com = none}};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = Attr#attr{com = none}};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec copy_comments(Source::syntaxTree(), Target::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Copies the pre- and postcomments from <code>Source</code> to
+%% <code>Target</code>.
+%%
+%% <p>Note: This is equivalent to
+%% <code>set_postcomments(set_precomments(Target,
+%% get_precomments(Source)), get_postcomments(Source))</code>, but
+%% potentially more efficient.</p>
+%%
+%% @see comment/2
+%% @see get_precomments/1
+%% @see get_postcomments/1
+%% @see set_precomments/2
+%% @see set_postcomments/2
+
+copy_comments(Source, Target) ->
+    set_com(Target, get_com(Source)).
+
+
+%% =====================================================================
+%% @spec join_comments(Source::syntaxTree(), Target::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Appends the comments of <code>Source</code> to the current
+%% comments of <code>Target</code>.
+%%
+%% <p>Note: This is equivalent to
+%% <code>add_postcomments(get_postcomments(Source),
+%% add_precomments(get_precomments(Source), Target))</code>, but
+%% potentially more efficient.</p>
+%%
+%% @see comment/2
+%% @see get_precomments/1
+%% @see get_postcomments/1
+%% @see add_precomments/2
+%% @see add_postcomments/2
+
+join_comments(Source, Target) ->
+    add_postcomments(
+      get_postcomments(Source),
+      add_precomments(get_precomments(Source), Target)).
+
+
+%% =====================================================================
+%% @spec get_ann(syntaxTree()) -> [term()]
+%%
+%% @doc Returns the list of user annotations associated with a syntax
+%% tree node. For a newly created node, this is the empty list. The
+%% annotations may be any terms.
+%%
+%% @see set_ann/2
+%% @see get_attrs/1
+
+get_ann(#tree{attr = Attr}) -> Attr#attr.ann;
+get_ann(#wrapper{attr = Attr}) -> Attr#attr.ann;
+get_ann(_) -> [].
+
+
+%% =====================================================================
+%% @spec set_ann(Node::syntaxTree(), Annotations::[term()]) ->
+%%           syntaxTree()
+%%
+%% @doc Sets the list of user annotations of <code>Node</code> to
+%% <code>Annotations</code>.
+%%
+%% @see get_ann/1
+%% @see add_ann/2
+%% @see copy_ann/2
+
+set_ann(Node, As) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = Attr#attr{ann = As}};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = Attr#attr{ann = As}};
+	_ ->
+	    %% Assume we have an `erl_parse' node and create a wrapper
+	    %% structure to carry the annotation.
+	    set_ann(wrap(Node), As)
+    end.
+
+
+%% =====================================================================
+%% @spec add_ann(Annotation::term(), Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Appends the term <code>Annotation</code> to the list of user
+%% annotations of <code>Node</code>.
+%%
+%% <p>Note: this is equivalent to <code>set_ann(Node, [Annotation |
+%% get_ann(Node)])</code>, but potentially more efficient.</p>
+%%
+%% @see get_ann/1
+%% @see set_ann/2
+
+add_ann(A, Node) ->
+    case Node of
+	#tree{attr = Attr} ->
+	    Node#tree{attr = Attr#attr{ann = [A | Attr#attr.ann]}};
+	#wrapper{attr = Attr} ->
+	    Node#wrapper{attr = Attr#attr{ann = [A | Attr#attr.ann]}};
+	_ ->
+	    %% Assume we have an `erl_parse' node and create a wrapper
+	    %% structure to carry the annotation.
+	    add_ann(A, wrap(Node))
+    end.
+
+
+%% =====================================================================
+%% @spec copy_ann(Source::syntaxTree(), Target::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Copies the list of user annotations from <code>Source</code> to
+%% <code>Target</code>.
+%%
+%% <p>Note: this is equivalent to <code>set_ann(Target,
+%% get_ann(Source))</code>, but potentially more efficient.</p>
+%%
+%% @see get_ann/1
+%% @see set_ann/2
+
+copy_ann(Source, Target) ->
+    set_ann(Target, get_ann(Source)).
+
+
+%% =====================================================================
+%% @spec get_attrs(syntaxTree()) -> syntaxTreeAttributes()
+%%
+%% @doc Returns a representation of the attributes associated with a
+%% syntax tree node. The attributes are all the extra information that
+%% can be attached to a node. Currently, this includes position
+%% information, source code comments, and user annotations. The result
+%% of this function cannot be inspected directly; only attached to
+%% another node (cf. <code>set_attrs/2</code>).
+%%
+%% <p>For accessing individual attributes, see <code>get_pos/1</code>,
+%% <code>get_ann/1</code>, <code>get_precomments/1</code> and
+%% <code>get_postcomments/1</code>.</p>
+%%
+%% @type syntaxTreeAttributes(). This is an abstract representation of
+%% syntax tree node attributes; see the function <a
+%% href="#get_attrs-1"><code>get_attrs/1</code></a>.
+%% 
+%% @see set_attrs/2
+%% @see get_pos/1
+%% @see get_ann/1
+%% @see get_precomments/1
+%% @see get_postcomments/1
+
+get_attrs(#tree{attr = Attr}) -> Attr;
+get_attrs(#wrapper{attr = Attr}) -> Attr;
+get_attrs(Node) -> #attr{pos = get_pos(Node),
+			 ann = get_ann(Node),
+			 com = get_com(Node)}.
+
+
+%% =====================================================================
+%% @spec set_attrs(Node::syntaxTree(),
+%%                 Attributes::syntaxTreeAttributes()) -> syntaxTree()
+%%
+%% @doc Sets the attributes of <code>Node</code> to
+%% <code>Attributes</code>.
+%%
+%% @see get_attrs/1
+%% @see copy_attrs/2
+
+set_attrs(Node, Attr) ->
+    case Node of
+	#tree{} ->
+	    Node#tree{attr = Attr};
+	#wrapper{} ->
+	    Node#wrapper{attr = Attr};
+	_ ->
+	    set_attrs(wrap(Node), Attr)
+    end.
+
+
+%% =====================================================================
+%% @spec copy_attrs(Source::syntaxTree(), Target::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Copies the attributes from <code>Source</code> to
+%% <code>Target</code>.
+%%
+%% <p>Note: this is equivalent to <code>set_attrs(Target,
+%% get_attrs(Source))</code>, but potentially more efficient.</p>
+%%
+%% @see get_attrs/1
+%% @see set_attrs/2
+
+copy_attrs(S, T) ->
+    set_attrs(T, get_attrs(S)).
+
+
+%% =====================================================================
+%% @spec comment(Strings) -> syntaxTree()
+%% @equiv comment(none, Strings)
+
+comment(Strings) ->
+    comment(none, Strings).
+
+
+%% =====================================================================
+%% @spec comment(Padding, Strings::[string()]) -> syntaxTree()
+%%	    Padding = none | integer()
+%%
+%% @doc Creates an abstract comment with the given padding and text. If
+%% <code>Strings</code> is a (possibly empty) list
+%% <code>["<em>Txt1</em>", ..., "<em>TxtN</em>"]</code>, the result
+%% represents the source code text
+%% <pre>
+%%     %<em>Txt1</em>
+%%     ...
+%%     %<em>TxtN</em></pre>
+%% <code>Padding</code> states the number of empty character positions
+%% to the left of the comment separating it horizontally from
+%% source code on the same line (if any). If <code>Padding</code> is
+%% <code>none</code>, a default positive number is used. If
+%% <code>Padding</code> is an integer less than 1, there should be no
+%% separating space. Comments are in themselves regarded as source
+%% program forms.
+%%
+%% @see comment/1
+%% @see is_form/1
+
+-record(comment, {pad, text}).
+
+%% type(Node) = comment
+%% data(Node) = #comment{pad :: Padding, text :: Strings}
+%%
+%%	Padding = none | integer()
+%%	Strings = [string()]
+
+comment(Pad, Strings) ->
+    tree(comment, #comment{pad = Pad, text = Strings}).
+
+
+%% =====================================================================
+%% @spec comment_text(syntaxTree()) -> [string()]
+%%
+%% @doc Returns the lines of text of the abstract comment.
+%%
+%% @see comment/2
+
+comment_text(Node) ->
+    (data(Node))#comment.text.
+
+
+%% =====================================================================
+%% @spec comment_padding(syntaxTree()) -> none | integer()
+%%
+%% @doc Returns the amount of padding before the comment, or
+%% <code>none</code>. The latter means that a default padding may be
+%% used.
+%%
+%% @see comment/2
+
+comment_padding(Node) ->
+    (data(Node))#comment.pad.
+
+
+%% =====================================================================
+%% @spec form_list(Forms::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract sequence of "source code forms". If
+%% <code>Forms</code> is <code>[F1, ..., Fn]</code>, where each
+%% <code>Fi</code> is a form (cf. <code>is_form/1</code>, the result
+%% represents
+%% <pre>
+%%     <em>F1</em>
+%%     ...
+%%     <em>Fn</em></pre>
+%% where the <code>Fi</code> are separated by one or more line breaks. A
+%% node of type <code>form_list</code> is itself regarded as a source
+%% code form; cf. <code>flatten_form_list/1</code>.
+%%
+%% <p>Note: this is simply a way of grouping source code forms as a
+%% single syntax tree, usually in order to form an Erlang module
+%% definition.</p>
+%%
+%% @see form_list_elements/1
+%% @see is_form/1
+%% @see flatten_form_list/1
+
+%% type(Node) = form_list
+%% data(Node) = [Form]
+%%
+%%	Form = syntaxTree()
+%%	is_form(Form) = true
+
+form_list(Forms) ->
+    tree(form_list, Forms).
+
+
+%% =====================================================================
+%% @spec form_list_elements(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of subnodes of a <code>form_list</code> node.
+%%
+%% @see form_list/1
+
+form_list_elements(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec flatten_form_list(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Flattens sublists of a <code>form_list</code> node. Returns
+%% <code>Node</code> with all subtrees of type <code>form_list</code>
+%% recursively expanded, yielding a single "flat" abstract form
+%% sequence.
+%%
+%% @see form_list/1
+
+flatten_form_list(Node) ->
+    Fs = form_list_elements(Node),
+    Fs1 = lists:reverse(flatten_form_list_1(Fs, [])),
+    copy_attrs(Node, form_list(Fs1)).
+
+flatten_form_list_1([F | Fs], As) ->
+    case type(F) of
+	form_list ->
+	    As1 = flatten_form_list_1(form_list_elements(F), As),
+	    flatten_form_list_1(Fs, As1);
+	_ ->
+	    flatten_form_list_1(Fs, [F | As])
+    end;
+flatten_form_list_1([], As) ->
+    As.
+
+
+%% =====================================================================
+%% @spec text(String::string()) -> syntaxTree()
+%%
+%% @doc Creates an abstract piece of source code text. The result
+%% represents exactly the sequence of characters in <code>String</code>.
+%% This is useful in cases when one wants full control of the resulting
+%% output, e.g., for the appearance of floating-point numbers or macro
+%% definitions.
+%%
+%% @see text_string/1
+
+%% type(Node) = text
+%% data(Node) = string()
+
+text(String) ->
+    tree(text, String).
+
+
+%% =====================================================================
+%% @spec text_string(syntaxTree()) -> string()
+%%
+%% @doc Returns the character sequence represented by a
+%% <code>text</code> node.
+%%
+%% @see text/1
+
+text_string(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec variable(Name) -> syntaxTree()
+%%	    Name = atom() | string()
+%%
+%% @doc Creates an abstract variable with the given name.
+%% <code>Name</code> may be any atom or string that represents a
+%% lexically valid variable name, but <em>not</em> a single underscore
+%% character; cf. <code>underscore/0</code>.
+%%
+%% <p>Note: no checking is done whether the character sequence
+%% represents a proper variable name, i.e., whether or not its first
+%% character is an uppercase Erlang character, or whether it does not
+%% contain control characters, whitespace, etc.</p>
+%%
+%% @see variable_name/1
+%% @see variable_literal/1
+%% @see underscore/0
+
+%% type(Node) = variable
+%% data(Node) = atom()
+%%
+%% `erl_parse' representation:
+%%
+%% {var, Pos, Name}
+%%
+%%	Name = atom() \ '_'
+
+variable(Name) when is_atom(Name) ->
+    tree(variable, Name);
+variable(Name) ->
+    tree(variable, list_to_atom(Name)).
+
+revert_variable(Node) ->
+    Pos = get_pos(Node),
+    Name = variable_name(Node),
+    {var, Pos, Name}.
+
+
+%% =====================================================================
+%% @spec variable_name(syntaxTree()) -> atom()
+%%
+%% @doc Returns the name of a <code>variable</code> node as an atom.
+%%
+%% @see variable/1
+
+variable_name(Node) ->
+    case unwrap(Node) of
+	{var, _, Name} ->
+	    Name;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec variable_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the name of a <code>variable</code> node as a string.
+%%
+%% @see variable/1
+
+variable_literal(Node) ->
+    case unwrap(Node) of
+	{var, _, Name} ->
+	    atom_to_list(Name);
+	Node1 ->
+	    atom_to_list(data(Node1))
+    end.
+
+
+%% =====================================================================
+%% @spec underscore() -> syntaxTree()
+%%
+%% @doc Creates an abstract universal pattern ("<code>_</code>"). The
+%% lexical representation is a single underscore character. Note that
+%% this is <em>not</em> a variable, lexically speaking.
+%%
+%% @see variable/1
+
+%% type(Node) = underscore
+%% data(Node) = []
+%%
+%% `erl_parse' representation:
+%%
+%% {var, Pos, '_'}
+
+underscore() ->
+    tree(underscore, []).
+
+revert_underscore(Node) ->
+    Pos = get_pos(Node),
+    {var, Pos, '_'}.
+
+
+%% =====================================================================
+%% @spec integer(Value::integer()) -> syntaxTree()
+%%
+%% @doc Creates an abstract integer literal. The lexical representation
+%% is the canonical decimal numeral of <code>Value</code>.
+%%
+%% @see integer_value/1
+%% @see integer_literal/1
+%% @see is_integer/2
+
+%% type(Node) = integer
+%% data(Node) = integer()
+%%
+%% `erl_parse' representation:
+%%
+%% {integer, Pos, Value}
+%%
+%%	Value = integer()
+
+integer(Value) ->
+    tree(integer, Value).
+
+revert_integer(Node) ->
+    Pos = get_pos(Node),
+    {integer, Pos, integer_value(Node)}.
+
+
+%% =====================================================================
+%% @spec is_integer(Node::syntaxTree(), Value::integer()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> has type
+%% <code>integer</code> and represents <code>Value</code>, otherwise
+%% <code>false</code>.
+%%
+%% @see integer/1
+
+is_integer(Node, Value) ->
+    case unwrap(Node) of
+	{integer, _, Value} ->
+	    true;
+	#tree{type = integer, data = Value} ->
+	    true;
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec integer_value(syntaxTree()) -> integer()
+%%
+%% @doc Returns the value represented by an <code>integer</code> node.
+%%
+%% @see integer/1
+
+integer_value(Node) ->
+    case unwrap(Node) of
+	{integer, _, Value} ->
+	    Value;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec integer_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the numeral string represented by an
+%% <code>integer</code> node.
+%%
+%% @see integer/1
+
+integer_literal(Node) ->
+    integer_to_list(integer_value(Node)).
+
+
+%% =====================================================================
+%% @spec float(Value::float()) -> syntaxTree()
+%%
+%% @doc Creates an abstract floating-point literal. The lexical
+%% representation is the decimal floating-point numeral of
+%% <code>Value</code>.
+%%
+%% @see float_value/1
+%% @see float_literal/1
+
+%% type(Node) = float
+%% data(Node) = Value
+%%
+%%	Value = float()
+%%
+%% `erl_parse' representation:
+%%
+%% {float, Pos, Value}
+%%
+%%	Value = float()
+
+%% Note that under current versions of Erlang, the name `float/1' cannot
+%% be used for local calls (i.e., within the module) - it will be
+%% overridden by the type conversion BIF of the same name, so always use
+%% `make_float/1' for local calls.
+
+float(Value) ->
+    make_float(Value).
+
+make_float(Value) ->
+    tree(float, Value).
+
+revert_float(Node) ->
+    Pos = get_pos(Node),
+    {float, Pos, float_value(Node)}.
+
+
+%% =====================================================================
+%% @spec float_value(syntaxTree()) -> float()
+%%
+%% @doc Returns the value represented by a <code>float</code> node. Note
+%% that floating-point values should usually not be compared for
+%% equality.
+%%
+%% @see float/1
+
+float_value(Node) ->
+    case unwrap(Node) of
+	{float, _, Value} ->
+	    Value;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec float_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the numeral string represented by a <code>float</code>
+%% node.
+%%
+%% @see float/1
+
+float_literal(Node) ->
+    float_to_list(float_value(Node)).
+
+
+%% =====================================================================
+%% @spec char(Value::char()) -> syntaxTree()
+%%
+%% @doc Creates an abstract character literal. The result represents
+%% "<code>$<em>Name</em></code>", where <code>Name</code> corresponds to
+%% <code>Value</code>.
+%%
+%% <p>Note: the literal corresponding to a particular character value is
+%% not uniquely defined. E.g., the character "<code>a</code>" can be
+%% written both as "<code>$a</code>" and "<code>$\141</code>", and a Tab
+%% character can be written as "<code>$\11</code>", "<code>$\011</code>"
+%% or "<code>$\t</code>".</p>
+%%
+%% @see char_value/1
+%% @see char_literal/1
+%% @see is_char/2
+
+%% type(Node) = char
+%% data(Node) = char()
+%%
+%% `erl_parse' representation:
+%%
+%% {char, Pos, Code}
+%%
+%%	Code = integer()
+
+char(Char) ->
+    tree(char, Char).
+
+revert_char(Node) ->
+    Pos = get_pos(Node),
+    {char, Pos, char_value(Node)}.
+
+
+%% =====================================================================
+%% @spec is_char(Node::syntaxTree(), Value::char()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> has type
+%% <code>char</code> and represents <code>Value</code>, otherwise
+%% <code>false</code>.
+%%
+%% @see char/1
+
+is_char(Node, Value) ->
+    case unwrap(Node) of
+	{char, _, Value} ->
+	    true;
+	#tree{type = char, data = Value} ->
+	    true;
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec char_value(syntaxTree()) -> char()
+%%
+%% @doc Returns the value represented by a <code>char</code> node.
+%%
+%% @see char/1
+
+char_value(Node) ->
+    case unwrap(Node) of
+	{char, _, Char} ->
+	    Char;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec char_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the literal string represented by a <code>char</code>
+%% node. This includes the leading "<code>$</code>" character.
+%%
+%% @see char/1
+
+char_literal(Node) ->
+    io_lib:write_char(char_value(Node)).
+
+
+%% =====================================================================
+%% @spec string(Value::string()) -> syntaxTree()
+%%
+%% @doc Creates an abstract string literal. The result represents
+%% <code>"<em>Text</em>"</code> (including the surrounding
+%% double-quotes), where <code>Text</code> corresponds to the sequence
+%% of characters in <code>Value</code>, but not representing a
+%% <em>specific</em> string literal. E.g., the result of
+%% <code>string("x\ny")</code> represents any and all of
+%% <code>"x\ny"</code>, <code>"x\12y"</code>, <code>"x\012y"</code> and
+%% <code>"x\^Jy"</code>; cf. <code>char/1</code>.
+%%
+%% @see string_value/1
+%% @see string_literal/1
+%% @see is_string/2
+%% @see char/1
+
+%% type(Node) = string
+%% data(Node) = string()
+%%
+%% `erl_parse' representation:
+%%
+%% {string, Pos, Chars}
+%%
+%%	Chars = string()
+
+string(String) ->
+    tree(string, String).
+
+revert_string(Node) ->
+    Pos = get_pos(Node),
+    {string, Pos, string_value(Node)}.
+
+
+%% =====================================================================
+%% @spec is_string(Node::syntaxTree(), Value::string()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> has type
+%% <code>string</code> and represents <code>Value</code>, otherwise
+%% <code>false</code>.
+%%
+%% @see string/1
+
+is_string(Node, Value) ->
+    case unwrap(Node) of
+	{string, _, Value} ->
+	    true;
+	#tree{type = string, data = Value} ->
+	    true;
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec string_value(syntaxTree()) -> string()
+%%
+%% @doc Returns the value represented by a <code>string</code> node.
+%%
+%% @see string/1
+
+string_value(Node) ->
+    case unwrap(Node) of
+	{string, _, List} ->
+	    List;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec string_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the literal string represented by a <code>string</code>
+%% node. This includes surrounding double-quote characters.
+%%
+%% @see string/1
+
+string_literal(Node) ->
+    io_lib:write_string(string_value(Node)).
+
+
+%% =====================================================================
+%% @spec atom(Name) -> syntaxTree()
+%%	    Name = atom() | string()
+%%
+%% @doc Creates an abstract atom literal. The print name of the atom is
+%% the character sequence represented by <code>Name</code>.
+%%
+%% @see atom_value/1
+%% @see atom_name/1
+%% @see atom_literal/1
+%% @see is_atom/2
+
+%% type(Node) = atom
+%% data(Node) = atom()
+%%
+%% `erl_parse' representation:
+%%
+%% {atom, Pos, Value}
+%%
+%%	Value = atom()
+
+atom(Name) when is_atom(Name) ->
+    tree(atom, Name);
+atom(Name) ->
+    tree(atom, list_to_atom(Name)).
+
+revert_atom(Node) ->
+    Pos = get_pos(Node),
+    {atom, Pos, atom_value(Node)}.
+
+
+%% =====================================================================
+%% @spec is_atom(Node::syntaxTree(), Value::atom()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> has type
+%% <code>atom</code> and represents <code>Value</code>, otherwise
+%% <code>false</code>.
+%%
+%% @see atom/1
+
+is_atom(Node, Value) ->
+    case unwrap(Node) of
+	{atom, _, Value} ->
+	    true;
+	#tree{type = atom, data = Value} ->
+	    true;
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec atom_value(syntaxTree()) -> atom()
+%%
+%% @doc Returns the value represented by an <code>atom</code> node.
+%%
+%% @see atom/1
+
+atom_value(Node) ->
+    case unwrap(Node) of
+	{atom, _, Name} ->
+	    Name;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec atom_name(syntaxTree()) -> string()
+%%
+%% @doc Returns the printname of an <code>atom</code> node.
+%%
+%% @see atom/1
+
+atom_name(Node) ->
+    atom_to_list(atom_value(Node)).
+
+
+%% =====================================================================
+%% @spec atom_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the literal string represented by an <code>atom</code>
+%% node. This includes surrounding single-quote characters if necessary.
+%%
+%% <p>Note that e.g. the result of <code>atom("x\ny")</code> represents
+%% any and all of <code>'x\ny'</code>, <code>'x\12y'</code>,
+%% <code>'x\012y'</code> and <code>'x\^Jy\'</code>; cf.
+%% <code>string/1</code>.</p>
+%%
+%% @see atom/1
+%% @see string/1
+
+atom_literal(Node) ->
+    io_lib:write_atom(atom_value(Node)).
+
+
+%% =====================================================================
+%% @spec tuple(Elements::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract tuple. If <code>Elements</code> is
+%% <code>[X1, ..., Xn]</code>, the result represents
+%% "<code>{<em>X1</em>, ..., <em>Xn</em>}</code>".
+%%
+%% <p>Note: The Erlang language has distinct 1-tuples, i.e.,
+%% <code>{X}</code> is always distinct from <code>X</code> itself.</p>
+%%
+%% @see tuple_elements/1
+%% @see tuple_size/1
+
+%% type(Node) = tuple
+%% data(Node) = Elements
+%%
+%%	Elements = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {tuple, Pos, Elements}
+%%
+%%	Elements = [erl_parse()]
+
+tuple(List) ->
+    tree(tuple, List).
+
+revert_tuple(Node) ->
+    Pos = get_pos(Node),
+    {tuple, Pos, tuple_elements(Node)}.
+
+
+%% =====================================================================
+%% @spec tuple_elements(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of element subtrees of a <code>tuple</code>
+%% node.
+%%
+%% @see tuple/1
+
+tuple_elements(Node) ->
+    case unwrap(Node) of
+	{tuple, _, List} ->
+	    List;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec tuple_size(syntaxTree()) -> integer()
+%%
+%% @doc Returns the number of elements of a <code>tuple</code> node.
+%%
+%% <p>Note: this is equivalent to
+%% <code>length(tuple_elements(Node))</code>, but potentially more
+%% efficient.</p>
+%%
+%% @see tuple/1
+%% @see tuple_elements/1
+
+tuple_size(Node) ->
+    length(tuple_elements(Node)).
+
+
+%% =====================================================================
+%% @spec list(List) -> syntaxTree()
+%% @equiv list(List, none)
+
+list(List) ->
+    list(List, none).
+
+
+%% =====================================================================
+%% @spec list(List, Tail) -> syntaxTree()
+%%	    List = [syntaxTree()]
+%%	    Tail = none | syntaxTree()
+%%
+%% @doc Constructs an abstract list skeleton. The result has type
+%% <code>list</code> or <code>nil</code>. If <code>List</code> is a
+%% nonempty list <code>[E1, ..., En]</code>, the result has type
+%% <code>list</code> and represents either "<code>[<em>E1</em>, ...,
+%% <em>En</em>]</code>", if <code>Tail</code> is <code>none</code>, or
+%% otherwise "<code>[<em>E1</em>, ..., <em>En</em> |
+%% <em>Tail</em>]</code>". If <code>List</code> is the empty list,
+%% <code>Tail</code> <em>must</em> be <code>none</code>, and in that
+%% case the result has type <code>nil</code> and represents
+%% "<code>[]</code>" (cf. <code>nil/0</code>).
+%%
+%% <p>The difference between lists as semantic objects (built up of
+%% individual "cons" and "nil" terms) and the various syntactic forms
+%% for denoting lists may be bewildering at first. This module provides
+%% functions both for exact control of the syntactic representation as
+%% well as for the simple composition and deconstruction in terms of
+%% cons and head/tail operations.</p>
+%%
+%% <p>Note: in <code>list(Elements, none)</code>, the "nil" list
+%% terminator is implicit and has no associated information (cf.
+%% <code>get_attrs/1</code>), while in the seemingly equivalent
+%% <code>list(Elements, Tail)</code> when <code>Tail</code> has type
+%% <code>nil</code>, the list terminator subtree <code>Tail</code> may
+%% have attached attributes such as position, comments, and annotations,
+%% which will be preserved in the result.</p>
+%%
+%% @see nil/0
+%% @see list/1
+%% @see list_prefix/1
+%% @see list_suffix/1
+%% @see cons/2
+%% @see list_head/1
+%% @see list_tail/1
+%% @see is_list_skeleton/1
+%% @see is_proper_list/1
+%% @see list_elements/1
+%% @see list_length/1
+%% @see normalize_list/1
+%% @see compact_list/1
+%% @see get_attrs/1
+
+-record(list, {prefix, suffix}).
+
+%% type(Node) = list
+%% data(Node) = #list{prefix :: Elements, suffix :: Tail}
+%%
+%%	    Elements = [syntaxTree()]
+%%	    Tail = none | syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {cons, Pos, Head, Tail}
+%%
+%%	Head = Tail = [erl_parse()]
+%%
+%%	This represents `[<Head> | <Tail>]', or more generally `[<Head>
+%%	<Suffix>]' where the form of <Suffix> can depend on the
+%%	structure of <Tail>; there is no fixed printed form.
+
+list([], none) ->
+    nil();
+list(Elements, Tail) when Elements /= [] ->
+    tree(list, #list{prefix = Elements, suffix = Tail}).
+
+revert_list(Node) ->
+    Pos = get_pos(Node),
+    P = list_prefix(Node),
+    S = case list_suffix(Node) of
+	    none ->
+		revert_nil(set_pos(nil(), Pos));
+	    S1 ->
+		S1
+	end,
+    lists:foldr(fun (X, A) ->
+			{cons, Pos, X, A}
+		end,
+		S, P).
+
+%% =====================================================================
+%% @spec nil() -> syntaxTree()
+%%
+%% @doc Creates an abstract empty list. The result represents
+%% "<code>[]</code>". The empty list is traditionally called "nil".
+%%
+%% @see list/2
+%% @see is_list_skeleton/1
+
+%% type(Node) = nil
+%% data(Node) = term()
+%%
+%% `erl_parse' representation:
+%%
+%% {nil, Pos}
+
+nil() ->
+    tree(nil).
+
+revert_nil(Node) ->
+    Pos = get_pos(Node),
+    {nil, Pos}.
+
+
+%% =====================================================================
+%% @spec list_prefix(Node::syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the prefix element subtrees of a <code>list</code> node.
+%% If <code>Node</code> represents "<code>[<em>E1</em>, ...,
+%% <em>En</em>]</code>" or "<code>[<em>E1</em>, ..., <em>En</em> |
+%% <em>Tail</em>]</code>", the returned value is <code>[E1, ...,
+%% En]</code>.
+%%
+%% @see list/2
+
+list_prefix(Node) ->
+    case unwrap(Node) of
+	{cons, _, Head, _} ->
+	    [Head];
+	Node1 ->
+	    (data(Node1))#list.prefix
+    end.
+
+
+%% =====================================================================
+%% @spec list_suffix(Node::syntaxTree()) ->  none | syntaxTree()
+%%
+%% @doc Returns the suffix subtree of a <code>list</code> node, if one
+%% exists. If <code>Node</code> represents "<code>[<em>E1</em>, ...,
+%% <em>En</em> | <em>Tail</em>]</code>", the returned value is
+%% <code>Tail</code>, otherwise, i.e., if <code>Node</code> represents
+%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", <code>none</code> is
+%% returned.
+%%
+%% <p>Note that even if this function returns some <code>Tail</code>
+%% that is not <code>none</code>, the type of <code>Tail</code> can be
+%% <code>nil</code>, if the tail has been given explicitly, and the list
+%% skeleton has not been compacted (cf.
+%% <code>compact_list/1</code>).</p>
+%%
+%% @see list/2
+%% @see nil/0
+%% @see compact_list/1
+
+list_suffix(Node) ->
+    case unwrap(Node) of
+	{cons, _, _, Tail} ->
+	    %% If there could be comments/annotations on the tail node,
+	    %% we should not return `none' even if it has type `nil'.
+	    case Tail of
+		{nil, _} ->
+		    none;    % no interesting information is lost
+		_ ->
+		    Tail
+	    end;
+	Node1 ->
+	    (data(Node1))#list.suffix
+    end.
+
+
+%% =====================================================================
+%% @spec cons(Head::syntaxTree(), Tail::syntaxTree()) -> syntaxTree()
+%%
+%% @doc "Optimising" list skeleton cons operation. Creates an abstract
+%% list skeleton whose first element is <code>Head</code> and whose tail
+%% corresponds to <code>Tail</code>. This is similar to
+%% <code>list([Head], Tail)</code>, except that <code>Tail</code> may
+%% not be <code>none</code>, and that the result does not necessarily
+%% represent exactly "<code>[<em>Head</em> | <em>Tail</em>]</code>", but
+%% may depend on the <code>Tail</code> subtree. E.g., if
+%% <code>Tail</code> represents <code>[X, Y]</code>, the result may
+%% represent "<code>[<em>Head</em>, X, Y]</code>", rather than
+%% "<code>[<em>Head</em> | [X, Y]]</code>". Annotations on
+%% <code>Tail</code> itself may be lost if <code>Tail</code> represents
+%% a list skeleton, but comments on <code>Tail</code> are propagated to
+%% the result.
+%%
+%% @see list/2
+%% @see list_head/1
+%% @see list_tail/1
+
+cons(Head, Tail) ->
+    case type(Tail) of
+	list ->
+	    copy_comments(Tail, list([Head | list_prefix(Tail)],
+				     list_suffix(Tail)));
+	nil ->
+	    copy_comments(Tail, list([Head]));
+	_ ->
+	    list([Head], Tail)
+    end.
+
+
+%% =====================================================================
+%% @spec list_head(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the head element subtree of a <code>list</code> node. If
+%% <code>Node</code> represents "<code>[<em>Head</em> ...]</code>", the
+%% result will represent "<code><em>Head</em></code>".
+%%
+%% @see list/2
+%% @see list_tail/1
+%% @see cons/2
+
+list_head(Node) ->
+    hd(list_prefix(Node)).
+
+
+%% =====================================================================
+%% @spec list_tail(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the tail of a <code>list</code> node. If
+%% <code>Node</code> represents a single-element list
+%% "<code>[<em>E</em>]</code>", then the result has type
+%% <code>nil</code>, representing "<code>[]</code>". If
+%% <code>Node</code> represents "<code>[<em>E1</em>, <em>E2</em>
+%% ...]</code>", the result will represent "<code>[<em>E2</em>
+%% ...]</code>", and if <code>Node</code> represents
+%% "<code>[<em>Head</em> | <em>Tail</em>]</code>", the result will
+%% represent "<code><em>Tail</em></code>".
+%%
+%% @see list/2
+%% @see list_head/1
+%% @see cons/2
+
+list_tail(Node) ->
+    Tail = list_suffix(Node),
+    case tl(list_prefix(Node)) of
+	[] ->
+	    if Tail =:= none ->
+		    nil();    % implicit list terminator.
+	       true ->
+		    Tail
+	    end;
+	Es ->
+	    list(Es, Tail)    % `Es' is nonempty.
+    end.
+
+
+%% =====================================================================
+%% @spec is_list_skeleton(syntaxTree()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> has type
+%% <code>list</code> or <code>nil</code>, otherwise <code>false</code>.
+%%
+%% @see list/2
+%% @see nil/0
+
+is_list_skeleton(Node) ->
+    case type(Node) of
+	list -> true;
+	nil -> true;
+	_ -> false
+    end.
+
+
+%% =====================================================================
+%% @spec is_proper_list(Node::syntaxTree()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> represents a
+%% proper list, and <code>false</code> otherwise. A proper list is a
+%% list skeleton either on the form "<code>[]</code>" or
+%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", or "<code>[... |
+%% <em>Tail</em>]</code>" where recursively <code>Tail</code> also
+%% represents a proper list.
+%%
+%% <p>Note: Since <code>Node</code> is a syntax tree, the actual
+%% run-time values corresponding to its subtrees may often be partially
+%% or completely unknown. Thus, if <code>Node</code> represents e.g.
+%% "<code>[... | Ns]</code>" (where <code>Ns</code> is a variable), then
+%% the function will return <code>false</code>, because it is not known
+%% whether <code>Ns</code> will be bound to a list at run-time. If
+%% <code>Node</code> instead represents e.g. "<code>[1, 2, 3]</code>" or
+%% "<code>[A | []]</code>", then the function will return
+%% <code>true</code>.</p>
+%%
+%% @see list/2
+
+is_proper_list(Node) ->
+    case type(Node) of
+	list ->
+	    case list_suffix(Node) of
+		none ->
+		    true;
+		Tail ->
+		    is_proper_list(Tail)
+	    end;
+	nil ->
+	    true;
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec list_elements(Node::syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of element subtrees of a list skeleton.
+%% <code>Node</code> must represent a proper list. E.g., if
+%% <code>Node</code> represents "<code>[<em>X1</em>, <em>X2</em> |
+%% [<em>X3</em>, <em>X4</em> | []]</code>", then
+%% <code>list_elements(Node)</code> yields the list <code>[X1, X2, X3,
+%% X4]</code>.
+%%
+%% @see list/2
+%% @see is_proper_list/1
+
+list_elements(Node) ->
+    lists:reverse(list_elements(Node, [])).
+
+list_elements(Node, As) ->
+    case type(Node) of
+	list ->
+	    As1 = lists:reverse(list_prefix(Node)) ++ As,
+	    case list_suffix(Node) of
+		none ->
+		    As1;
+		Tail ->
+		    list_elements(Tail, As1)
+	    end;
+	nil ->
+	    As
+    end.
+
+
+%% =====================================================================
+%% @spec list_length(Node::syntaxTree()) -> integer()
+%%
+%% @doc Returns the number of element subtrees of a list skeleton.
+%% <code>Node</code> must represent a proper list. E.g., if
+%% <code>Node</code> represents "<code>[X1 | [X2, X3 | [X4, X5,
+%% X6]]]</code>", then <code>list_length(Node)</code> returns the
+%% integer 6.
+%%
+%% <p>Note: this is equivalent to
+%% <code>length(list_elements(Node))</code>, but potentially more
+%% efficient.</p>
+%%
+%% @see list/2
+%% @see is_proper_list/1
+%% @see list_elements/1
+
+list_length(Node) ->
+    list_length(Node, 0).
+
+list_length(Node, A) ->
+    case type(Node) of
+	list ->
+	    A1 = length(list_prefix(Node)) + A,
+	    case list_suffix(Node) of
+		none ->
+		    A1;
+		Tail ->
+		    list_length(Tail, A1)
+	    end;
+	nil ->
+	    A
+    end.
+
+
+%% =====================================================================
+%% @spec normalize_list(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Expands an abstract list skeleton to its most explicit form. If
+%% <code>Node</code> represents "<code>[<em>E1</em>, ..., <em>En</em> |
+%% <em>Tail</em>]</code>", the result represents "<code>[<em>E1</em> |
+%% ... [<em>En</em> | <em>Tail1</em>] ... ]</code>", where
+%% <code>Tail1</code> is the result of
+%% <code>normalize_list(Tail)</code>. If <code>Node</code> represents
+%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", the result simply
+%% represents "<code>[<em>E1</em> | ... [<em>En</em> | []] ...
+%% ]</code>". If <code>Node</code> does not represent a list skeleton,
+%% <code>Node</code> itself is returned.
+%%
+%% @see list/2
+%% @see compact_list/1
+
+normalize_list(Node) ->
+    case type(Node) of
+	list ->
+	    P = list_prefix(Node),
+	    case list_suffix(Node) of
+		none ->
+		    copy_attrs(Node, normalize_list_1(P, nil()));
+		Tail ->
+		    Tail1 = normalize_list(Tail),
+		    copy_attrs(Node, normalize_list_1(P, Tail1))
+	    end;
+	_ ->
+	    Node
+    end.
+
+normalize_list_1(Es, Tail) ->
+    lists:foldr(fun (X, A) ->
+			list([X], A)    % not `cons'!
+		end,
+		Tail, Es).
+
+
+%% =====================================================================
+%% @spec compact_list(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Yields the most compact form for an abstract list skeleton. The
+%% result either represents "<code>[<em>E1</em>, ..., <em>En</em> |
+%% <em>Tail</em>]</code>", where <code>Tail</code> is not a list
+%% skeleton, or otherwise simply "<code>[<em>E1</em>, ...,
+%% <em>En</em>]</code>". Annotations on subtrees of <code>Node</code>
+%% that represent list skeletons may be lost, but comments will be
+%% propagated to the result. Returns <code>Node</code> itself if
+%% <code>Node</code> does not represent a list skeleton.
+%%
+%% @see list/2
+%% @see normalize_list/1
+
+compact_list(Node) ->
+    case type(Node) of
+	list ->
+	    case list_suffix(Node) of
+		none ->
+		    Node;
+		Tail ->
+		    case type(Tail) of
+			list ->
+			    Tail1 = compact_list(Tail),
+			    Node1 = list(list_prefix(Node) ++
+					 list_prefix(Tail1),
+					 list_suffix(Tail1)),
+			    join_comments(Tail1,
+					  copy_attrs(Node,
+						     Node1));
+			nil ->
+			    Node1 = list(list_prefix(Node)),
+			    join_comments(Tail,
+					  copy_attrs(Node,
+						     Node1));
+			_ ->
+			    Node 
+		    end
+	    end;
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec binary(Fields::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract binary-object template. If
+%% <code>Fields</code> is <code>[F1, ..., Fn]</code>, the result
+%% represents "<code>&lt;&lt;<em>F1</em>, ...,
+%% <em>Fn</em>&gt;&gt;</code>".
+%%
+%% @see binary_fields/1
+%% @see binary_field/2
+
+%% type(Node) = binary
+%% data(Node) = Fields
+%%
+%%	Fields = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {bin, Pos, Fields}
+%%
+%%	Fields = [Field]
+%%	Field = {bin_element, ...}
+%%
+%%	See `binary_field' for documentation on `erl_parse' binary
+%%	fields (or "elements").
+
+binary(List) ->
+    tree(binary, List).
+
+revert_binary(Node) ->
+    Pos = get_pos(Node),
+    {bin, Pos, binary_fields(Node)}.
+
+
+%% =====================================================================
+%% @spec binary_fields(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of field subtrees of a <code>binary</code>
+%% node.
+%%
+%% @see binary/1
+%% @see binary_field/2
+
+binary_fields(Node) ->
+    case unwrap(Node) of
+	{bin, _, List} ->
+	    List;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec binary_field(Body) -> syntaxTree()
+%% @equiv binary_field(Body, [])
+
+binary_field(Body) ->
+    binary_field(Body, []).
+
+
+%% =====================================================================
+%% @spec binary_field(Body::syntaxTree(), Size,
+%%                    Types::[syntaxTree()]) -> syntaxTree()
+%%	    Size = none | syntaxTree()
+%%
+%% @doc Creates an abstract binary template field.
+%% If <code>Size</code> is <code>none</code>, this is equivalent to
+%% "<code>binary_field(Body, Types)</code>", otherwise it is
+%% equivalent to "<code>binary_field(size_qualifier(Body, Size),
+%% Types)</code>".
+%%
+%% (This is a utility function.)
+%%
+%% @see binary/1
+%% @see binary_field/2
+%% @see size_qualifier/2
+
+binary_field(Body, none, Types) ->
+    binary_field(Body, Types);
+binary_field(Body, Size, Types) ->
+    binary_field(size_qualifier(Body, Size), Types).
+
+
+%% =====================================================================
+%% @spec binary_field(Body::syntaxTree(), Types::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract binary template field. If
+%% <code>Types</code> is the empty list, the result simply represents
+%% "<code><em>Body</em></code>", otherwise, if <code>Types</code> is
+%% <code>[T1, ..., Tn]</code>, the result represents
+%% "<code><em>Body</em>/<em>T1</em>-...-<em>Tn</em></code>".
+%%
+%% @see binary/1
+%% @see binary_field/1
+%% @see binary_field/3
+%% @see binary_field_body/1
+%% @see binary_field_types/1
+%% @see binary_field_size/1
+
+-record(binary_field, {body, types}).
+
+%% type(Node) = binary_field
+%% data(Node) = #binary_field{body :: Body, types :: Types}
+%%
+%%	    Body = syntaxTree()
+%%	    Types = [Type]
+%%
+%% `erl_parse' representation:
+%%
+%% {bin_element, Pos, Expr, Size, TypeList}
+%%
+%%	Expr = erl_parse()
+%%	Size = default | erl_parse()
+%%	TypeList = default | [Type] \ []
+%%	Type = atom() | {atom(), integer()}
+
+binary_field(Body, Types) ->
+    tree(binary_field, #binary_field{body = Body, types = Types}).
+
+revert_binary_field(Node) ->
+    Pos = get_pos(Node),
+    Body = binary_field_body(Node),
+    {Expr, Size} = case type(Body) of
+		       size_qualifier ->
+			   %% Note that size qualifiers are not
+			   %% revertible out of context.
+			   {size_qualifier_body(Body),
+			    size_qualifier_argument(Body)};
+		       _ ->
+			   {Body, default}
+		   end,
+    Types = case binary_field_types(Node) of
+		[] ->
+		    default;
+		Ts ->
+		    fold_binary_field_types(Ts)
+	    end,
+    {bin_element, Pos, Expr, Size, Types}.
+
+
+%% =====================================================================
+%% @spec binary_field_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>binary_field</code>.
+%%
+%% @see binary_field/2
+
+binary_field_body(Node) ->
+    case unwrap(Node) of
+	{bin_element, _, Body, Size, _} ->
+	    if Size =:= default ->
+		    Body;
+	       true ->
+		    size_qualifier(Body, Size)
+	    end;
+	Node1 ->
+	    (data(Node1))#binary_field.body
+    end.
+
+
+%% =====================================================================
+%% @spec binary_field_types(Node::syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of type-specifier subtrees of a
+%% <code>binary_field</code> node. If <code>Node</code> represents
+%% "<code>.../<em>T1</em>, ..., <em>Tn</em></code>", the result is
+%% <code>[T1, ..., Tn]</code>, otherwise the result is the empty list.
+%%
+%% @see binary_field/2
+
+binary_field_types(Node) ->
+    case unwrap(Node) of
+	{bin_element, Pos, _, _, Types} ->
+	    if Types =:= default ->
+		    [];
+	       true ->
+		    unfold_binary_field_types(Types, Pos)
+	    end;
+	Node1 ->
+	    (data(Node1))#binary_field.types
+    end.
+
+
+%% =====================================================================
+%% @spec binary_field_size(Node::syntaxTree()) -> none | syntaxTree()
+%%
+%% @doc Returns the size specifier subtree of a
+%% <code>binary_field</code> node, if any. If <code>Node</code>
+%% represents "<code><em>Body</em>:<em>Size</em></code>" or
+%% "<code><em>Body</em>:<em>Size</em>/<em>T1</em>, ...,
+%% <em>Tn</em></code>", the result is <code>Size</code>, otherwise
+%% <code>none</code> is returned.
+%%
+%% (This is a utility function.)
+%%
+%% @see binary_field/2
+%% @see binary_field/3
+
+binary_field_size(Node) ->
+    case unwrap(Node) of
+	{bin_element, _, _, Size, _} ->
+	    if Size =:= default ->
+		    none;
+	       true ->
+		    Size
+	    end;
+	Node1 ->
+	    Body = (data(Node1))#binary_field.body,
+	    case type(Body) of
+		size_qualifier ->
+		    size_qualifier_argument(Body);
+		_ ->
+		    none
+	    end
+    end.
+
+
+%% =====================================================================
+%% @spec size_qualifier(Body::syntaxTree(), Size::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract size qualifier. The result represents
+%% "<code><em>Body</em>:<em>Size</em></code>".
+%%
+%% @see size_qualifier_body/1
+%% @see size_qualifier_argument/1
+
+-record(size_qualifier, {body, size}).
+
+%% type(Node) = size_qualifier
+%% data(Node) = #size_qualifier{body :: Body, size :: Size}
+%%
+%%	Body = Size = syntaxTree()
+
+size_qualifier(Body, Size) ->
+    tree(size_qualifier,
+	 #size_qualifier{body = Body, size = Size}).
+
+
+%% =====================================================================
+%% @spec size_qualifier_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>size_qualifier</code>
+%% node.
+%%
+%% @see size_qualifier/2
+
+size_qualifier_body(Node) ->
+    (data(Node))#size_qualifier.body.
+
+
+%% =====================================================================
+%% @spec size_qualifier_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument subtree (the size) of a
+%% <code>size_qualifier</code> node.
+%%
+%% @see size_qualifier/2
+
+size_qualifier_argument(Node) ->
+    (data(Node))#size_qualifier.size.
+
+
+%% =====================================================================
+%% @spec error_marker(Error::term()) -> syntaxTree()
+%%
+%% @doc Creates an abstract error marker. The result represents an
+%% occurrence of an error in the source code, with an associated Erlang
+%% I/O ErrorInfo structure given by <code>Error</code> (see module
+%% {@link //stdlib/io} for details). Error markers are regarded as source
+%% code forms, but have no defined lexical form.
+%%
+%% <p>Note: this is supported only for backwards compatibility with
+%% existing parsers and tools.</p>
+%%
+%% @see error_marker_info/1
+%% @see warning_marker/1
+%% @see eof_marker/0
+%% @see is_form/1
+
+%% type(Node) = error_marker
+%% data(Node) = term()
+%%
+%% `erl_parse' representation:
+%%
+%% {error, Error}
+%%
+%%	Error = term()
+%%
+%%	Note that there is no position information for the node
+%%	itself: `get_pos' and `set_pos' handle this as a special case.
+
+error_marker(Error) ->
+    tree(error_marker, Error).
+
+revert_error_marker(Node) ->
+    %% Note that the position information of the node itself is not
+    %% preserved.
+    {error, error_marker_info(Node)}.
+
+
+%% =====================================================================
+%% @spec error_marker_info(syntaxTree()) -> term()
+%%
+%% @doc Returns the ErrorInfo structure of an <code>error_marker</code>
+%% node.
+%%
+%% @see error_marker/1
+
+error_marker_info(Node) ->
+    case unwrap(Node) of
+	{error, Error} ->
+	    Error;
+	T ->
+	    data(T)
+    end.
+
+
+%% =====================================================================
+%% @spec warning_marker(Error::term()) -> syntaxTree()
+%%
+%% @doc Creates an abstract warning marker. The result represents an
+%% occurrence of a possible problem in the source code, with an
+%% associated Erlang I/O ErrorInfo structure given by <code>Error</code>
+%% (see module {@link //stdlib/io} for details). Warning markers are
+%% regarded as source code forms, but have no defined lexical form.
+%%
+%% <p>Note: this is supported only for backwards compatibility with
+%% existing parsers and tools.</p>
+%%
+%% @see warning_marker_info/1
+%% @see error_marker/1
+%% @see eof_marker/0
+%% @see is_form/1
+
+%% type(Node) = warning_marker
+%% data(Node) = term()
+%%
+%% `erl_parse' representation:
+%%
+%% {warning, Error}
+%%
+%%	Error = term()
+%%
+%%	Note that there is no position information for the node
+%%	itself: `get_pos' and `set_pos' handle this as a special case.
+
+warning_marker(Warning) ->
+    tree(warning_marker, Warning).
+
+revert_warning_marker(Node) ->
+    %% Note that the position information of the node itself is not
+    %% preserved.
+    {warning, warning_marker_info(Node)}.
+
+
+%% =====================================================================
+%% @spec warning_marker_info(syntaxTree()) -> term()
+%%
+%% @doc Returns the ErrorInfo structure of a <code>warning_marker</code>
+%% node.
+%%
+%% @see warning_marker/1
+
+warning_marker_info(Node) ->
+    case unwrap(Node) of
+	{warning, Error} ->
+	    Error;
+	T ->
+	    data(T)
+    end.
+
+
+%% =====================================================================
+%% @spec eof_marker() -> syntaxTree()
+%%
+%% @doc Creates an abstract end-of-file marker. This represents the
+%% end of input when reading a sequence of source code forms. An
+%% end-of-file marker is itself regarded as a source code form
+%% (namely, the last in any sequence in which it occurs). It has no
+%% defined lexical form.
+%%
+%% <p>Note: this is retained only for backwards compatibility with
+%% existing parsers and tools.</p>
+%%
+%% @see error_marker/1
+%% @see warning_marker/1
+%% @see is_form/1
+
+%% type(Node) = eof_marker
+%% data(Node) = term()
+%%
+%% `erl_parse' representation:
+%%
+%% {eof, Pos}
+
+eof_marker() ->
+    tree(eof_marker).
+
+revert_eof_marker(Node) ->
+    Pos = get_pos(Node),
+    {eof, Pos}.
+
+
+%% =====================================================================
+%% @spec attribute(Name) -> syntaxTree()
+%% @equiv attribute(Name, none)
+
+attribute(Name) ->
+    attribute(Name, none).
+
+
+%% =====================================================================
+%% @spec attribute(Name::syntaxTree(), Arguments) -> syntaxTree()
+%%           Arguments = none | [syntaxTree()]
+%%
+%% @doc Creates an abstract program attribute. If
+%% <code>Arguments</code> is <code>[A1, ..., An]</code>, the result
+%% represents "<code>-<em>Name</em>(<em>A1</em>, ...,
+%% <em>An</em>).</code>". Otherwise, if <code>Arguments</code> is
+%% <code>none</code>, the result represents
+%% "<code>-<em>Name</em>.</code>". The latter form makes it possible
+%% to represent preprocessor directives such as
+%% "<code>-endif.</code>". Attributes are source code forms.
+%%
+%% <p>Note: The preprocessor macro definition directive
+%% "<code>-define(<em>Name</em>, <em>Body</em>).</code>" has relatively
+%% few requirements on the syntactical form of <code>Body</code> (viewed
+%% as a sequence of tokens). The <code>text</code> node type can be used
+%% for a <code>Body</code> that is not a normal Erlang construct.</p>
+%%
+%% @see attribute/1
+%% @see attribute_name/1
+%% @see attribute_arguments/1
+%% @see text/1
+%% @see is_form/1
+
+-record(attribute, {name, args}).
+
+%% type(Node) = attribute
+%% data(Node) = #attribute{name :: Name, args :: Arguments}
+%%
+%%	Name = syntaxTree()
+%%	Arguments = none | [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {attribute, Pos, module, {Name,Vars}}
+%% {attribute, Pos, module, Name}
+%%
+%%	Name = atom() | [atom()]
+%%	Vars = [atom()]
+%%
+%%	Representing `-module(M).', or `-module(M, Vs).', where M is
+%%	`A1.A2.....An' if Name is `[A1, A2, ..., An]', and Vs is `[V1,
+%%	..., Vm]' if Vars is `[V1, ..., Vm]'.
+%%
+%% {attribute, Pos, export, Exports}
+%%
+%%	Exports = [{atom(), integer()}]
+%%
+%%	Representing `-export([A1/N1, ..., Ak/Nk]).', if `Exports' is
+%%	`[{A1, N1}, ..., {Ak, Nk}]'.
+%%
+%% {attribute, Pos, import, Imports}
+%%
+%%	Imports = {atom(), Pairs} | [atom()]
+%%	Pairs = [{atom(), integer()]
+%%
+%%	Representing `-import(Module, [A1/N1, ..., Ak/Nk]).', if
+%%	`Imports' is `{Module, [{A1, N1}, ..., {Ak, Nk}]}', or
+%%	`-import(A1.....An).', if `Imports' is `[A1, ..., An]'.
+%%
+%% {attribute, Pos, file, Position}
+%%
+%%	Position = {filename(), integer()}
+%%
+%%	Representing `-file(Name, Line).', if `Position' is `{Name,
+%%	Line}'.
+%%
+%% {attribute, Pos, record, Info}
+%%
+%%	Info = {Name, [Entries]}
+%%	Name = atom()
+%%	Entries = {record_field, Pos, atom()}
+%%		| {record_field, Pos, atom(), erl_parse()}
+%%
+%%	Representing `-record(Name, {<F1>, ..., <Fn>}).', if `Info' is
+%%	`{Name, [D1, ..., D1]}', where each `Fi' is either `Ai = <Ei>',
+%%	if the corresponding `Di' is `{record_field, Pos, Ai, Ei}', or
+%%	otherwise simply `Ai', if `Di' is `{record_field, Pos, Ai}'.
+%%
+%% {attribute, L, Name, Term}
+%%
+%%	Name = atom() \ StandardName
+%%	StandardName = module | export | import | file | record
+%%	Term = term()
+%%
+%%	Representing `-Name(Term).'.
+
+attribute(Name, Args) ->
+    tree(attribute, #attribute{name = Name, args = Args}).
+
+revert_attribute(Node) ->
+    Name = attribute_name(Node),
+    Args = attribute_arguments(Node),
+    Pos = get_pos(Node),
+    case type(Name) of
+	atom ->
+	    revert_attribute_1(atom_value(Name), Args, Pos, Node);
+	_ ->
+	    Node
+    end.
+
+%% All the checking makes this part a bit messy:
+
+revert_attribute_1(module, [M], Pos, Node) ->
+    case revert_module_name(M) of
+	{ok, A} -> 
+	    {attribute, Pos, module, A};
+	error -> Node
+    end;
+revert_attribute_1(module, [M, List], Pos, Node) ->
+    Vs = case is_list_skeleton(List) of
+	     true ->
+		 case is_proper_list(List) of
+		     true ->
+			 fold_variable_names(list_elements(List));
+		     false ->
+			 Node
+		 end;
+	     false ->
+		 Node
+	 end,
+    case revert_module_name(M) of
+	{ok, A} -> 
+	    {attribute, Pos, module, {A, Vs}};
+	error -> Node
+    end;
+revert_attribute_1(export, [List], Pos, Node) ->
+    case is_list_skeleton(List) of
+	true ->
+	    case is_proper_list(List) of
+		true ->
+		    Fs = fold_function_names(list_elements(List)),
+		    {attribute, Pos, export, Fs};
+		false ->
+		    Node
+	    end;
+	false ->
+	    Node
+    end;
+revert_attribute_1(import, [M], Pos, Node) ->
+    case revert_module_name(M) of
+	{ok, A} -> {attribute, Pos, import, A};
+	error -> Node
+    end;
+revert_attribute_1(import, [M, List], Pos, Node) ->
+    case revert_module_name(M) of
+	{ok, A} ->
+	    case is_list_skeleton(List) of
+		true ->
+		    case is_proper_list(List) of
+			true ->
+			    Fs = fold_function_names(
+				   list_elements(List)),
+			    {attribute, Pos, import, {A, Fs}};
+			false ->
+			    Node
+		    end;
+		false ->
+		    Node
+	    end;
+	error ->
+	    Node
+    end;
+revert_attribute_1(file, [A, Line], Pos, Node) ->
+    case type(A) of
+	string ->
+	    case type(Line) of
+		integer ->
+		    {attribute, Pos, file,
+		     {concrete(A), concrete(Line)}};
+		_ ->
+		    Node
+	    end;
+	_ ->
+	    Node
+    end;
+revert_attribute_1(record, [A, Tuple], Pos, Node) ->
+    case type(A) of
+	atom ->
+	    case type(Tuple) of
+		tuple ->
+		    Fs = fold_record_fields(
+			   tuple_elements(Tuple)),
+		    {attribute, Pos, record, {concrete(A), Fs}};
+		_ ->
+		    Node
+	    end;
+	_ ->
+	    Node
+    end;
+revert_attribute_1(N, [T], Pos, _) ->
+    {attribute, Pos, N, concrete(T)};
+revert_attribute_1(_, _, _, Node) ->
+    Node.
+
+revert_module_name(A) ->
+    case type(A) of
+	atom ->
+	    {ok, concrete(A)};
+	qualified_name ->
+	    Ss = qualified_name_segments(A),
+	    {ok, [concrete(S) || S <- Ss]};
+	_ ->
+	    error
+    end.
+
+
+%% =====================================================================
+%% @spec attribute_name(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of an <code>attribute</code> node.
+%%
+%% @see attribute/1
+
+attribute_name(Node) ->
+    case unwrap(Node) of
+	{attribute, Pos, Name, _} ->
+	    set_pos(atom(Name), Pos);
+	Node1 ->
+	    (data(Node1))#attribute.name
+    end.
+
+
+%% =====================================================================
+%% @spec attribute_arguments(Node::syntaxTree()) ->
+%%           none | [syntaxTree()]
+%%
+%% @doc Returns the list of argument subtrees of an
+%% <code>attribute</code> node, if any. If <code>Node</code>
+%% represents "<code>-<em>Name</em>.</code>", the result is
+%% <code>none</code>. Otherwise, if <code>Node</code> represents
+%% "<code>-<em>Name</em>(<em>E1</em>, ..., <em>En</em>).</code>",
+%% <code>[E1, ..., E1]</code> is returned.
+%%
+%% @see attribute/1
+
+attribute_arguments(Node) ->
+    case unwrap(Node) of
+	{attribute, Pos, Name, Data} ->
+	    case Name of
+		module ->
+		    {M1, Vs} =
+			case Data of
+			    {M0, Vs0} ->
+				{M0, unfold_variable_names(Vs0, Pos)};
+			    M0 ->
+				{M0, none}
+			end,
+		    M2 = if is_list(M1) ->
+				 qualified_name([atom(A) || A <- M1]);
+			    true ->
+				 atom(M1)
+			 end,
+		    M = set_pos(M2, Pos),
+		    if Vs == none -> [M];
+		       true -> [M, set_pos(list(Vs), Pos)]
+		    end;
+		export ->
+		    [set_pos(
+		       list(unfold_function_names(Data, Pos)),
+		       Pos)];
+		import ->
+		    case Data of
+			{Module, Imports} ->
+			    [if is_list(Module) ->
+				     qualified_name([atom(A)
+						     || A <- Module]);
+				true ->
+				     set_pos(atom(Module), Pos)
+			     end,
+			     set_pos(
+			       list(unfold_function_names(Imports, Pos)),
+			       Pos)];
+			_ ->
+			    [qualified_name([atom(A) || A <- Data])]
+		    end;
+		file ->
+		    {File, Line} = Data,
+		    [set_pos(string(File), Pos),
+		     set_pos(integer(Line), Pos)];
+		record ->
+		    %% Note that we create a tuple as container
+		    %% for the second argument!
+		    {Type, Entries} = Data,
+		    [set_pos(atom(Type), Pos),
+		     set_pos(tuple(unfold_record_fields(Entries)),
+			     Pos)];
+		_ ->
+		    %% Standard single-term generic attribute.
+		    [set_pos(abstract(Data), Pos)]
+	    end;
+	Node1 ->
+	    (data(Node1))#attribute.args
+    end.
+
+
+%% =====================================================================
+%% @spec arity_qualifier(Body::syntaxTree(), Arity::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract arity qualifier. The result represents
+%% "<code><em>Body</em>/<em>Arity</em></code>".
+%%
+%% @see arity_qualifier_body/1
+%% @see arity_qualifier_argument/1
+
+-record(arity_qualifier, {body, arity}).
+
+%% type(Node) = arity_qualifier
+%% data(Node) = #arity_qualifier{body :: Body, arity :: Arity}
+%%
+%%	Body = Arity = syntaxTree()
+
+arity_qualifier(Body, Arity) ->
+    tree(arity_qualifier,
+	 #arity_qualifier{body = Body, arity = Arity}).
+
+
+%% =====================================================================
+%% @spec arity_qualifier_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of an <code>arity_qualifier</code>
+%% node.
+%%
+%% @see arity_qualifier/2
+
+arity_qualifier_body(Node) ->
+    (data(Node))#arity_qualifier.body.
+
+
+%% =====================================================================
+%% @spec arity_qualifier_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument (the arity) subtree of an
+%% <code>arity_qualifier</code> node.
+%%
+%% @see arity_qualifier/2
+
+arity_qualifier_argument(Node) ->
+    (data(Node))#arity_qualifier.arity.
+
+
+%% =====================================================================
+%% @spec module_qualifier(Module::syntaxTree(), Body::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract module qualifier. The result represents
+%% "<code><em>Module</em>:<em>Body</em></code>".
+%%
+%% @see module_qualifier_argument/1
+%% @see module_qualifier_body/1
+
+-record(module_qualifier, {module, body}).
+
+%% type(Node) = module_qualifier
+%% data(Node) = #module_qualifier{module :: Module, body :: Body}
+%%
+%%	Module = Body = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {remote, Pos, Module, Arg}
+%%
+%%	Module = Arg = erl_parse()
+
+module_qualifier(Module, Body) ->
+    tree(module_qualifier,
+	 #module_qualifier{module = Module, body = Body}).
+
+revert_module_qualifier(Node) ->
+    Pos = get_pos(Node),
+    Module = module_qualifier_argument(Node),
+    Body = module_qualifier_body(Node),
+    {remote, Pos, Module, Body}.
+
+
+%% =====================================================================
+%% @spec module_qualifier_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument (the module) subtree of a
+%% <code>module_qualifier</code> node.
+%%
+%% @see module_qualifier/2
+
+module_qualifier_argument(Node) ->
+    case unwrap(Node) of
+	{remote, _, Module, _} ->
+	    Module;
+	Node1 ->
+	    (data(Node1))#module_qualifier.module
+    end.
+
+
+%% =====================================================================
+%% @spec module_qualifier_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>module_qualifier</code>
+%% node.
+%%
+%% @see module_qualifier/2
+
+module_qualifier_body(Node) ->
+    case unwrap(Node) of
+	{remote, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#module_qualifier.body
+    end.
+
+
+%% =====================================================================
+%% @spec qualified_name(Segments::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract qualified name. The result represents
+%% "<code><em>S1</em>.<em>S2</em>. ... .<em>Sn</em></code>", if
+%% <code>Segments</code> is <code>[S1, S2, ..., Sn]</code>.
+%%
+%% @see qualified_name_segments/1
+
+%% type(Node) = qualified_name
+%% data(Node) = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {record_field, Pos, Node, Node}
+%%
+%%	Node = {atom, Pos, Value} | {record_field, Pos, Node, Node}
+%%
+%% Note that if not all leaf subnodes are (abstract) atoms, then Node
+%% represents a Mnemosyne query record field access ('record_access');
+%% see type/1 for details.
+
+qualified_name(Segments) ->
+    tree(qualified_name, Segments).
+
+revert_qualified_name(Node) ->
+    Pos = get_pos(Node),
+    fold_qualified_name(qualified_name_segments(Node), Pos).
+
+
+%% =====================================================================
+%% @spec qualified_name_segments(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of name segments of a
+%% <code>qualified_name</code> node.
+%%
+%% @see qualified_name/1
+
+qualified_name_segments(Node) ->
+    case unwrap(Node) of
+	{record_field, _, _, _} = Node1 ->
+	    unfold_qualified_name(Node1);
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec function(Name::syntaxTree(), Clauses::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract function definition. If <code>Clauses</code>
+%% is <code>[C1, ..., Cn]</code>, the result represents
+%% "<code><em>Name</em> <em>C1</em>; ...; <em>Name</em>
+%% <em>Cn</em>.</code>". More exactly, if each <code>Ci</code>
+%% represents "<code>(<em>Pi1</em>, ..., <em>Pim</em>) <em>Gi</em> ->
+%% <em>Bi</em></code>", then the result represents
+%% "<code><em>Name</em>(<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> ->
+%% <em>B1</em>; ...; <em>Name</em>(<em>Pn1</em>, ..., <em>Pnm</em>)
+%% <em>Gn</em> -> <em>Bn</em>.</code>". Function definitions are source
+%% code forms.
+%%
+%% @see function_name/1
+%% @see function_clauses/1
+%% @see function_arity/1
+%% @see is_form/1
+%% @see rule/2
+
+-record(function, {name, clauses}).
+
+%% type(Node) = function
+%% data(Node) = #function{name :: Name, clauses :: Clauses}
+%%
+%%	Name = syntaxTree()
+%%	Clauses = [syntaxTree()]
+%%
+%%	(There's no real point in precomputing and storing the arity,
+%%	and passing it as a constructor argument makes it possible to
+%%	end up with an inconsistent value. Besides, some people might
+%%	want to check all clauses, and not just the first, so the
+%%	computation is not obvious.)
+%%
+%% `erl_parse' representation:
+%%
+%% {function, Pos, Name, Arity, Clauses}
+%%
+%%	Name = atom()
+%%	Arity = integer()
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	where the number of patterns in each clause should be equal to
+%%	the integer `Arity'; see `clause' for documentation on
+%%	`erl_parse' clauses.
+
+function(Name, Clauses) ->
+    tree(function, #function{name = Name, clauses = Clauses}).
+
+revert_function(Node) ->
+    Name = function_name(Node),
+    Clauses = [revert_clause(C) || C <- function_clauses(Node)],
+    Pos = get_pos(Node),
+    case type(Name) of
+	atom ->
+	    A = function_arity(Node),
+	    {function, Pos, concrete(Name), A, Clauses};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec function_name(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of a <code>function</code> node.
+%%
+%% @see function/2
+
+function_name(Node) ->
+    case unwrap(Node) of
+	{function, Pos, Name, _, _} ->
+	    set_pos(atom(Name), Pos);
+	Node1 ->
+	    (data(Node1))#function.name
+    end.
+
+
+%% =====================================================================
+%% @spec function_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of a <code>function</code>
+%% node.
+%%
+%% @see function/2
+
+function_clauses(Node) ->
+    case unwrap(Node) of
+	{function, _, _, _, Clauses} ->
+	    Clauses;
+	Node1 ->
+	    (data(Node1))#function.clauses
+    end.
+
+
+%% =====================================================================
+%% @spec function_arity(Node::syntaxTree()) -> integer()
+%%
+%% @doc Returns the arity of a <code>function</code> node. The result
+%% is the number of parameter patterns in the first clause of the
+%% function; subsequent clauses are ignored.
+%%
+%% <p>An exception is thrown if <code>function_clauses(Node)</code>
+%% returns an empty list, or if the first element of that list is not
+%% a syntax tree <code>C</code> of type <code>clause</code> such that
+%% <code>clause_patterns(C)</code> is a nonempty list.</p>
+%%
+%% @see function/2
+%% @see function_clauses/1
+%% @see clause/3
+%% @see clause_patterns/1
+
+function_arity(Node) ->
+    %% Note that this never accesses the arity field of `erl_parse'
+    %% function nodes.
+    length(clause_patterns(hd(function_clauses(Node)))).
+
+
+%% =====================================================================
+%% @spec clause(Guard, Body) -> syntaxTree()
+%% @equiv clause([], Guard, Body)
+
+clause(Guard, Body) ->
+    clause([], Guard, Body).
+
+
+%% =====================================================================
+%% @spec clause(Patterns::[syntaxTree()], Guard,
+%%              Body::[syntaxTree()]) -> syntaxTree()
+%%	    Guard = none | syntaxTree()
+%%                | [syntaxTree()] | [[syntaxTree()]]
+%%
+%% @doc Creates an abstract clause. If <code>Patterns</code> is
+%% <code>[P1, ..., Pn]</code> and <code>Body</code> is <code>[B1, ...,
+%% Bm]</code>, then if <code>Guard</code> is <code>none</code>, the
+%% result represents "<code>(<em>P1</em>, ..., <em>Pn</em>) ->
+%% <em>B1</em>, ..., <em>Bm</em></code>", otherwise, unless
+%% <code>Guard</code> is a list, the result represents
+%% "<code>(<em>P1</em>, ..., <em>Pn</em>) when <em>Guard</em> ->
+%% <em>B1</em>, ..., <em>Bm</em></code>".
+%%
+%% <p>For simplicity, the <code>Guard</code> argument may also be any
+%% of the following:
+%% <ul>
+%%   <li>An empty list <code>[]</code>. This is equivalent to passing
+%%       <code>none</code>.</li>
+%%   <li>A nonempty list <code>[E1, ..., Ej]</code> of syntax trees.
+%%       This is equivalent to passing <code>conjunction([E1, ...,
+%%       Ej])</code>.</li>
+%%   <li>A nonempty list of lists of syntax trees <code>[[E1_1, ...,
+%%       E1_k1], ..., [Ej_1, ..., Ej_kj]]</code>, which is equivalent
+%%       to passing <code>disjunction([conjunction([E1_1, ...,
+%%       E1_k1]), ..., conjunction([Ej_1, ..., Ej_kj])])</code>.</li>
+%% </ul>
+%% </p>
+%%
+%% @see clause/2
+%% @see clause_patterns/1
+%% @see clause_guard/1
+%% @see clause_body/1
+
+-record(clause, {patterns, guard, body}).
+
+%% type(Node) = clause
+%% data(Node) = #clause{patterns :: Patterns, guard :: Guard,
+%%		        body :: Body}
+%%
+%%	Patterns = [syntaxTree()]
+%%	Guard = syntaxTree() | none
+%%	Body = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {clause, Pos, Patterns, Guard, Body}
+%%
+%%	Patterns = [erl_parse()]
+%%	Guard = [[erl_parse()]] | [erl_parse()]
+%%	Body = [erl_parse()] \ []
+%%
+%%	Taken out of context, if `Patterns' is `[P1, ..., Pn]' and
+%%	`Body' is `[B1, ..., Bm]', this represents `(<P1>, ..., <Pn>) ->
+%%	<B1>, ..., <Bm>' if `Guard' is `[]', or otherwise `(<P1>, ...,
+%%	<Pn>) when <G> -> <Body>', where `G' is `<E1_1>, ..., <E1_k1>;
+%%	...; <Ej_1>, ..., <Ej_kj>', if `Guard' is a list of lists
+%%	`[[E1_1, ..., E1_k1], ..., [Ej_1, ..., Ej_kj]]'. In older
+%%	versions, `Guard' was simply a list `[E1, ..., En]' of parse
+%%	trees, which is equivalent to the new form `[[E1, ..., En]]'.
+
+clause(Patterns, Guard, Body) ->
+    Guard1 = case Guard of
+		 [] ->
+		     none;
+		 [X | _] when is_list(X) ->
+		     disjunction(conjunction_list(Guard));
+		 [_ | _] ->
+		     %% Handle older forms also.
+		     conjunction(Guard);
+		 _ ->
+		     %% This should be `none' or a syntax tree.
+		     Guard
+	     end,
+    tree(clause, #clause{patterns = Patterns, guard = Guard1,
+			 body = Body}).
+
+conjunction_list([L | Ls]) ->
+    [conjunction(L) | conjunction_list(Ls)];
+conjunction_list([]) ->
+    [].
+
+revert_clause(Node) ->
+    Pos = get_pos(Node),
+    Guard = case clause_guard(Node) of
+		none ->
+		    [];
+		E ->
+		    case type(E) of
+			disjunction ->
+			    revert_clause_disjunction(E);
+			conjunction ->
+			    %% Only the top level expression is
+			    %% unfolded here; no recursion.
+			    [conjunction_body(E)];
+			_ ->
+			    [[E]]	% a single expression
+		    end
+	    end,
+    {clause, Pos, clause_patterns(Node), Guard,
+     clause_body(Node)}.
+
+revert_clause_disjunction(D) ->
+    %% We handle conjunctions within a disjunction, but only at
+    %% the top level; no recursion.
+    [case type(E) of
+	 conjunction ->
+	     conjunction_body(E);
+	 _ ->
+	     [E]
+     end
+     || E <- disjunction_body(D)].
+
+revert_try_clause(Node) ->
+    fold_try_clause(revert_clause(Node)).
+
+fold_try_clause({clause, Pos, [P], Guard, Body}) ->
+    P1 = case type(P) of
+	     class_qualifier ->
+		 {tuple, Pos, [class_qualifier_argument(P),
+			       class_qualifier_body(P),
+			       {var, Pos, '_'}]};
+	     _ ->
+		 {tuple, Pos, [{atom, Pos, throw}, P, {var, Pos, '_'}]}
+	 end,
+    {clause, Pos, [P1], Guard, Body}.
+
+unfold_try_clauses(Cs) ->
+    [unfold_try_clause(C) || C <- Cs].
+
+unfold_try_clause({clause, Pos, [{tuple, _, [{atom,_,throw}, V, _]}],
+		   Guard, Body}) ->
+    {clause, Pos, [V], Guard, Body};
+unfold_try_clause({clause, Pos, [{tuple, _, [C, V, _]}],
+		   Guard, Body}) ->
+    {clause, Pos, [class_qualifier(C, V)], Guard, Body}.
+
+
+%% =====================================================================
+%% @spec clause_patterns(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of pattern subtrees of a <code>clause</code>
+%% node.
+%%
+%% @see clause/3
+
+clause_patterns(Node) ->
+    case unwrap(Node) of
+	{clause, _, Patterns, _, _} ->
+	    Patterns;
+	Node1 ->
+	    (data(Node1))#clause.patterns
+    end.
+
+
+%% =====================================================================
+%% @spec clause_guard(Node::syntaxTree()) -> none | syntaxTree()
+%%
+%% @doc Returns the guard subtree of a <code>clause</code> node, if
+%% any. If <code>Node</code> represents "<code>(<em>P1</em>, ...,
+%% <em>Pn</em>) when <em>Guard</em> -> <em>B1</em>, ...,
+%% <em>Bm</em></code>", <code>Guard</code> is returned. Otherwise, the
+%% result is <code>none</code>.
+%%
+%% @see clause/3
+
+clause_guard(Node) ->
+    case unwrap(Node) of
+	{clause, _, _, Guard, _} ->
+	    case Guard of
+		[] -> none;
+		[L | _] when is_list(L) ->
+		    disjunction(conjunction_list(Guard));
+		[_ | _] ->
+		    conjunction(Guard)
+	    end;
+	Node1 ->
+	    (data(Node1))#clause.guard
+    end.
+
+
+%% =====================================================================
+%% @spec clause_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Return the list of body subtrees of a <code>clause</code>
+%% node.
+%%
+%% @see clause/3
+
+clause_body(Node) ->
+    case unwrap(Node) of
+	{clause, _, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#clause.body
+    end.
+
+
+%% =====================================================================
+%% @spec disjunction(List::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract disjunction. If <code>List</code> is
+%% <code>[E1, ..., En]</code>, the result represents
+%% "<code><em>E1</em>; ...; <em>En</em></code>".
+%%
+%% @see disjunction_body/1
+%% @see conjunction/1
+
+%% type(Node) = disjunction
+%% data(Node) = [syntaxTree()]
+
+disjunction(Tests) ->
+    tree(disjunction, Tests).
+
+
+%% =====================================================================
+%% @spec disjunction_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a
+%% <code>disjunction</code> node.
+%%
+%% @see disjunction/1
+
+disjunction_body(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec conjunction(List::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract conjunction. If <code>List</code> is
+%% <code>[E1, ..., En]</code>, the result represents
+%% "<code><em>E1</em>, ..., <em>En</em></code>".
+%%
+%% @see conjunction_body/1
+%% @see disjunction/1
+
+%% type(Node) = conjunction
+%% data(Node) = [syntaxTree()]
+
+conjunction(Tests) ->
+    tree(conjunction, Tests).
+
+
+%% =====================================================================
+%% @spec conjunction_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a
+%% <code>conjunction</code> node.
+%%
+%% @see conjunction/1
+
+conjunction_body(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec catch_expr(Expr::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract catch-expression. The result represents
+%% "<code>catch <em>Expr</em></code>".
+%%
+%% @see catch_expr_body/1
+
+%% type(Node) = catch_expr
+%% data(Node) = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {'catch', Pos, Expr}
+%%
+%%	Expr = erl_parse()
+
+catch_expr(Expr) ->
+    tree(catch_expr, Expr).
+
+revert_catch_expr(Node) ->
+    Pos = get_pos(Node),
+    Expr = catch_expr_body(Node),
+    {'catch', Pos, Expr}.
+
+
+%% =====================================================================
+%% @spec catch_expr_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>catch_expr</code> node.
+%%
+%% @see catch_expr/1
+
+catch_expr_body(Node) ->
+    case unwrap(Node) of
+	{'catch', _, Expr} ->
+	    Expr;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec match_expr(Pattern::syntaxTree(), Body::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract match-expression. The result represents
+%% "<code><em>Pattern</em> = <em>Body</em></code>".
+%%
+%% @see match_expr_pattern/1
+%% @see match_expr_body/1
+
+-record(match_expr, {pattern, body}).
+
+%% type(Node) = match_expr
+%% data(Node) = #match_expr{pattern :: Pattern, body :: Body}
+%%
+%%	Pattern = Body = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {match, Pos, Pattern, Body}
+%%
+%%	Pattern = Body = erl_parse()
+
+match_expr(Pattern, Body) ->
+    tree(match_expr, #match_expr{pattern = Pattern, body = Body}).
+
+revert_match_expr(Node) ->
+    Pos = get_pos(Node),
+    Pattern = match_expr_pattern(Node),
+    Body = match_expr_body(Node),
+    {match, Pos, Pattern, Body}.
+
+
+%% =====================================================================
+%% @spec match_expr_pattern(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the pattern subtree of a <code>match_expr</code> node.
+%%
+%% @see match_expr/2
+
+match_expr_pattern(Node) ->
+    case unwrap(Node) of
+	{match, _, Pattern, _} ->
+	    Pattern;
+	Node1 ->
+	    (data(Node1))#match_expr.pattern
+    end.
+
+
+%% =====================================================================
+%% @spec match_expr_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>match_expr</code> node.
+%%
+%% @see match_expr/2
+
+match_expr_body(Node) ->
+    case unwrap(Node) of
+	{match, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#match_expr.body
+    end.
+
+
+%% =====================================================================
+%% @spec operator(Name) -> syntaxTree()
+%%	    Name = atom() | string()
+%%
+%% @doc Creates an abstract operator. The name of the operator is the
+%% character sequence represented by <code>Name</code>. This is
+%% analogous to the print name of an atom, but an operator is never
+%% written within single-quotes; e.g., the result of
+%% <code>operator('++')</code> represents "<code>++</code>" rather
+%% than "<code>'++'</code>".
+%%
+%% @see operator_name/1
+%% @see operator_literal/1
+%% @see atom/1
+
+%% type(Node) = operator
+%% data(Node) = atom()
+
+operator(Name) when is_atom(Name) ->
+    tree(operator, Name);
+operator(Name) ->
+    tree(operator, list_to_atom(Name)).
+
+
+%% =====================================================================
+%% @spec operator_name(syntaxTree()) -> atom()
+%%
+%% @doc Returns the name of an <code>operator</code> node. Note that
+%% the name is returned as an atom.
+%%
+%% @see operator/1
+
+operator_name(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec operator_literal(syntaxTree()) -> string()
+%%
+%% @doc Returns the literal string represented by an
+%% <code>operator</code> node. This is simply the operator name as a
+%% string.
+%%
+%% @see operator/1
+
+operator_literal(Node) ->
+    atom_to_list(operator_name(Node)).
+
+
+%% =====================================================================
+%% @spec infix_expr(Left::syntaxTree(), Operator::syntaxTree(),
+%%                  Right::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract infix operator expression. The result
+%% represents "<code><em>Left</em> <em>Operator</em>
+%% <em>Right</em></code>".
+%%
+%% @see infix_expr_left/1
+%% @see infix_expr_right/1
+%% @see infix_expr_operator/1
+%% @see prefix_expr/2
+
+-record(infix_expr, {operator, left, right}).
+
+%% type(Node) = infix_expr
+%% data(Node) = #infix_expr{left :: Left, operator :: Operator,
+%%		            right :: Right}
+%%
+%%	Left = Operator = Right = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {op, Pos, Operator, Left, Right}
+%%
+%%	Operator = atom()
+%%	Left = Right = erl_parse()
+
+infix_expr(Left, Operator, Right) ->
+    tree(infix_expr, #infix_expr{operator = Operator, left = Left,
+				 right = Right}).
+
+revert_infix_expr(Node) ->
+    Pos = get_pos(Node),
+    Operator = infix_expr_operator(Node),
+    Left = infix_expr_left(Node),
+    Right = infix_expr_right(Node),
+    case type(Operator) of
+	operator ->
+	    %% Note that the operator itself is not revertible out
+	    %% of context.
+	    {op, Pos, operator_name(Operator), Left, Right};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec infix_expr_left(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the left argument subtree of an
+%% <code>infix_expr</code> node.
+%%
+%% @see infix_expr/3
+
+infix_expr_left(Node) ->
+    case unwrap(Node) of
+	{op, _, _, Left, _} ->
+	    Left;
+	Node1 ->
+	    (data(Node1))#infix_expr.left
+    end.
+
+
+%% =====================================================================
+%% @spec infix_expr_operator(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the operator subtree of an <code>infix_expr</code>
+%% node.
+%%
+%% @see infix_expr/3
+
+infix_expr_operator(Node) ->
+    case unwrap(Node) of
+	{op, Pos, Operator, _, _} ->
+	    set_pos(operator(Operator), Pos);
+	Node1 ->
+	    (data(Node1))#infix_expr.operator
+    end.
+
+
+%% =====================================================================
+%% @spec infix_expr_right(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the right argument subtree of an
+%% <code>infix_expr</code> node.
+%%
+%% @see infix_expr/3
+
+infix_expr_right(Node) ->
+    case unwrap(Node) of
+	{op, _, _, _, Right} ->
+	    Right;
+	Node1 ->
+	    (data(Node1))#infix_expr.right
+    end.
+
+
+%% =====================================================================
+%% @spec prefix_expr(Operator::syntaxTree(), Argument::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract prefix operator expression. The result
+%% represents "<code><em>Operator</em> <em>Argument</em></code>".
+%%
+%% @see prefix_expr_argument/1
+%% @see prefix_expr_operator/1
+%% @see infix_expr/3
+
+-record(prefix_expr, {operator, argument}).
+
+%% type(Node) = prefix_expr
+%% data(Node) = #prefix_expr{operator :: Operator,
+%%		             argument :: Argument}
+%%
+%%	Operator = Argument = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {op, Pos, Operator, Arg}
+%%
+%%	Operator = atom()
+%%	Argument = erl_parse()
+
+prefix_expr(Operator, Argument) ->
+    tree(prefix_expr, #prefix_expr{operator = Operator,
+				   argument = Argument}).
+
+revert_prefix_expr(Node) ->
+    Pos = get_pos(Node),
+    Operator = prefix_expr_operator(Node),
+    Argument = prefix_expr_argument(Node),
+    case type(Operator) of
+	operator ->
+	    %% Note that the operator itself is not revertible out
+	    %% of context.
+	    {op, Pos, operator_name(Operator), Argument};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec prefix_expr_operator(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the operator subtree of a <code>prefix_expr</code>
+%% node.
+%%
+%% @see prefix_expr/2
+
+prefix_expr_operator(Node) ->
+    case unwrap(Node) of
+	{op, Pos, Operator, _} ->
+	    set_pos(operator(Operator), Pos);
+	Node1 ->
+	    (data(Node1))#prefix_expr.operator
+    end.
+
+
+%% =====================================================================
+%% @spec prefix_expr_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument subtree of a <code>prefix_expr</code>
+%% node.
+%%
+%% @see prefix_expr/2
+
+prefix_expr_argument(Node) ->
+    case unwrap(Node) of
+	{op, _, _, Argument} ->
+	    Argument;
+	Node1 ->
+	    (data(Node1))#prefix_expr.argument
+    end.
+
+
+%% =====================================================================
+%% @spec record_field(Name) -> syntaxTree()
+%% @equiv record_field(Name, none)
+
+record_field(Name) ->
+    record_field(Name, none).
+
+
+%% =====================================================================
+%% @spec record_field(Name::syntaxTree(), Value) -> syntaxTree()
+%%	    Value = none | syntaxTree()
+%%
+%% @doc Creates an abstract record field specification. If
+%% <code>Value</code> is <code>none</code>, the result represents
+%% simply "<code><em>Name</em></code>", otherwise it represents
+%% "<code><em>Name</em> = <em>Value</em></code>".
+%%
+%% @see record_field_name/1
+%% @see record_field_value/1
+%% @see record_expr/3
+
+-record(record_field, {name, value}).
+
+%% type(Node) = record_field
+%% data(Node) = #record_field{name :: Name, value :: Value}
+%%
+%%	Name = Value = syntaxTree()
+
+record_field(Name, Value) ->
+    tree(record_field, #record_field{name = Name, value = Value}).
+
+
+%% =====================================================================
+%% @spec record_field_name(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of a <code>record_field</code> node.
+%%
+%% @see record_field/2
+
+record_field_name(Node) ->
+    (data(Node))#record_field.name.
+
+
+%% =====================================================================
+%% @spec record_field_value(syntaxTree()) -> none | syntaxTree()
+%%
+%% @doc Returns the value subtree of a <code>record_field</code> node,
+%% if any. If <code>Node</code> represents
+%% "<code><em>Name</em></code>", <code>none</code> is
+%% returned. Otherwise, if <code>Node</code> represents
+%% "<code><em>Name</em> = <em>Value</em></code>", <code>Value</code>
+%% is returned.
+%%
+%% @see record_field/2
+
+record_field_value(Node) ->
+    (data(Node))#record_field.value.
+
+
+%% =====================================================================
+%% @spec record_index_expr(Type::syntaxTree(), Field::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract record field index expression. The result
+%% represents "<code>#<em>Type</em>.<em>Field</em></code>".
+%%
+%% <p>(Note: the function name <code>record_index/2</code> is reserved
+%% by the Erlang compiler, which is why that name could not be used
+%% for this constructor.)</p>
+%%
+%% @see record_index_expr_type/1
+%% @see record_index_expr_field/1
+%% @see record_expr/3
+
+-record(record_index_expr, {type, field}).
+
+%% type(Node) = record_index_expr
+%% data(Node) = #record_index_expr{type :: Type, field :: Field}
+%%
+%%	Type = Field = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {record_index, Pos, Type, Field}
+%%
+%%	Type = atom()
+%%	Field = erl_parse()
+
+record_index_expr(Type, Field) ->
+    tree(record_index_expr, #record_index_expr{type = Type,
+					       field = Field}).
+
+revert_record_index_expr(Node) ->
+    Pos = get_pos(Node),
+    Type = record_index_expr_type(Node),
+    Field = record_index_expr_field(Node),
+    case type(Type) of
+	atom ->
+	    {record_index, Pos, concrete(Type), Field};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec record_index_expr_type(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the type subtree of a <code>record_index_expr</code>
+%% node.
+%%
+%% @see record_index_expr/2
+
+record_index_expr_type(Node) ->
+    case unwrap(Node) of
+	{record_index, Pos, Type, _} ->
+	    set_pos(atom(Type), Pos);
+	Node1 ->
+	    (data(Node1))#record_index_expr.type
+    end.
+
+
+%% =====================================================================
+%% @spec record_index_expr_field(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the field subtree of a <code>record_index_expr</code>
+%% node.
+%%
+%% @see record_index_expr/2
+
+record_index_expr_field(Node) ->
+    case unwrap(Node) of
+	{record_index, _, _, Field} ->
+	    Field;
+	Node1 ->
+	    (data(Node1))#record_index_expr.field
+    end.
+
+
+%% =====================================================================
+%% @spec record_access(Argument, Field) -> syntaxTree()
+%% @equiv record_access(Argument, none, Field)
+
+record_access(Argument, Field) ->
+    record_access(Argument, none, Field).
+
+
+%% =====================================================================
+%% @spec record_access(Argument::syntaxTree(), Type,
+%%                     Field::syntaxTree()) -> syntaxTree()
+%%	    Type = none | syntaxTree()
+%%
+%% @doc Creates an abstract record field access expression. If
+%% <code>Type</code> is not <code>none</code>, the result represents
+%% "<code><em>Argument</em>#<em>Type</em>.<em>Field</em></code>".
+%%
+%% <p>If <code>Type</code> is <code>none</code>, the result represents
+%% "<code><em>Argument</em>.<em>Field</em></code>". This is a special
+%% form only allowed within Mnemosyne queries.</p>
+%%
+%% @see record_access/2
+%% @see record_access_argument/1
+%% @see record_access_type/1
+%% @see record_access_field/1
+%% @see record_expr/3
+%% @see query_expr/1
+
+-record(record_access, {argument, type, field}).
+
+%% type(Node) = record_access
+%% data(Node) = #record_access{argument :: Argument, type :: Type,
+%%			       field :: Field}
+%%
+%%	Argument = Field = syntaxTree()
+%%	Type = none | syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {record_field, Pos, Argument, Type, Field}
+%% {record_field, Pos, Argument, Field}
+%%
+%%	Argument = Field = erl_parse()
+%%	Type = atom()
+
+record_access(Argument, Type, Field) ->
+    tree(record_access,#record_access{argument = Argument,
+				      type = Type,
+				      field = Field}).
+
+revert_record_access(Node) ->
+    Pos = get_pos(Node),
+    Argument = record_access_argument(Node),
+    Type = record_access_type(Node),
+    Field = record_access_field(Node),
+    if Type =:= none ->
+	    {record_field, Pos, Argument, Field};
+       true ->
+	    case type(Type) of
+		atom ->
+		    {record_field, Pos,
+		     Argument, concrete(Type), Field};
+		_ ->
+		    Node
+	    end
+    end.
+
+
+%% =====================================================================
+%% @spec record_access_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument subtree of a <code>record_access</code>
+%% node.
+%%
+%% @see record_access/3
+
+record_access_argument(Node) ->
+    case unwrap(Node) of
+	{record_field, _, Argument, _} ->
+	    Argument;
+	{record_field, _, Argument, _, _} ->
+	    Argument;
+	Node1 ->
+	    (data(Node1))#record_access.argument
+    end.
+
+
+%% =====================================================================
+%% @spec record_access_type(syntaxTree()) -> none | syntaxTree()
+%%
+%% @doc Returns the type subtree of a <code>record_access</code> node,
+%% if any. If <code>Node</code> represents
+%% "<code><em>Argument</em>.<em>Field</em></code>", <code>none</code>
+%% is returned, otherwise if <code>Node</code> represents
+%% "<code><em>Argument</em>#<em>Type</em>.<em>Field</em></code>",
+%% <code>Type</code> is returned.
+%%
+%% @see record_access/3
+
+record_access_type(Node) ->
+    case unwrap(Node) of
+	{record_field, _, _, _} ->
+	    none;
+	{record_field, Pos, _, Type, _} ->
+	    set_pos(atom(Type), Pos);
+	Node1 ->
+	    (data(Node1))#record_access.type
+    end.
+
+
+%% =====================================================================
+%% @spec record_access_field(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the field subtree of a <code>record_access</code>
+%% node.
+%%
+%% @see record_access/3
+
+record_access_field(Node) ->
+    case unwrap(Node) of
+	{record_field, _, _, Field} ->
+	    Field;
+	{record_field, _, _, _, Field} ->
+	    Field;
+	Node1 ->
+	    (data(Node1))#record_access.field
+    end.
+
+
+%% =====================================================================
+%% @spec record_expr(Type, Fields) -> syntaxTree()
+%% @equiv record_expr(none, Type, Fields)
+
+record_expr(Type, Fields) ->
+    record_expr(none, Type, Fields).
+
+
+%% =====================================================================
+%% @spec record_expr(Argument, Type::syntaxTree(),
+%%                   Fields::[syntaxTree()]) -> syntaxTree()
+%%	    Argument = none | syntaxTree()
+%%
+%% @doc Creates an abstract record expression. If <code>Fields</code> is
+%% <code>[F1, ..., Fn]</code>, then if <code>Argument</code> is
+%% <code>none</code>, the result represents
+%% "<code>#<em>Type</em>{<em>F1</em>, ..., <em>Fn</em>}</code>",
+%% otherwise it represents
+%% "<code><em>Argument</em>#<em>Type</em>{<em>F1</em>, ...,
+%% <em>Fn</em>}</code>".
+%%
+%% @see record_expr/2
+%% @see record_expr_argument/1
+%% @see record_expr_fields/1
+%% @see record_expr_type/1
+%% @see record_field/2
+%% @see record_index_expr/2
+%% @see record_access/3
+
+-record(record_expr, {argument, type, fields}).
+
+%% type(Node) = record_expr
+%% data(Node) = #record_expr{argument :: Argument, type :: Type,
+%%			     fields :: Fields}
+%%
+%%	Argument = none | syntaxTree()
+%%	Type = syntaxTree
+%%	Fields = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {record, Pos, Type, Fields}
+%% {record, Pos, Argument, Type, Fields}
+%%
+%%	Argument = erl_parse()
+%%	Type = atom()
+%%	Fields = [Entry]
+%%	Entry = {record_field, Pos, Field, Value}
+%%	      | {record_field, Pos, Field}
+%%	Field = Value = erl_parse()
+
+record_expr(Argument, Type, Fields) ->
+    tree(record_expr, #record_expr{argument = Argument,
+				   type = Type, fields = Fields}).
+
+revert_record_expr(Node) ->
+    Pos = get_pos(Node),
+    Argument = record_expr_argument(Node),
+    Type = record_expr_type(Node),
+    Fields = record_expr_fields(Node),
+    case type(Type) of
+	atom ->
+	    T = concrete(Type),
+	    Fs = fold_record_fields(Fields),
+	    case Argument of
+		none ->
+		    {record, Pos, T, Fs};
+		_ ->
+		    {record, Pos, Argument, T, Fs}
+	    end;
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec record_expr_argument(syntaxTree()) -> none | syntaxTree()
+%%
+%% @doc Returns the argument subtree of a <code>record_expr</code> node,
+%% if any. If <code>Node</code> represents
+%% "<code>#<em>Type</em>{...}</code>", <code>none</code> is returned.
+%% Otherwise, if <code>Node</code> represents
+%% "<code><em>Argument</em>#<em>Type</em>{...}</code>",
+%% <code>Argument</code> is returned.
+%%
+%% @see record_expr/3
+
+record_expr_argument(Node) ->
+    case unwrap(Node) of
+	{record, _, _, _} ->
+	    none;
+	{record, _, Argument, _, _} ->
+	    Argument;
+	Node1 ->
+	    (data(Node1))#record_expr.argument
+    end.
+
+
+%% =====================================================================
+%% @spec record_expr_type(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the type subtree of a <code>record_expr</code> node.
+%%
+%% @see record_expr/3
+
+record_expr_type(Node) ->
+    case unwrap(Node) of
+	{record, Pos, Type, _} ->
+	    set_pos(atom(Type), Pos);
+	{record, Pos, _, Type, _} ->
+	    set_pos(atom(Type), Pos);
+	Node1 ->
+	    (data(Node1))#record_expr.type
+    end.
+
+
+%% =====================================================================
+%% @spec record_expr_fields(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of field subtrees of a
+%% <code>record_expr</code> node.
+%%
+%% @see record_expr/3
+
+record_expr_fields(Node) ->
+    case unwrap(Node) of
+	{record, _, _, Fields} ->
+	    unfold_record_fields(Fields);
+	{record, _, _, _, Fields} ->
+	    unfold_record_fields(Fields);
+	Node1 ->
+	    (data(Node1))#record_expr.fields
+    end.
+
+
+%% =====================================================================
+%% @spec application(Module, Function::syntaxTree(),
+%%                   Arguments::[syntaxTree()]) -> syntaxTree()
+%%	    Module = none | syntaxTree()
+%%
+%% @doc Creates an abstract function application expression. If
+%% <code>Module</code> is <code>none</code>, this is call is equivalent
+%% to <code>application(Function, Arguments)</code>, otherwise it is
+%% equivalent to <code>application(module_qualifier(Module, Function),
+%% Arguments)</code>.
+%%
+%% (This is a utility function.)
+%%
+%% @see application/2
+%% @see module_qualifier/2
+
+application(none, Name, Arguments) ->
+    application(Name, Arguments);
+application(Module, Name, Arguments) ->
+    application(module_qualifier(Module, Name), Arguments).
+
+
+%% =====================================================================
+%% @spec application(Operator::syntaxTree(),
+%%                   Arguments::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract function application expression. If
+%% <code>Arguments</code> is <code>[A1, ..., An]</code>, the result
+%% represents "<code><em>Operator</em>(<em>A1</em>, ...,
+%% <em>An</em>)</code>".
+%%
+%% @see application_operator/1
+%% @see application_arguments/1
+%% @see application/3
+
+-record(application, {operator, arguments}).
+
+%% type(Node) = application
+%% data(Node) = #application{operator :: Operator,
+%%			     arguments :: Arguments}
+%%
+%%	Operator = syntaxTree()
+%%	Arguments = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {call, Pos, Fun, Args}
+%%
+%%	Operator = erl_parse()
+%%	Arguments = [erl_parse()]
+
+application(Operator, Arguments) ->
+    tree(application, #application{operator = Operator,
+				   arguments = Arguments}).
+
+revert_application(Node) ->
+    Pos = get_pos(Node),
+    Operator = application_operator(Node),
+    Arguments = application_arguments(Node),
+    {call, Pos, Operator, Arguments}.
+
+
+%% =====================================================================
+%% @spec application_operator(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the operator subtree of an <code>application</code>
+%% node.
+%%
+%% <p>Note: if <code>Node</code> represents
+%% "<code><em>M</em>:<em>F</em>(...)</code>", then the result is the
+%% subtree representing "<code><em>M</em>:<em>F</em></code>".</p>
+%%
+%% @see application/2
+%% @see module_qualifier/2
+
+application_operator(Node) ->
+    case unwrap(Node) of
+	{call, _, Operator, _} ->
+	    Operator;
+	Node1 ->
+	    (data(Node1))#application.operator
+    end.
+
+
+%% =====================================================================
+%% @spec application_arguments(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of argument subtrees of an
+%% <code>application</code> node.
+%%
+%% @see application/2
+
+application_arguments(Node) ->
+    case unwrap(Node) of
+	{call, _, _, Arguments} ->
+	    Arguments;
+	Node1 ->
+	    (data(Node1))#application.arguments
+    end.
+
+
+%% =====================================================================
+%% @spec list_comp(Template::syntaxTree(), Body::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract list comprehension. If <code>Body</code> is
+%% <code>[E1, ..., En]</code>, the result represents
+%% "<code>[<em>Template</em> || <em>E1</em>, ..., <em>En</em>]</code>".
+%%
+%% @see list_comp_template/1
+%% @see list_comp_body/1
+%% @see generator/2
+
+-record(list_comp, {template, body}).
+
+%% type(Node) = list_comp
+%% data(Node) = #list_comp{template :: Template, body :: Body}
+%%
+%%	Template = Node = syntaxTree()
+%%	Body = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {lc, Pos, Template, Body}
+%%
+%%	Template = erl_parse()
+%%	Body = [erl_parse()] \ []
+
+list_comp(Template, Body) ->
+    tree(list_comp, #list_comp{template = Template, body = Body}).
+
+revert_list_comp(Node) ->
+    Pos = get_pos(Node),
+    Template = list_comp_template(Node),
+    Body = list_comp_body(Node),
+    {lc, Pos, Template, Body}.
+
+
+%% =====================================================================
+%% @spec list_comp_template(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the template subtree of a <code>list_comp</code> node.
+%%
+%% @see list_comp/2
+
+list_comp_template(Node) ->
+    case unwrap(Node) of
+	{lc, _, Template, _} ->
+	    Template;
+	Node1 ->
+	    (data(Node1))#list_comp.template
+    end.
+
+
+%% =====================================================================
+%% @spec list_comp_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a <code>list_comp</code>
+%% node.
+%%
+%% @see list_comp/2
+
+list_comp_body(Node) ->
+    case unwrap(Node) of
+	{lc, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#list_comp.body
+    end.
+
+%% =====================================================================
+%% @spec binary_comp(Template::syntaxTree(), Body::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract binary comprehension. If <code>Body</code> is
+%% <code>[E1, ..., En]</code>, the result represents
+%% "<code>&lt;&lt;<em>Template</em> || <em>E1</em>, ..., <em>En</em>&gt;&gt;</code>".
+%%
+%% @see binary_comp_template/1
+%% @see binary_comp_body/1
+%% @see generator/2
+
+-record(binary_comp, {template, body}).
+
+%% type(Node) = binary_comp
+%% data(Node) = #binary_comp{template :: Template, body :: Body}
+%%
+%%	Template = Node = syntaxTree()
+%%	Body = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {bc, Pos, Template, Body}
+%%
+%%	Template = erl_parse()
+%%	Body = [erl_parse()] \ []
+
+binary_comp(Template, Body) ->
+    tree(binary_comp, #binary_comp{template = Template, body = Body}).
+
+revert_binary_comp(Node) ->
+    Pos = get_pos(Node),
+    Template = binary_comp_template(Node),
+    Body = binary_comp_body(Node),
+    {bc, Pos, Template, Body}.
+
+
+%% =====================================================================
+%% @spec binary_comp_template(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the template subtree of a <code>binary_comp</code> node.
+%%
+%% @see binary_comp/2
+
+binary_comp_template(Node) ->
+    case unwrap(Node) of
+	{bc, _, Template, _} ->
+	    Template;
+	Node1 ->
+	    (data(Node1))#binary_comp.template
+    end.
+
+
+%% =====================================================================
+%% @spec binary_comp_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a <code>binary_comp</code>
+%% node.
+%%
+%% @see binary_comp/2
+
+binary_comp_body(Node) ->
+    case unwrap(Node) of
+	{bc, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#binary_comp.body
+    end.
+
+
+%% =====================================================================
+%% @spec query_expr(Body::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract Mnemosyne query expression. The result
+%% represents "<code>query <em>Body</em> end</code>".
+%%
+%% @see query_expr_body/1
+%% @see record_access/2
+%% @see rule/2
+
+%% type(Node) = query_expr
+%% data(Node) = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {'query', Pos, Body}
+%%
+%%	Body = erl_parse()
+
+query_expr(Body) ->
+    tree(query_expr, Body).
+
+revert_query_expr(Node) ->
+    Pos = get_pos(Node),
+    Body = list_comp_body(Node),
+    {'query', Pos, Body}.
+
+
+%% =====================================================================
+%% @spec query_expr_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>query_expr</code> node.
+%%
+%% @see query_expr/1
+
+query_expr_body(Node) ->
+    case unwrap(Node) of
+	{'query', _, Body} ->
+	    Body;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec rule(Name::syntaxTree(), Clauses::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract Mnemosyne rule. If <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code>, the results represents
+%% "<code><em>Name</em> <em>C1</em>; ...; <em>Name</em>
+%% <em>Cn</em>.</code>". More exactly, if each <code>Ci</code>
+%% represents "<code>(<em>Pi1</em>, ..., <em>Pim</em>) <em>Gi</em> ->
+%% <em>Bi</em></code>", then the result represents
+%% "<code><em>Name</em>(<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> :-
+%% <em>B1</em>; ...; <em>Name</em>(<em>Pn1</em>, ..., <em>Pnm</em>)
+%% <em>Gn</em> :- <em>Bn</em>.</code>". Rules are source code forms.
+%%
+%% @see rule_name/1
+%% @see rule_clauses/1
+%% @see rule_arity/1
+%% @see is_form/1
+%% @see function/2
+
+-record(rule, {name, clauses}).
+
+%% type(Node) = rule
+%% data(Node) = #rule{name :: Name, clauses :: Clauses}
+%%
+%%	Name = syntaxTree()
+%%	Clauses = [syntaxTree()]
+%%
+%%	(See `function' for notes on why the arity is not stored.)
+%%
+%% `erl_parse' representation:
+%%
+%% {rule, Pos, Name, Arity, Clauses}
+%%
+%%	Name = atom()
+%%	Arity = integer()
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	where the number of patterns in each clause should be equal to
+%%	the integer `Arity'; see `clause' for documentation on
+%%	`erl_parse' clauses.
+
+rule(Name, Clauses) ->
+    tree(rule, #rule{name = Name, clauses = Clauses}).
+
+revert_rule(Node) ->
+    Name = rule_name(Node),
+    Clauses = [revert_clause(C) || C <- rule_clauses(Node)],
+    Pos = get_pos(Node),
+    case type(Name) of
+	atom ->
+	    A = rule_arity(Node),
+	    {rule, Pos, concrete(Name), A, Clauses};
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec rule_name(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of a <code>rule</code> node.
+%%
+%% @see rule/2
+
+rule_name(Node) ->
+    case unwrap(Node) of
+	{rule, Pos, Name, _, _} ->
+	    set_pos(atom(Name), Pos);
+	Node1 ->
+	    (data(Node1))#rule.name
+    end.
+
+%% =====================================================================
+%% @spec rule_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of a <code>rule</code> node.
+%%
+%% @see rule/2
+
+rule_clauses(Node) ->
+    case unwrap(Node) of
+	{rule, _, _, _, Clauses} ->
+	    Clauses;
+	Node1 ->
+	    (data(Node1))#rule.clauses
+    end.
+
+%% =====================================================================
+%% @spec rule_arity(Node::syntaxTree()) -> integer()
+%%
+%% @doc Returns the arity of a <code>rule</code> node. The result is the
+%% number of parameter patterns in the first clause of the rule;
+%% subsequent clauses are ignored.
+%%
+%% <p>An exception is thrown if <code>rule_clauses(Node)</code> returns
+%% an empty list, or if the first element of that list is not a syntax
+%% tree <code>C</code> of type <code>clause</code> such that
+%% <code>clause_patterns(C)</code> is a nonempty list.</p>
+%%
+%% @see rule/2
+%% @see rule_clauses/1
+%% @see clause/3
+%% @see clause_patterns/1
+
+rule_arity(Node) ->
+    %% Note that this never accesses the arity field of
+    %% `erl_parse' rule nodes.
+    length(clause_patterns(hd(rule_clauses(Node)))).
+
+
+%% =====================================================================
+%% @spec generator(Pattern::syntaxTree(), Body::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract generator. The result represents
+%% "<code><em>Pattern</em> &lt;- <em>Body</em></code>".
+%%
+%% @see generator_pattern/1
+%% @see generator_body/1
+%% @see list_comp/2
+%% @see binary_comp/2
+
+-record(generator, {pattern, body}).
+
+%% type(Node) = generator
+%% data(Node) = #generator{pattern :: Pattern, body :: Body}
+%%
+%%	Pattern = Argument = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {generate, Pos, Pattern, Body}
+%%
+%%	Pattern = Body = erl_parse()
+
+generator(Pattern, Body) ->
+    tree(generator, #generator{pattern = Pattern, body = Body}).
+
+revert_generator(Node) ->
+    Pos = get_pos(Node),
+    Pattern = generator_pattern(Node),
+    Body = generator_body(Node),
+    {generate, Pos, Pattern, Body}.
+
+
+%% =====================================================================
+%% @spec generator_pattern(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the pattern subtree of a <code>generator</code> node.
+%%
+%% @see generator/2
+
+generator_pattern(Node) ->
+    case unwrap(Node) of
+	{generate, _, Pattern, _} ->
+	    Pattern;
+	Node1 ->
+	    (data(Node1))#generator.pattern
+    end.
+
+
+%% =====================================================================
+%% @spec generator_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>generator</code> node.
+%%
+%% @see generator/2
+
+generator_body(Node) ->
+    case unwrap(Node) of
+	{generate, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#generator.body
+    end.
+
+
+%% =====================================================================
+%% @spec binary_generator(Pattern::syntaxTree(), Body::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract binary_generator. The result represents
+%% "<code><em>Pattern</em> &lt;- <em>Body</em></code>".
+%%
+%% @see binary_generator_pattern/1
+%% @see binary_generator_body/1
+%% @see list_comp/2
+%% @see binary_comp/2
+
+-record(binary_generator, {pattern, body}).
+
+%% type(Node) = binary_generator
+%% data(Node) = #binary_generator{pattern :: Pattern, body :: Body}
+%%
+%%	Pattern = Argument = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {b_generate, Pos, Pattern, Body}
+%%
+%%	Pattern = Body = erl_parse()
+
+binary_generator(Pattern, Body) ->
+    tree(binary_generator, #binary_generator{pattern = Pattern, body = Body}).
+
+revert_binary_generator(Node) ->
+    Pos = get_pos(Node),
+    Pattern = binary_generator_pattern(Node),
+    Body = binary_generator_body(Node),
+    {b_generate, Pos, Pattern, Body}.
+
+
+%% =====================================================================
+%% @spec binary_generator_pattern(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the pattern subtree of a <code>generator</code> node.
+%%
+%% @see binary_generator/2
+
+binary_generator_pattern(Node) ->
+    case unwrap(Node) of
+	{b_generate, _, Pattern, _} ->
+	    Pattern;
+	Node1 ->
+	    (data(Node1))#binary_generator.pattern
+    end.
+
+
+%% =====================================================================
+%% @spec binary_generator_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>generator</code> node.
+%%
+%% @see binary_generator/2
+
+binary_generator_body(Node) ->
+    case unwrap(Node) of
+	{b_generate, _, _, Body} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#binary_generator.body
+    end.
+
+%% =====================================================================
+%% @spec block_expr(Body::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract block expression. If <code>Body</code> is
+%% <code>[B1, ..., Bn]</code>, the result represents "<code>begin
+%% <em>B1</em>, ..., <em>Bn</em> end</code>".
+%%
+%% @see block_expr_body/1
+
+%% type(Node) = block_expr
+%% data(Node) = Body
+%%
+%%	Body = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {block, Pos, Body}
+%%
+%%	    Body = [erl_parse()] \ []
+
+block_expr(Body) ->
+    tree(block_expr, Body).
+
+revert_block_expr(Node) ->
+    Pos = get_pos(Node),
+    Body = block_expr_body(Node),
+    {block, Pos, Body}.
+
+
+%% =====================================================================
+%% @spec block_expr_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a <code>block_expr</code>
+%% node.
+%%
+%% @see block_expr/1
+
+block_expr_body(Node) ->
+    case unwrap(Node) of
+	{block, _, Body} ->
+	    Body;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec if_expr(Clauses::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract if-expression. If <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code>, the result represents "<code>if
+%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
+%% <code>Ci</code> represents "<code>() <em>Gi</em> ->
+%% <em>Bi</em></code>", then the result represents "<code>if
+%% <em>G1</em> -> <em>B1</em>; ...; <em>Gn</em> -> <em>Bn</em>
+%% end</code>".
+%%
+%% @see if_expr_clauses/1
+%% @see clause/3
+%% @see case_expr/2
+
+%% type(Node) = if_expr
+%% data(Node) = Clauses
+%%
+%%	Clauses = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {'if', Pos, Clauses}
+%%
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+if_expr(Clauses) ->
+    tree(if_expr, Clauses).
+
+revert_if_expr(Node) ->
+    Pos = get_pos(Node),
+    Clauses = [revert_clause(C) || C <- if_expr_clauses(Node)],
+    {'if', Pos, Clauses}.
+
+
+%% =====================================================================
+%% @spec if_expr_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of an <code>if_expr</code>
+%% node.
+%%
+%% @see if_expr/1
+
+if_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'if', _, Clauses} ->
+	    Clauses;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec case_expr(Argument::syntaxTree(), Clauses::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract case-expression. If <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code>, the result represents "<code>case
+%% <em>Argument</em> of <em>C1</em>; ...; <em>Cn</em> end</code>". More
+%% exactly, if each <code>Ci</code> represents "<code>(<em>Pi</em>)
+%% <em>Gi</em> -> <em>Bi</em></code>", then the result represents
+%% "<code>case <em>Argument</em> of <em>P1</em> <em>G1</em> ->
+%% <em>B1</em>; ...; <em>Pn</em> <em>Gn</em> -> <em>Bn</em> end</code>".
+%%
+%% @see case_expr_clauses/1
+%% @see case_expr_argument/1
+%% @see clause/3
+%% @see if_expr/1
+%% @see cond_expr/1
+
+-record(case_expr, {argument, clauses}).
+
+%% type(Node) = case_expr
+%% data(Node) = #case_expr{argument :: Argument,
+%%			   clauses :: Clauses}
+%%
+%%	Argument = syntaxTree()
+%%	Clauses = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {'case', Pos, Argument, Clauses}
+%%
+%%	Argument = erl_parse()
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+case_expr(Argument, Clauses) ->
+    tree(case_expr, #case_expr{argument = Argument,
+			       clauses = Clauses}).
+
+revert_case_expr(Node) ->
+    Pos = get_pos(Node),
+    Argument = case_expr_argument(Node),
+    Clauses = [revert_clause(C) || C <- case_expr_clauses(Node)],
+    {'case', Pos, Argument, Clauses}.
+
+
+%% =====================================================================
+%% @spec case_expr_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument subtree of a <code>case_expr</code> node.
+%%
+%% @see case_expr/2
+
+case_expr_argument(Node) ->
+    case unwrap(Node) of
+	{'case', _, Argument, _} ->
+	    Argument;
+	Node1 ->
+	    (data(Node1))#case_expr.argument
+    end.
+
+
+%% =====================================================================
+%% @spec case_expr_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of a <code>case_expr</code>
+%% node.
+%%
+%% @see case_expr/2
+
+case_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'case', _, _, Clauses} ->
+	    Clauses;
+	Node1 ->
+	    (data(Node1))#case_expr.clauses
+    end.
+
+
+%% =====================================================================
+%% @spec cond_expr(Clauses::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract cond-expression. If <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code>, the result represents "<code>cond
+%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
+%% <code>Ci</code> represents "<code>() <em>Ei</em> ->
+%% <em>Bi</em></code>", then the result represents "<code>cond
+%% <em>E1</em> -> <em>B1</em>; ...; <em>En</em> -> <em>Bn</em>
+%% end</code>".
+%%
+%% @see cond_expr_clauses/1
+%% @see clause/3
+%% @see case_expr/2
+
+%% type(Node) = cond_expr
+%% data(Node) = Clauses
+%%
+%%	Clauses = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {'cond', Pos, Clauses}
+%%
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+cond_expr(Clauses) ->
+    tree(cond_expr, Clauses).
+
+revert_cond_expr(Node) ->
+    Pos = get_pos(Node),
+    Clauses = [revert_clause(C) || C <- cond_expr_clauses(Node)],
+    {'cond', Pos, Clauses}.
+
+
+%% =====================================================================
+%% @spec cond_expr_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of a <code>cond_expr</code>
+%% node.
+%%
+%% @see cond_expr/1
+
+cond_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'cond', _, Clauses} ->
+	    Clauses;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec receive_expr(Clauses) -> syntaxTree()
+%% @equiv receive_expr(Clauses, none, [])
+
+receive_expr(Clauses) ->
+    receive_expr(Clauses, none, []).
+
+
+%% =====================================================================
+%% @spec receive_expr(Clauses::[syntaxTree()], Timeout,
+%%                    Action::[syntaxTree()]) -> syntaxTree()
+%%	    Timeout = none | syntaxTree()
+%%
+%% @doc Creates an abstract receive-expression. If <code>Timeout</code>
+%% is <code>none</code>, the result represents "<code>receive
+%% <em>C1</em>; ...; <em>Cn</em> end</code>" (the <code>Action</code>
+%% argument is ignored). Otherwise, if <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code> and <code>Action</code> is <code>[A1, ...,
+%% Am]</code>, the result represents "<code>receive <em>C1</em>; ...;
+%% <em>Cn</em> after <em>Timeout</em> -> <em>A1</em>, ..., <em>Am</em>
+%% end</code>". More exactly, if each <code>Ci</code> represents
+%% "<code>(<em>Pi</em>) <em>Gi</em> -> <em>Bi</em></code>", then the
+%% result represents "<code>receive <em>P1</em> <em>G1</em> ->
+%% <em>B1</em>; ...; <em>Pn</em> <em>Gn</em> -> <em>Bn</em> ...
+%% end</code>".
+%%
+%% <p>Note that in Erlang, a receive-expression must have at least one
+%% clause if no timeout part is specified.</p>
+%%
+%% @see receive_expr_clauses/1
+%% @see receive_expr_timeout/1
+%% @see receive_expr_action/1
+%% @see receive_expr/1
+%% @see clause/3
+%% @see case_expr/2
+
+-record(receive_expr, {clauses, timeout, action}).
+
+%% type(Node) = receive_expr
+%% data(Node) = #receive_expr{clauses :: Clauses,
+%%			      timeout :: Timeout,
+%%			      action :: Action}
+%%
+%%	Clauses = [syntaxTree()]
+%%	Timeout = none | syntaxTree()
+%%	Action = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {'receive', Pos, Clauses}
+%% {'receive', Pos, Clauses, Timeout, Action}
+%%
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%	Timeout = erl_parse()
+%%	Action = [erl_parse()] \ []
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+receive_expr(Clauses, Timeout, Action) ->
+    %% If `Timeout' is `none', we always replace the actual
+    %% `Action' argument with an empty list, since
+    %% `receive_expr_action' should in that case return the empty
+    %% list regardless.
+    Action1 = case Timeout of
+		  none -> [];
+		  _ -> Action
+	      end,
+    tree(receive_expr, #receive_expr{clauses = Clauses,
+				     timeout = Timeout,
+				     action = Action1}).
+
+revert_receive_expr(Node) ->
+    Pos = get_pos(Node),
+    Clauses = [revert_clause(C) || C <- receive_expr_clauses(Node)],
+    Timeout = receive_expr_timeout(Node),
+    Action = receive_expr_action(Node),
+    case Timeout of
+	none ->
+	    {'receive', Pos, Clauses};
+	_ ->
+	    {'receive', Pos, Clauses, Timeout, Action}
+    end.
+
+
+%% =====================================================================
+%% @spec receive_expr_clauses(syntaxTree()) -> [syntaxTree()]
+%%	     type(Node) = receive_expr
+%%
+%% @doc Returns the list of clause subtrees of a
+%% <code>receive_expr</code> node.
+%%
+%% @see receive_expr/3
+
+receive_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'receive', _, Clauses} ->
+	    Clauses;
+	{'receive', _, Clauses, _, _} ->
+	    Clauses;
+	Node1 ->
+	    (data(Node1))#receive_expr.clauses
+    end.
+
+
+%% =====================================================================
+%% @spec receive_expr_timeout(Node::syntaxTree()) -> Timeout
+%%	     Timeout = none | syntaxTree()
+%%
+%% @doc Returns the timeout subtree of a <code>receive_expr</code> node,
+%% if any. If <code>Node</code> represents "<code>receive <em>C1</em>;
+%% ...; <em>Cn</em> end</code>", <code>none</code> is returned.
+%% Otherwise, if <code>Node</code> represents "<code>receive
+%% <em>C1</em>; ...; <em>Cn</em> after <em>Timeout</em> -> ... end</code>",
+%% <code>Timeout</code> is returned.
+%%
+%% @see receive_expr/3
+
+receive_expr_timeout(Node) ->
+    case unwrap(Node) of
+	{'receive', _, _} ->
+	    none;
+	{'receive', _, _, Timeout, _} ->
+	    Timeout;
+	Node1 ->
+	    (data(Node1))#receive_expr.timeout
+    end.
+
+
+%% =====================================================================
+%% @spec receive_expr_action(Node::syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of action body subtrees of a
+%% <code>receive_expr</code> node. If <code>Node</code> represents
+%% "<code>receive <em>C1</em>; ...; <em>Cn</em> end</code>", this is the
+%% empty list.
+%%
+%% @see receive_expr/3
+
+receive_expr_action(Node) ->
+    case unwrap(Node) of
+	{'receive', _, _} ->
+	    [];
+	{'receive', _, _, _, Action} ->
+	    Action;
+	Node1 ->
+	    (data(Node1))#receive_expr.action
+    end.
+
+
+%% =====================================================================
+%% @spec try_expr(Body::syntaxTree(), Handlers::[syntaxTree()]) ->
+%%           syntaxTree()
+%% @equiv try_expr(Body, [], Handlers)
+
+try_expr(Body, Handlers) ->
+    try_expr(Body, [], Handlers).
+
+
+%% =====================================================================
+%% @spec try_expr(Body::syntaxTree(), Clauses::[syntaxTree()],
+%%           Handlers::[syntaxTree()]) -> syntaxTree()
+%% @equiv try_expr(Body, Clauses, Handlers, [])
+
+try_expr(Body, Clauses, Handlers) ->
+    try_expr(Body, Clauses, Handlers, []).
+
+
+%% =====================================================================
+%% @spec try_after_expr(Body::syntaxTree(), After::[syntaxTree()]) ->
+%%           syntaxTree()
+%% @equiv try_expr(Body, [], [], After)
+
+try_after_expr(Body, After) ->
+    try_expr(Body, [], [], After).
+
+
+%% =====================================================================
+%% @spec try_expr(Body::[syntaxTree()], Clauses::[syntaxTree()],
+%%                Handlers::[syntaxTree()], After::[syntaxTree()]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract try-expression. If <code>Body</code> is
+%% <code>[B1, ..., Bn]</code>, <code>Clauses</code> is <code>[C1, ...,
+%% Cj]</code>, <code>Handlers</code> is <code>[H1, ..., Hk]</code>, and
+%% <code>After</code> is <code>[A1, ..., Am]</code>, the result
+%% represents "<code>try <em>B1</em>, ..., <em>Bn</em> of <em>C1</em>;
+%% ...; <em>Cj</em> catch <em>H1</em>; ...; <em>Hk</em> after
+%% <em>A1</em>, ..., <em>Am</em> end</code>". More exactly, if each
+%% <code>Ci</code> represents "<code>(<em>CPi</em>) <em>CGi</em> ->
+%% <em>CBi</em></code>", and each <code>Hi</code> represents
+%% "<code>(<em>HPi</em>) <em>HGi</em> -> <em>HBi</em></code>", then the
+%% result represents "<code>try <em>B1</em>, ..., <em>Bn</em> of
+%% <em>CP1</em> <em>CG1</em> -> <em>CB1</em>; ...; <em>CPj</em>
+%% <em>CGj</em> -> <em>CBj</em> catch <em>HP1</em> <em>HG1</em> ->
+%% <em>HB1</em>; ...; <em>HPk</em> <em>HGk</em> -> <em>HBk</em> after
+%% <em>A1</em>, ..., <em>Am</em> end</code>"; cf.
+%% <code>case_expr/2</code>. If <code>Clauses</code> is the empty list,
+%% the <code>of ...</code> section is left out. If <code>After</code> is
+%% the empty list, the <code>after ...</code> section is left out. If
+%% <code>Handlers</code> is the empty list, and <code>After</code> is
+%% nonempty, the <code>catch ...</code> section is left out.
+%%
+%% @see try_expr_body/1
+%% @see try_expr_clauses/1
+%% @see try_expr_handlers/1
+%% @see try_expr_after/1
+%% @see try_expr/2
+%% @see try_expr/3
+%% @see try_after_expr/2
+%% @see clause/3
+%% @see class_qualifier/2
+%% @see case_expr/2
+
+-record(try_expr, {body, clauses, handlers, 'after'}).
+
+%% type(Node) = try_expr
+%% data(Node) = #try_expr{body :: Body,
+%%			  clauses :: Clauses,
+%%			  handlers :: Clauses,
+%%			  after :: Body}
+%%
+%%	Body = syntaxTree()
+%%	Clauses = [syntaxTree()]
+%%
+%% `erl_parse' representation:
+%%
+%% {'try', Pos, Body, Clauses, Handlers, After}
+%%
+%%	Body = [erl_parse()]
+%%	Clauses = [Clause]
+%%	Handlers = [Clause] \ []
+%%	Clause = {clause, ...}
+%%	After = [erl_parse()]
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+try_expr(Body, Clauses, Handlers, After) ->
+    tree(try_expr, #try_expr{body = Body,
+			     clauses = Clauses,
+			     handlers = Handlers,
+			     'after' = After}).
+
+revert_try_expr(Node) ->
+    Pos = get_pos(Node),
+    Body = try_expr_body(Node),
+    Clauses = [revert_clause(C) || C <- try_expr_clauses(Node)],
+    Handlers = [revert_try_clause(C) || C <- try_expr_handlers(Node)],
+    After = try_expr_after(Node),
+    {'try', Pos, Body, Clauses, Handlers, After}.
+
+
+%% =====================================================================
+%% @spec try_expr_body(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of body subtrees of a <code>try_expr</code>
+%% node.
+%%
+%% @see try_expr/4
+
+try_expr_body(Node) ->
+    case unwrap(Node) of
+	{'try', _, Body, _, _, _} ->
+	    Body;
+	Node1 ->
+	    (data(Node1))#try_expr.body
+    end.
+
+
+%% =====================================================================
+%% @spec try_expr_clauses(Node::syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of case-clause subtrees of a
+%% <code>try_expr</code> node. If <code>Node</code> represents
+%% "<code>try <em>Body</em> catch <em>H1</em>; ...; <em>Hn</em>
+%% end</code>", the result is the empty list.
+%%
+%% @see try_expr/4
+
+try_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'try', _, _, Clauses, _, _} ->
+	    Clauses;
+	Node1 ->
+	    (data(Node1))#try_expr.clauses
+    end.
+
+
+%% =====================================================================
+%% @spec try_expr_handlers(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of handler-clause subtrees of a
+%% <code>try_expr</code> node.
+%%
+%% @see try_expr/4
+
+try_expr_handlers(Node) ->
+    case unwrap(Node) of
+	{'try', _, _, _, Handlers, _} ->
+	    unfold_try_clauses(Handlers);
+	Node1 ->
+	    (data(Node1))#try_expr.handlers
+    end.
+
+
+%% =====================================================================
+%% @spec try_expr_after(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of "after" subtrees of a <code>try_expr</code>
+%% node.
+%%
+%% @see try_expr/4
+
+try_expr_after(Node) ->
+    case unwrap(Node) of
+	{'try', _, _, _, _, After} ->
+	    After;
+	Node1 ->
+	    (data(Node1))#try_expr.'after'
+    end.
+
+
+%% =====================================================================
+%% @spec class_qualifier(Class::syntaxTree(), Body::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract class qualifier. The result represents
+%% "<code><em>Class</em>:<em>Body</em></code>".
+%%
+%% @see class_qualifier_argument/1
+%% @see class_qualifier_body/1
+%% @see try_expr/4
+
+-record(class_qualifier, {class, body}).
+
+%% type(Node) = class_qualifier
+%% data(Node) = #class_qualifier{class :: Class, body :: Body}
+%%
+%%	Class = Body = syntaxTree()
+
+class_qualifier(Class, Body) ->
+    tree(class_qualifier,
+	 #class_qualifier{class = Class, body = Body}).
+
+
+%% =====================================================================
+%% @spec class_qualifier_argument(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the argument (the class) subtree of a
+%% <code>class_qualifier</code> node.
+%%
+%% @see class_qualifier/2
+
+class_qualifier_argument(Node) ->
+    (data(Node))#class_qualifier.class.
+
+
+%% =====================================================================
+%% @spec class_qualifier_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>class_qualifier</code> node.
+%%
+%% @see class_qualifier/2
+
+class_qualifier_body(Node) ->
+    (data(Node))#class_qualifier.body.
+
+
+%% =====================================================================
+%% @spec implicit_fun(Name::syntaxTree(), Arity::syntaxTree()) ->
+%%           syntaxTree()
+%%
+%% @doc Creates an abstract "implicit fun" expression. If
+%% <code>Arity</code> is <code>none</code>, this is equivalent to
+%% <code>implicit_fun(Name)</code>, otherwise it is equivalent to
+%% <code>implicit_fun(arity_qualifier(Name, Arity))</code>.
+%%
+%% (This is a utility function.)
+%%
+%% @see implicit_fun/1
+%% @see implicit_fun/3
+
+implicit_fun(Name, none) ->
+    implicit_fun(Name);
+implicit_fun(Name, Arity) ->
+    implicit_fun(arity_qualifier(Name, Arity)).
+
+
+%% =====================================================================
+%% @spec implicit_fun(Module::syntaxTree(), Name::syntaxTree(),
+%%                    Arity::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract module-qualified "implicit fun" expression.
+%% If <code>Module</code> is <code>none</code>, this is equivalent to
+%% <code>implicit_fun(Name, Arity)</code>, otherwise it is equivalent to
+%% <code>implicit_fun(module_qualifier(Module, arity_qualifier(Name,
+%% Arity))</code>.
+%%
+%% (This is a utility function.)
+%%
+%% @see implicit_fun/1
+%% @see implicit_fun/2
+
+implicit_fun(none, Name, Arity) ->
+    implicit_fun(Name, Arity);
+implicit_fun(Module, Name, Arity) ->
+    implicit_fun(module_qualifier(Module, arity_qualifier(Name, Arity))).
+
+
+%% =====================================================================
+%% @spec implicit_fun(Name::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract "implicit fun" expression. The result
+%% represents "<code>fun <em>Name</em></code>". <code>Name</code> should
+%% represent either <code><em>F</em>/<em>A</em></code> or
+%% <code><em>M</em>:<em>F</em>/<em>A</em></code>
+%%
+%% @see implicit_fun_name/1
+%% @see implicit_fun/2
+%% @see implicit_fun/3
+%% @see arity_qualifier/2
+%% @see module_qualifier/2
+
+%% type(Node) = implicit_fun
+%% data(Node) = syntaxTree()
+%%
+%% `erl_parse' representation:
+%%
+%% {'fun', Pos, {function, Name, Arity}}
+%% {'fun', Pos, {function, Module, Name, Arity}}
+%%
+%%	Module = atom()
+%%	Name = atom()
+%%	Arity = integer()
+
+implicit_fun(Name) ->
+    tree(implicit_fun, Name).
+
+revert_implicit_fun(Node) ->
+    Pos = get_pos(Node),
+    Name = implicit_fun_name(Node),
+    case type(Name) of
+	arity_qualifier ->
+	    F = arity_qualifier_body(Name),
+	    A = arity_qualifier_argument(Name),
+	    case {type(F), type(A)} of
+		{atom, integer} ->
+		    {'fun', Pos,
+		     {function, concrete(F), concrete(A)}};
+		_ ->
+		    Node
+	    end;
+	module_qualifier ->
+	    M = module_qualifier_argument(Name),
+	    Name1 = module_qualifier_body(Name),
+	    F = arity_qualifier_body(Name1),
+	    A = arity_qualifier_argument(Name1),
+	    case {type(M), type(F), type(A)} of
+		{atom, atom, integer} ->
+		    {'fun', Pos,
+		     {function, concrete(M), concrete(F), concrete(A)}};
+		_ ->
+		    Node
+	    end;
+	_ ->
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec implicit_fun_name(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of an <code>implicit_fun</code> node.
+%%
+%% <p>Note: if <code>Node</code> represents "<code>fun
+%% <em>N</em>/<em>A</em></code>" or "<code>fun
+%% <em>M</em>:<em>N</em>/<em>A</em></code>", then the result is the
+%% subtree representing "<code><em>N</em>/<em>A</em></code>" or
+%% "<code><em>M</em>:<em>N</em>/<em>A</em></code>", respectively.</p>
+%%
+%% @see implicit_fun/1
+%% @see arity_qualifier/2
+%% @see module_qualifier/2
+
+implicit_fun_name(Node) ->
+    case unwrap(Node) of
+	{'fun', Pos, {function, Atom, Arity}} ->
+	    arity_qualifier(set_pos(atom(Atom), Pos),
+			    set_pos(integer(Arity), Pos));
+	{'fun', Pos, {function, Module, Atom, Arity}} ->
+	    module_qualifier(set_pos(atom(Module), Pos),
+			     arity_qualifier(
+			       set_pos(atom(Atom), Pos),
+			       set_pos(integer(Arity), Pos)));
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec fun_expr(Clauses::[syntaxTree()]) -> syntaxTree()
+%%
+%% @doc Creates an abstract fun-expression. If <code>Clauses</code> is
+%% <code>[C1, ..., Cn]</code>, the result represents "<code>fun
+%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
+%% <code>Ci</code> represents "<code>(<em>Pi1</em>, ..., <em>Pim</em>)
+%% <em>Gi</em> -> <em>Bi</em></code>", then the result represents
+%% "<code>fun (<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> ->
+%% <em>B1</em>; ...; (<em>Pn1</em>, ..., <em>Pnm</em>) <em>Gn</em> ->
+%% <em>Bn</em> end</code>".
+%%
+%% @see fun_expr_clauses/1
+%% @see fun_expr_arity/1
+
+%% type(Node) = fun_expr
+%% data(Node) = Clauses
+%%
+%%	Clauses = [syntaxTree()]
+%%
+%%	(See `function' for notes; e.g. why the arity is not stored.)
+%%
+%% `erl_parse' representation:
+%%
+%% {'fun', Pos, {clauses, Clauses}}
+%%
+%%	Clauses = [Clause] \ []
+%%	Clause = {clause, ...}
+%%
+%%	See `clause' for documentation on `erl_parse' clauses.
+
+fun_expr(Clauses) ->
+    tree(fun_expr, Clauses).
+
+revert_fun_expr(Node) ->
+    Clauses = [revert_clause(C) || C <- fun_expr_clauses(Node)],
+    Pos = get_pos(Node),
+    {'fun', Pos, {clauses, Clauses}}.
+
+
+%% =====================================================================
+%% @spec fun_expr_clauses(syntaxTree()) -> [syntaxTree()]
+%%
+%% @doc Returns the list of clause subtrees of a <code>fun_expr</code>
+%% node.
+%%
+%% @see fun_expr/1
+
+fun_expr_clauses(Node) ->
+    case unwrap(Node) of
+	{'fun', _, {clauses, Clauses}} ->
+	    Clauses;
+	Node1 ->
+	    data(Node1)
+    end.
+
+
+%% =====================================================================
+%% @spec fun_expr_arity(syntaxTree()) -> integer()
+%%
+%% @doc Returns the arity of a <code>fun_expr</code> node. The result is
+%% the number of parameter patterns in the first clause of the
+%% fun-expression; subsequent clauses are ignored.
+%%
+%% <p>An exception is thrown if <code>fun_expr_clauses(Node)</code>
+%% returns an empty list, or if the first element of that list is not a
+%% syntax tree <code>C</code> of type <code>clause</code> such that
+%% <code>clause_patterns(C)</code> is a nonempty list.</p>
+%%
+%% @see fun_expr/1
+%% @see fun_expr_clauses/1
+%% @see clause/3
+%% @see clause_patterns/1
+
+fun_expr_arity(Node) ->
+    length(clause_patterns(hd(fun_expr_clauses(Node)))).
+
+
+%% =====================================================================
+%% @spec parentheses(Body::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates an abstract parenthesised expression. The result
+%% represents "<code>(<em>Body</em>)</code>", independently of the
+%% context.
+%%
+%% @see parentheses_body/1
+
+%% type(Node) = parentheses
+%% data(Node) = syntaxTree()
+
+parentheses(Expr) ->
+    tree(parentheses, Expr).
+
+revert_parentheses(Node) ->
+    parentheses_body(Node).
+
+
+%% =====================================================================
+%% @spec parentheses_body(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the body subtree of a <code>parentheses</code> node.
+%%
+%% @see parentheses/1
+
+parentheses_body(Node) ->
+    data(Node).
+
+
+%% =====================================================================
+%% @spec macro(Name) -> syntaxTree()
+%% @equiv macro(Name, none)
+
+macro(Name) ->
+    macro(Name, none).
+
+
+%% =====================================================================
+%% @spec macro(Name::syntaxTree(), Arguments) -> syntaxTree()
+%%	    Arguments = none | [syntaxTree()]
+%%
+%% @doc Creates an abstract macro application. If <code>Arguments</code>
+%% is <code>none</code>, the result represents
+%% "<code>?<em>Name</em></code>", otherwise, if <code>Arguments</code>
+%% is <code>[A1, ..., An]</code>, the result represents
+%% "<code>?<em>Name</em>(<em>A1</em>, ..., <em>An</em>)</code>".
+%%
+%% <p>Notes: if <code>Arguments</code> is the empty list, the result
+%% will thus represent "<code>?<em>Name</em>()</code>", including a pair
+%% of matching parentheses.</p>
+%%
+%% <p>The only syntactical limitation imposed by the preprocessor on the
+%% arguments to a macro application (viewed as sequences of tokens) is
+%% that they must be balanced with respect to parentheses, brackets,
+%% <code>begin ... end</code>, <code>case ... end</code>, etc. The
+%% <code>text</code> node type can be used to represent arguments which
+%% are not regular Erlang constructs.</p>
+%%
+%% @see macro_name/1
+%% @see macro_arguments/1
+%% @see macro/1
+%% @see text/1
+
+-record(macro, {name, arguments}).
+
+%% type(Node) = macro
+%% data(Node) = #macro{name :: Name, arguments :: Arguments}
+%%
+%%	Name = syntaxTree()
+%%	Arguments = none | [syntaxTree()]
+
+macro(Name, Arguments) ->
+    tree(macro, #macro{name = Name, arguments = Arguments}).
+
+
+%% =====================================================================
+%% @spec macro_name(syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns the name subtree of a <code>macro</code> node.
+%%
+%% @see macro/2
+
+macro_name(Node) ->
+    (data(Node))#macro.name.
+
+
+%% =====================================================================
+%% @spec macro_arguments(Node::syntaxTree()) -> none | [syntaxTree()]
+%%
+%% @doc Returns the list of argument subtrees of a <code>macro</code>
+%% node, if any. If <code>Node</code> represents
+%% "<code>?<em>Name</em></code>", <code>none</code> is returned.
+%% Otherwise, if <code>Node</code> represents
+%% "<code>?<em>Name</em>(<em>A1</em>, ..., <em>An</em>)</code>",
+%% <code>[A1, ..., An]</code> is returned.
+%%
+%% @see macro/2
+
+macro_arguments(Node) ->
+    (data(Node))#macro.arguments.
+
+
+%% =====================================================================
+%% @spec abstract(Term::term()) -> syntaxTree()
+%%
+%% @doc Returns the syntax tree corresponding to an Erlang term.
+%% <code>Term</code> must be a literal term, i.e., one that can be
+%% represented as a source code literal. Thus, it may not contain a
+%% process identifier, port, reference, binary or function value as a
+%% subterm. The function recognises printable strings, in order to get a
+%% compact and readable representation. Evaluation fails with reason
+%% <code>badarg</code> if <code>Term</code> is not a literal term.
+%%
+%% @see concrete/1
+%% @see is_literal/1
+
+abstract([H | T] = L) when is_integer(H) ->
+    case is_printable(L) of
+	true ->
+	    string(L);
+	false ->
+	    abstract_tail(H, T)
+    end;
+abstract([H | T]) ->
+    abstract_tail(H, T);
+abstract(T) when is_atom(T) ->
+    atom(T);
+abstract(T) when is_integer(T) ->
+    integer(T);
+abstract(T) when is_float(T) ->
+    make_float(T);    % (not `float', which would call the BIF)
+abstract([]) ->
+    nil();
+abstract(T) when is_tuple(T) ->
+    tuple(abstract_list(tuple_to_list(T)));
+abstract(T) when is_binary(T) ->
+    binary([binary_field(integer(B)) || B <- binary_to_list(T)]);
+abstract(T) ->
+    erlang:error({badarg, T}).
+
+abstract_list([T | Ts]) ->
+    [abstract(T) | abstract_list(Ts)];
+abstract_list([]) ->
+    [].
+
+%% This is entered when we might have a sequence of conses that might or
+%% might not be a proper list, but which should not be considered as a
+%% potential string, to avoid unnecessary checking. This also avoids
+%% that a list like `[4711, 42, 10]' could be abstracted to represent
+%% `[4711 | "*\n"]'.
+
+abstract_tail(H1, [H2 | T]) ->
+    %% Recall that `cons' does "intelligent" composition
+    cons(abstract(H1), abstract_tail(H2, T));
+abstract_tail(H, T) ->
+    cons(abstract(H), abstract(T)).
+
+
+%% =====================================================================
+%% @spec concrete(Node::syntaxTree()) -> term()
+%%
+%% @doc Returns the Erlang term represented by a syntax tree. Evaluation
+%% fails with reason <code>badarg</code> if <code>Node</code> does not
+%% represent a literal term.
+%%
+%% <p>Note: Currently, the set of syntax trees which have a concrete
+%% representation is larger than the set of trees which can be built
+%% using the function <code>abstract/1</code>. An abstract character
+%% will be concretised as an integer, while <code>abstract/1</code> does
+%% not at present yield an abstract character for any input. (Use the
+%% <code>char/1</code> function to explicitly create an abstract
+%% character.)</p>
+%%
+%% @see abstract/1
+%% @see is_literal/1
+%% @see char/1
+
+concrete(Node) ->
+    case type(Node) of
+	atom ->
+	    atom_value(Node);
+	integer ->
+	    integer_value(Node);
+	float ->
+	    float_value(Node);
+	char ->
+	    char_value(Node);
+	string ->
+	    string_value(Node);
+	nil ->
+	    [];
+	list ->
+	    [concrete(list_head(Node))
+	     | concrete(list_tail(Node))];
+	tuple ->
+	    list_to_tuple(concrete_list(tuple_elements(Node)));
+	binary ->
+	    Fs = [revert_binary_field(
+		    binary_field(binary_field_body(F),
+				 case binary_field_size(F) of
+				     none -> none;
+				     S ->
+					 revert(S)
+				 end,
+				 binary_field_types(F)))
+		  || F <- binary_fields(Node)],
+	    {value, B, _} =
+		eval_bits:expr_grp(Fs, [],
+				   fun(F, _) ->
+					   {value, concrete(F), []}
+				   end, [], true),
+	    B;
+    	_ ->
+	    erlang:error({badarg, Node})
+    end.
+
+concrete_list([E | Es]) ->
+    [concrete(E) | concrete_list(Es)];
+concrete_list([]) ->
+    [].
+
+
+%% =====================================================================
+%% @spec is_literal(Node::syntaxTree()) -> bool()
+%%
+%% @doc Returns <code>true</code> if <code>Node</code> represents a
+%% literal term, otherwise <code>false</code>. This function returns
+%% <code>true</code> if and only if the value of
+%% <code>concrete(Node)</code> is defined.
+%%
+%% @see abstract/1
+%% @see concrete/1
+
+is_literal(T) ->
+    case type(T) of
+	atom ->
+	    true;
+	integer ->
+	    true;
+	float ->
+	    true;
+	char->
+	    true;
+	string ->
+	    true;
+	nil ->
+	    true;
+	list ->
+	    is_literal(list_head(T)) andalso is_literal(list_tail(T));
+	tuple ->
+	    lists:all(fun is_literal/1, tuple_elements(T));
+	_ ->
+	    false
+    end.
+
+
+%% =====================================================================
+%% @spec revert(Tree::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Returns an <code>erl_parse</code>-compatible representation of a
+%% syntax tree, if possible. If <code>Tree</code> represents a
+%% well-formed Erlang program or expression, the conversion should work
+%% without problems. Typically, <code>is_tree/1</code> yields
+%% <code>true</code> if conversion failed (i.e., the result is still an
+%% abstract syntax tree), and <code>false</code> otherwise.
+%%
+%% <p>The <code>is_tree/1</code> test is not completely foolproof. For a
+%% few special node types (e.g. <code>arity_qualifier</code>), if such a
+%% node occurs in a context where it is not expected, it will be left
+%% unchanged as a non-reverted subtree of the result. This can only
+%% happen if <code>Tree</code> does not actually represent legal Erlang
+%% code.</p>
+%%
+%% @see revert_forms/1
+%% @see //stdlib/erl_parse
+
+revert(Node) ->
+    case is_tree(Node) of
+	false ->
+	    %% Just remove any wrapper. `erl_parse' nodes never contain
+	    %% abstract syntax tree nodes as subtrees.
+	    unwrap(Node);
+	true ->
+	    case is_leaf(Node) of
+		true ->
+		    revert_root(Node);
+		false ->
+		    %% First revert the subtrees, where possible.
+		    %% (Sometimes, subtrees cannot be reverted out of
+		    %% context, and the real work will be done when the
+		    %% parent node is reverted.)
+		    Gs = [[revert(X) || X <- L] || L <- subtrees(Node)],
+
+		    %% Then reconstruct the node from the reverted
+		    %% parts, and revert the node itself.
+		    Node1 = update_tree(Node, Gs),
+		    revert_root(Node1)
+	    end
+    end.
+
+%% Note: The concept of "compatible root node" is not strictly defined.
+%% At a minimum, if `make_tree' is used to compose a node `T' from
+%% subtrees that are all completely backwards compatible, then the
+%% result of `revert_root(T)' should also be completely backwards
+%% compatible.
+
+revert_root(Node) ->
+    case type(Node) of
+	application ->
+	    revert_application(Node);
+	atom ->
+	    revert_atom(Node);
+	attribute ->
+	    revert_attribute(Node);
+	binary ->
+	    revert_binary(Node);
+        binary_comp ->
+	    revert_binary_comp(Node);
+	binary_field ->
+	    revert_binary_field(Node);
+        binary_generator ->
+	    revert_binary_generator(Node);
+	block_expr ->
+	    revert_block_expr(Node);
+	case_expr ->
+	    revert_case_expr(Node);
+	catch_expr ->
+	    revert_catch_expr(Node);
+	char ->
+	    revert_char(Node);
+	clause ->
+	    revert_clause(Node);
+	cond_expr ->
+	    revert_cond_expr(Node);
+	eof_marker ->
+	    revert_eof_marker(Node);
+	error_marker ->
+	    revert_error_marker(Node);
+	float ->
+	    revert_float(Node);
+	fun_expr ->
+	    revert_fun_expr(Node);
+	function ->
+	    revert_function(Node);
+	generator ->
+	    revert_generator(Node);
+	if_expr ->
+	    revert_if_expr(Node);
+	implicit_fun ->
+	    revert_implicit_fun(Node);
+	infix_expr ->
+	    revert_infix_expr(Node);
+	integer ->
+	    revert_integer(Node);
+	list ->
+	    revert_list(Node);
+	list_comp ->
+	    revert_list_comp(Node);
+	match_expr ->
+	    revert_match_expr(Node);
+	module_qualifier ->
+	    revert_module_qualifier(Node);
+	nil ->
+	    revert_nil(Node);
+	parentheses ->
+	    revert_parentheses(Node);
+	prefix_expr ->
+	    revert_prefix_expr(Node);
+	qualified_name ->
+	    revert_qualified_name(Node);
+	query_expr ->
+	    revert_query_expr(Node);
+	receive_expr ->
+	    revert_receive_expr(Node);
+	record_access ->
+	    revert_record_access(Node);
+	record_expr ->
+	    revert_record_expr(Node);
+	record_index_expr ->
+	    revert_record_index_expr(Node);
+	rule ->
+	    revert_rule(Node);
+	string ->
+	    revert_string(Node);
+	try_expr ->
+	    revert_try_expr(Node);
+	tuple ->
+	    revert_tuple(Node);
+	underscore ->
+	    revert_underscore(Node);
+	variable ->
+	    revert_variable(Node);
+	warning_marker ->
+	    revert_warning_marker(Node);
+	_ ->
+	    %% Non-revertible new-form node
+	    Node
+    end.
+
+
+%% =====================================================================
+%% @spec revert_forms(Forms) -> [erl_parse()]
+%%
+%%	    Forms = syntaxTree() | [syntaxTree()]
+%%
+%% @doc Reverts a sequence of Erlang source code forms. The sequence can
+%% be given either as a <code>form_list</code> syntax tree (possibly
+%% nested), or as a list of "program form" syntax trees. If successful,
+%% the corresponding flat list of <code>erl_parse</code>-compatible
+%% syntax trees is returned (cf. <code>revert/1</code>). If some program
+%% form could not be reverted, <code>{error, Form}</code> is thrown.
+%% Standalone comments in the form sequence are discarded.
+%%
+%% @see revert/1
+%% @see form_list/1
+%% @see is_form/1
+
+revert_forms(L) when is_list(L) ->
+    revert_forms(form_list(L));
+revert_forms(T) ->
+    case type(T) of
+	form_list ->
+	    T1 = flatten_form_list(T),
+	    case catch {ok, revert_forms_1(form_list_elements(T1))} of
+		{ok, Fs} ->
+		    Fs;
+		{error, _} = Error ->
+		    erlang:error(Error);
+		{'EXIT', R} ->
+		    exit(R);
+		R ->
+		    throw(R)
+	    end;
+	_ ->
+	    erlang:error({badarg, T})
+    end.
+
+revert_forms_1([T | Ts]) ->
+    case type(T) of
+	comment ->
+	    revert_forms_1(Ts);
+	_ ->
+	    T1 = revert(T),
+	    case is_tree(T1) of
+		true ->
+		    throw({error, T1});
+		false ->
+		    [T1 | revert_forms_1(Ts)]
+	    end
+    end;
+revert_forms_1([]) ->
+    [].
+
+
+%% =====================================================================
+%% @spec subtrees(Node::syntaxTree()) -> [[syntaxTree()]]
+%%
+%% @doc Returns the grouped list of all subtrees of a syntax tree. If
+%% <code>Node</code> is a leaf node (cf. <code>is_leaf/1</code>), this
+%% is the empty list, otherwise the result is always a nonempty list,
+%% containing the lists of subtrees of <code>Node</code>, in
+%% left-to-right order as they occur in the printed program text, and
+%% grouped by category. Often, each group contains only a single
+%% subtree.
+%%
+%% <p>Depending on the type of <code>Node</code>, the size of some
+%% groups may be variable (e.g., the group consisting of all the
+%% elements of a tuple), while others always contain the same number of
+%% elements - usually exactly one (e.g., the group containing the
+%% argument expression of a case-expression). Note, however, that the
+%% exact structure of the returned list (for a given node type) should
+%% in general not be depended upon, since it might be subject to change
+%% without notice.</p>
+%%
+%% <p>The function <code>subtrees/1</code> and the constructor functions
+%% <code>make_tree/2</code> and <code>update_tree/2</code> can be a
+%% great help if one wants to traverse a syntax tree, visiting all its
+%% subtrees, but treat nodes of the tree in a uniform way in most or all
+%% cases. Using these functions makes this simple, and also assures that
+%% your code is not overly sensitive to extensions of the syntax tree
+%% data type, because any node types not explicitly handled by your code
+%% can be left to a default case.</p>
+%%
+%% <p>For example:
+%% <pre>
+%%   postorder(F, Tree) ->
+%%       F(case subtrees(Tree) of
+%%           [] -> Tree;
+%%           List -> update_tree(Tree,
+%%                               [[postorder(F, Subtree)
+%%                                 || Subtree &lt;- Group]
+%%                                || Group &lt;- List])
+%%         end).
+%% </pre>
+%% maps the function <code>F</code> on <code>Tree</code> and all its
+%% subtrees, doing a post-order traversal of the syntax tree. (Note the
+%% use of <code>update_tree/2</code> to preserve node attributes.) For a
+%% simple function like:
+%% <pre>
+%%   f(Node) ->
+%%       case type(Node) of
+%%           atom -> atom("a_" ++ atom_name(Node));
+%%           _ -> Node
+%%       end.
+%% </pre>
+%% the call <code>postorder(fun f/1, Tree)</code> will yield a new
+%% representation of <code>Tree</code> in which all atom names have been
+%% extended with the prefix "a_", but nothing else (including comments,
+%% annotations and line numbers) has been changed.</p>
+%%
+%% @see make_tree/2
+%% @see type/1
+%% @see is_leaf/1
+%% @see copy_attrs/2
+
+subtrees(T) ->
+    case is_leaf(T) of
+	true ->
+	    [];
+	false ->
+	    case type(T) of
+		application ->
+		    [[application_operator(T)],
+		     application_arguments(T)];
+		arity_qualifier ->
+		    [[arity_qualifier_body(T)],
+		     [arity_qualifier_argument(T)]];
+		attribute ->
+		    case attribute_arguments(T) of
+			none ->
+			    [[attribute_name(T)]];
+			As ->
+			    [[attribute_name(T)], As]
+		    end;
+		binary ->
+		    [binary_fields(T)];
+		binary_comp ->
+		    [[binary_comp_template(T)], binary_comp_body(T)];
+                binary_field ->
+		    case binary_field_types(T) of
+			[] ->
+			    [[binary_field_body(T)]];
+			Ts ->
+			    [[binary_field_body(T)],
+			     Ts]
+		    end;
+	        binary_generator ->
+		    [[binary_generator_pattern(T)], 
+                     [binary_generator_body(T)]];
+		block_expr ->
+		    [block_expr_body(T)];
+		case_expr ->
+		    [[case_expr_argument(T)],
+		     case_expr_clauses(T)];
+		catch_expr ->
+		    [[catch_expr_body(T)]];
+		class_qualifier ->
+		    [[class_qualifier_argument(T)],
+		     [class_qualifier_body(T)]];
+		clause ->
+		    case clause_guard(T) of
+			none ->
+			    [clause_patterns(T), clause_body(T)];
+			G ->
+			    [clause_patterns(T), [G],
+			     clause_body(T)]
+		    end;
+		cond_expr ->
+		    [cond_expr_clauses(T)];
+		conjunction ->
+		    [conjunction_body(T)];
+		disjunction ->
+		    [disjunction_body(T)];
+		form_list ->
+		    [form_list_elements(T)];
+		fun_expr ->
+		    [fun_expr_clauses(T)];
+		function ->
+		    [[function_name(T)], function_clauses(T)];
+		generator ->
+		    [[generator_pattern(T)], [generator_body(T)]];
+		if_expr ->
+		    [if_expr_clauses(T)];
+		implicit_fun ->
+		    [[implicit_fun_name(T)]];
+		infix_expr ->
+		    [[infix_expr_left(T)],
+		     [infix_expr_operator(T)],
+		     [infix_expr_right(T)]];
+		list ->
+		    case list_suffix(T) of
+			none ->
+			    [list_prefix(T)];
+			S ->
+			    [list_prefix(T), [S]]
+		    end;
+		list_comp ->
+		    [[list_comp_template(T)], list_comp_body(T)];
+		macro ->
+		    case macro_arguments(T) of
+			none ->
+			    [[macro_name(T)]];
+			As ->
+			    [[macro_name(T)], As]
+		    end;
+		match_expr ->
+		    [[match_expr_pattern(T)],
+		     [match_expr_body(T)]];
+		module_qualifier ->
+		    [[module_qualifier_argument(T)],
+		     [module_qualifier_body(T)]];
+		parentheses ->
+		    [[parentheses_body(T)]];
+		prefix_expr ->
+		    [[prefix_expr_operator(T)],
+		     [prefix_expr_argument(T)]];
+		qualified_name ->
+		    [qualified_name_segments(T)];
+		query_expr ->
+		    [[query_expr_body(T)]];
+		receive_expr ->
+		    case receive_expr_timeout(T) of
+			none ->
+			    [receive_expr_clauses(T)];
+			E ->
+			    [receive_expr_clauses(T),
+			     [E],
+			     receive_expr_action(T)]
+		    end;
+		record_access ->
+		    case record_access_type(T) of
+			none ->
+			    [[record_access_argument(T)],
+			     [record_access_field(T)]];
+			R ->
+			    [[record_access_argument(T)],
+			     [R],
+			     [record_access_field(T)]]
+		    end;
+		record_expr ->
+		    case record_expr_argument(T) of
+			none ->
+			    [[record_expr_type(T)],
+			     record_expr_fields(T)];
+			V ->
+			    [[V],
+			     [record_expr_type(T)],
+			     record_expr_fields(T)]
+		    end;
+		record_field ->
+		    case record_field_value(T) of
+			none ->
+			    [[record_field_name(T)]];
+			V ->
+			    [[record_field_name(T)], [V]]
+		    end;
+		record_index_expr ->
+		    [[record_index_expr_type(T)],
+		     [record_index_expr_field(T)]];
+		rule ->
+		    [[rule_name(T)], rule_clauses(T)];
+		size_qualifier ->
+		    [[size_qualifier_body(T)],
+		     [size_qualifier_argument(T)]];
+		try_expr ->
+		    [try_expr_body(T),
+		     try_expr_clauses(T),
+		     try_expr_handlers(T),
+		     try_expr_after(T)];
+		tuple ->
+		    [tuple_elements(T)]
+	    end
+    end.
+
+
+%% =====================================================================
+%% @spec update_tree(Node::syntaxTree(), Groups::[[syntaxTree()]]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates a syntax tree with the same type and attributes as the
+%% given tree. This is equivalent to <code>copy_attrs(Node,
+%% make_tree(type(Node), Groups))</code>.
+%%
+%% @see make_tree/2
+%% @see copy_attrs/2
+%% @see type/1
+
+update_tree(Node, Groups) ->
+    copy_attrs(Node, make_tree(type(Node), Groups)).
+
+
+%% =====================================================================
+%% @spec make_tree(Type::atom(), Groups::[[syntaxTree()]]) ->
+%%           syntaxTree()
+%%
+%% @doc Creates a syntax tree with the given type and subtrees.
+%% <code>Type</code> must be a node type name (cf. <code>type/1</code>)
+%% that does not denote a leaf node type (cf. <code>is_leaf/1</code>).
+%% <code>Groups</code> must be a <em>nonempty</em> list of groups of
+%% syntax trees, representing the subtrees of a node of the given type,
+%% in left-to-right order as they would occur in the printed program
+%% text, grouped by category as done by <code>subtrees/1</code>.
+%%
+%% <p>The result of <code>copy_attrs(Node, make_tree(type(Node),
+%% subtrees(Node)))</code> (cf. <code>update_tree/2</code>) represents
+%% the same source code text as the original <code>Node</code>, assuming
+%% that <code>subtrees(Node)</code> yields a nonempty list. However, it
+%% does not necessarily have the same data representation as
+%% <code>Node</code>.</p>
+%%
+%% @see update_tree/2
+%% @see subtrees/1
+%% @see type/1
+%% @see is_leaf/1
+%% @see copy_attrs/2
+
+make_tree(application, [[F], A]) -> application(F, A);
+make_tree(arity_qualifier, [[N], [A]]) -> arity_qualifier(N, A);
+make_tree(attribute, [[N]]) -> attribute(N);
+make_tree(attribute, [[N], A]) -> attribute(N, A);
+make_tree(binary, [Fs]) -> binary(Fs);
+make_tree(binary_comp, [[T], B]) -> binary_comp(T, B);
+make_tree(binary_field, [[B]]) -> binary_field(B);
+make_tree(binary_field, [[B], Ts]) -> binary_field(B, Ts);
+make_tree(binary_generator, [[P], [E]]) -> binary_generator(P, E);
+make_tree(block_expr, [B]) -> block_expr(B);
+make_tree(case_expr, [[A], C]) -> case_expr(A, C);
+make_tree(catch_expr, [[B]]) -> catch_expr(B);
+make_tree(class_qualifier, [[A], [B]]) -> class_qualifier(A, B);
+make_tree(clause, [P, B]) -> clause(P, none, B);
+make_tree(clause, [P, [G], B]) -> clause(P, G, B);
+make_tree(cond_expr, [C]) -> cond_expr(C);
+make_tree(conjunction, [E]) -> conjunction(E);
+make_tree(disjunction, [E]) -> disjunction(E);
+make_tree(form_list, [E]) -> form_list(E);
+make_tree(fun_expr, [C]) -> fun_expr(C);
+make_tree(function, [[N], C]) -> function(N, C);
+make_tree(generator, [[P], [E]]) -> generator(P, E);
+make_tree(if_expr, [C]) -> if_expr(C);
+make_tree(implicit_fun, [[N]]) -> implicit_fun(N);
+make_tree(infix_expr, [[L], [F], [R]]) -> infix_expr(L, F, R);
+make_tree(list, [P]) -> list(P);
+make_tree(list, [P, [S]]) -> list(P, S);
+make_tree(list_comp, [[T], B]) -> list_comp(T, B);
+make_tree(macro, [[N]]) -> macro(N);
+make_tree(macro, [[N], A]) -> macro(N, A);
+make_tree(match_expr, [[P], [E]]) -> match_expr(P, E);
+make_tree(module_qualifier, [[M], [N]]) -> module_qualifier(M, N);
+make_tree(parentheses, [[E]]) -> parentheses(E);
+make_tree(prefix_expr, [[F], [A]]) -> prefix_expr(F, A);
+make_tree(qualified_name, [S]) -> qualified_name(S);
+make_tree(query_expr, [[B]]) -> query_expr(B);
+make_tree(receive_expr, [C]) -> receive_expr(C);
+make_tree(receive_expr, [C, [E], A]) -> receive_expr(C, E, A);
+make_tree(record_access, [[E], [F]]) ->
+    record_access(E, F);
+make_tree(record_access, [[E], [T], [F]]) ->
+    record_access(E, T, F);
+make_tree(record_expr, [[T], F]) -> record_expr(T, F);
+make_tree(record_expr, [[E], [T], F]) -> record_expr(E, T, F);
+make_tree(record_field, [[N]]) -> record_field(N);
+make_tree(record_field, [[N], [E]]) -> record_field(N, E);
+make_tree(record_index_expr, [[T], [F]]) ->
+    record_index_expr(T, F);
+make_tree(rule, [[N], C]) -> rule(N, C);
+make_tree(size_qualifier, [[N], [A]]) -> size_qualifier(N, A);
+make_tree(try_expr, [B, C, H, A]) -> try_expr(B, C, H, A);
+make_tree(tuple, [E]) -> tuple(E).
+
+
+%% =====================================================================
+%% @spec meta(Tree::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Creates a meta-representation of a syntax tree. The result
+%% represents an Erlang expression "<code><em>MetaTree</em></code>"
+%% which, if evaluated, will yield a new syntax tree representing the
+%% same source code text as <code>Tree</code> (although the actual data
+%% representation may be different). The expression represented by
+%% <code>MetaTree</code> is <em>implementation independent</em> with
+%% regard to the data structures used by the abstract syntax tree
+%% implementation. Comments attached to nodes of <code>Tree</code> will
+%% be preserved, but other attributes are lost.
+%%
+%% <p>Any node in <code>Tree</code> whose node type is
+%% <code>variable</code> (cf. <code>type/1</code>), and whose list of
+%% annotations (cf. <code>get_ann/1</code>) contains the atom
+%% <code>meta_var</code>, will remain unchanged in the resulting tree,
+%% except that exactly one occurrence of <code>meta_var</code> is
+%% removed from its annotation list.</p>
+%%
+%% <p>The main use of the function <code>meta/1</code> is to transform a
+%% data structure <code>Tree</code>, which represents a piece of program
+%% code, into a form that is <em>representation independent when
+%% printed</em>. E.g., suppose <code>Tree</code> represents a variable
+%% named "V". Then (assuming a function <code>print/1</code> for
+%% printing syntax trees), evaluating <code>print(abstract(Tree))</code>
+%% - simply using <code>abstract/1</code> to map the actual data
+%% structure onto a syntax tree representation - would output a string
+%% that might look something like "<code>{tree, variable, ..., "V",
+%% ...}</code>", which is obviously dependent on the implementation of
+%% the abstract syntax trees. This could e.g. be useful for caching a
+%% syntax tree in a file. However, in some situations like in a program
+%% generator generator (with two "generator"), it may be unacceptable.
+%% Using <code>print(meta(Tree))</code> instead would output a
+%% <em>representation independent</em> syntax tree generating
+%% expression; in the above case, something like
+%% "<code>erl_syntax:variable("V")</code>".</p>
+%%
+%% @see abstract/1
+%% @see type/1
+%% @see get_ann/1
+
+meta(T) ->
+    %% First of all we check for metavariables:
+    case type(T) of
+	variable ->
+	    case lists:member(meta_var, get_ann(T)) of
+		false ->
+		    meta_precomment(T);
+		true ->
+		    %% A meta-variable: remove the first found
+		    %% `meta_var' annotation, but otherwise leave
+		    %% the node unchanged.
+		    set_ann(T, lists:delete(meta_var, get_ann(T)))
+	    end;
+	_ ->
+	    case has_comments(T) of
+		true ->
+		    meta_precomment(T);
+		false ->
+		    meta_1(T)
+	    end
+    end.
+
+meta_precomment(T) ->
+    case get_precomments(T) of
+	[] ->
+	    meta_postcomment(T);
+	Cs ->
+	    meta_call(set_precomments,
+		      [meta_postcomment(T), list(meta_list(Cs))])
+    end.
+
+meta_postcomment(T) ->
+    case get_postcomments(T) of
+	[] ->
+	    meta_0(T);
+	Cs ->
+	    meta_call(set_postcomments,
+		      [meta_0(T), list(meta_list(Cs))])
+    end.
+
+meta_0(T) ->
+    meta_1(remove_comments(T)).
+
+meta_1(T) ->
+    %% First handle leaf nodes and other common cases, in order to
+    %% generate compact code.
+    case type(T) of
+	atom ->
+	    meta_call(atom, [T]);
+	char ->
+	    meta_call(char, [T]);
+	comment ->
+	    meta_call(comment, [list([string(S)
+				      || S <- comment_text(T)])]);
+	eof_marker ->
+	    meta_call(eof_marker, []);
+	error_marker ->
+	    meta_call(error_marker,
+		      [abstract(error_marker_info(T))]);
+	float ->
+	    meta_call(float, [T]);
+	integer ->
+	    meta_call(integer, [T]);
+	nil ->
+	    meta_call(nil, []);
+	operator ->
+	    meta_call(operator, [atom(operator_name(T))]);
+	string ->
+	    meta_call(string, [T]);
+	text ->
+	    meta_call(text, [string(text_string(T))]);
+	underscore ->
+	    meta_call(underscore, []);
+	variable ->
+	    meta_call(variable, [string(atom_to_list(variable_name(T)))]);
+	warning_marker ->
+	    meta_call(warning_marker,
+		      [abstract(warning_marker_info(T))]);
+	list ->
+	    case list_suffix(T) of
+		none ->
+		    meta_call(list,
+			      [list(meta_list(list_prefix(T)))]);
+		S ->
+		    meta_call(list,
+			      [list(meta_list(list_prefix(T))),
+			       meta(S)])
+	    end;
+	tuple ->
+	    meta_call(tuple,
+		      [list(meta_list(tuple_elements(T)))]);
+	Type ->
+	    %% All remaining cases are handled using `subtrees'
+	    %% and `make_tree' to decompose and reassemble the
+	    %% nodes. More cases could of course be handled
+	    %% directly to get a more compact output, but I can't
+	    %% be bothered right now.
+	    meta_call(make_tree,
+		      [abstract(Type),
+		       meta_subtrees(subtrees(T))])
+    end.
+
+meta_list([T | Ts]) ->
+    [meta(T) | meta_list(Ts)];
+meta_list([]) ->
+    [].
+
+meta_subtrees(Gs) ->
+    list([list([meta(T)
+		|| T <- G])
+	  || G <- Gs]).
+
+meta_call(F, As) ->
+    application(atom(?MODULE), atom(F), As).
+
+
+%% =====================================================================
+%% Functions for abstraction of the syntax tree representation; may be
+%% used externally, but not intended for the normal user.
+%% =====================================================================
+
+
+%% =====================================================================
+%% @spec tree(Type) -> syntaxTree()
+%% @equiv tree(Type, [])
+
+tree(Type) ->
+    tree(Type, []).
+
+%% =====================================================================
+%% @spec tree(Type::atom(), Data::term()) -> syntaxTree()
+%%
+%% @doc <em>For special purposes only</em>. Creates an abstract syntax
+%% tree node with type tag <code>Type</code> and associated data
+%% <code>Data</code>.
+%%
+%% <p>This function and the related <code>is_tree/1</code> and
+%% <code>data/1</code> provide a uniform way to extend the set of
+%% <code>erl_parse</code> node types. The associated data is any term,
+%% whose format may depend on the type tag.</p>
+%%
+%% <h4>Notes:</h4>
+%% <ul>
+%%  <li>Any nodes created outside of this module must have type tags
+%%      distinct from those currently defined by this module; see
+%%      <code>type/1</code> for a complete list.</li>
+%%  <li>The type tag of a syntax tree node may also be used
+%%      as a primary tag by the <code>erl_parse</code> representation;
+%%      in that case, the selector functions for that node type
+%%      <em>must</em> handle both the abstract syntax tree and the
+%%      <code>erl_parse</code> form. The function <code>type(T)</code>
+%%      should return the correct type tag regardless of the
+%%      representation of <code>T</code>, so that the user sees no
+%%      difference between <code>erl_syntax</code> and
+%%      <code>erl_parse</code> nodes.</li>
+%% </ul>
+%% @see is_tree/1
+%% @see data/1
+%% @see type/1
+
+tree(Type, Data) ->
+    #tree{type = Type, data = Data}.
+
+
+%% =====================================================================
+%% @spec is_tree(Tree::syntaxTree()) -> bool()
+%%
+%% @doc <em>For special purposes only</em>. Returns <code>true</code> if
+%% <code>Tree</code> is an abstract syntax tree and <code>false</code>
+%% otherwise.
+%%
+%% <p><em>Note</em>: this function yields <code>false</code> for all
+%% "old-style" <code>erl_parse</code>-compatible "parse trees".</p>
+%%
+%% @see tree/2
+
+is_tree(#tree{}) ->
+    true;
+is_tree(_) ->
+    false.
+
+
+%% =====================================================================
+%% @spec data(Tree::syntaxTree()) -> term()
+%%
+%% @doc <em>For special purposes only</em>. Returns the associated data
+%% of a syntax tree node. Evaluation fails with reason
+%% <code>badarg</code> if <code>is_tree(Node)</code> does not yield
+%% <code>true</code>.
+%%
+%% @see tree/2
+
+data(#tree{data = D}) -> D;
+data(T) -> erlang:error({badarg, T}).
+
+
+%% =====================================================================
+%% Primitives for backwards compatibility; for internal use only
+%% =====================================================================
+
+
+%% =====================================================================
+%% @spec wrap(Node::erl_parse()) -> syntaxTree()
+%%
+%% @type erl_parse() = erl_parse:parse_tree(). The "parse tree"
+%% representation built by the Erlang standard library parser
+%% <code>erl_parse</code>. This is a subset of the
+%% <a href="#type-syntaxTree"><code>syntaxTree</code></a> type.
+%%
+%% @doc Creates a wrapper structure around an <code>erl_parse</code>
+%% "parse tree".
+%%
+%% <p>This function and the related <code>unwrap/1</code> and
+%% <code>is_wrapper/1</code> provide a uniform way to attach arbitrary
+%% information to an <code>erl_parse</code> tree. Some information about
+%% the encapsuled tree may be cached in the wrapper, such as the node
+%% type. All functions on syntax trees must behave so that the user sees
+%% no difference between wrapped and non-wrapped <code>erl_parse</code>
+%% trees. <em>Attaching a wrapper onto another wrapper structure is an
+%% error</em>.</p>
+
+wrap(Node) ->
+    %% We assume that Node is an old-school `erl_parse' tree.
+    #wrapper{type = type(Node), attr = #attr{pos = get_pos(Node)},
+	     tree = Node}.
+
+
+%% =====================================================================
+%% @spec unwrap(Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Removes any wrapper structure, if present. If <code>Node</code>
+%% is a wrapper structure, this function returns the wrapped
+%% <code>erl_parse</code> tree; otherwise it returns <code>Node</code>
+%% itself.
+
+unwrap(#wrapper{tree = Node}) -> Node;
+unwrap(Node) -> Node.	 % This could also be a new-form node.
+
+
+%% =====================================================================
+%% @spec is_wrapper(Term::term()) -> bool()
+%%
+%% @doc Returns <code>true</code> if the argument is a wrapper
+%% structure, otherwise <code>false</code>.
+
+-ifndef(NO_UNUSED).
+is_wrapper(#wrapper{}) ->
+    true;
+is_wrapper(_) ->
+    false.
+-endif.
+
+
+%% =====================================================================
+%% General utility functions for internal use
+%% =====================================================================
+
+is_printable(S) ->
+    io_lib:printable_list(S).
+
+%% Support functions for transforming lists of function names
+%% specified as `arity_qualifier' nodes.
+
+unfold_function_names(Ns, Pos) ->
+    F = fun ({Atom, Arity}) ->
+		N = arity_qualifier(atom(Atom), integer(Arity)),
+		set_pos(N, Pos)
+	end,
+    [F(N) || N <- Ns].
+
+fold_function_names(Ns) ->
+    [fold_function_name(N) || N <- Ns].
+
+fold_function_name(N) ->
+    Name = arity_qualifier_body(N),
+    Arity = arity_qualifier_argument(N),
+    true = ((type(Name) =:= atom) and (type(Arity) =:= integer)),
+    {concrete(Name), concrete(Arity)}.
+
+fold_variable_names(Vs) ->
+    [variable_name(V) || V <- Vs].
+
+unfold_variable_names(Vs, Pos) ->
+    [set_pos(variable(V), Pos) || V <- Vs].
+
+%% Support functions for qualified names ("foo.bar.baz",
+%% "erl.lang.lists", etc.). The representation overlaps with the weird
+%% "Mnesia query record access" operators. The '.' operator is left
+%% associative, so folding should nest on the left.
+
+is_qualified_name({record_field, _, L, R}) ->
+    is_qualified_name(L) andalso is_qualified_name(R);
+is_qualified_name({atom, _, _}) -> true;
+is_qualified_name(_) -> false.
+
+unfold_qualified_name(Node) ->
+    lists:reverse(unfold_qualified_name(Node, [])).
+
+unfold_qualified_name({record_field, _, L, R}, Ss) ->
+    unfold_qualified_name(R, unfold_qualified_name(L, Ss));
+unfold_qualified_name(S, Ss) -> [S | Ss].
+
+fold_qualified_name([S | Ss], Pos) ->
+    fold_qualified_name(Ss, Pos, {atom, Pos, atom_value(S)}).
+
+fold_qualified_name([S | Ss], Pos, Ack) ->
+    fold_qualified_name(Ss, Pos, {record_field, Pos, Ack,
+				  {atom, Pos, atom_value(S)}});
+fold_qualified_name([], _Pos, Ack) ->
+    Ack.
+
+%% Support functions for transforming lists of record field definitions.
+%%
+%% There is no unique representation for field definitions in the
+%% standard form. There, they may only occur in the "fields" part of a
+%% record expression or declaration, and are represented as
+%% `{record_field, Pos, Name, Value}', or as `{record_field, Pos, Name}'
+%% if the value part is left out. However, these cannot be distinguished
+%% out of context from the representation of record field access
+%% expressions (see `record_access').
+
+fold_record_fields(Fs) ->
+    [fold_record_field(F) || F <- Fs].
+
+fold_record_field(F) ->
+    Pos = get_pos(F),
+    Name = record_field_name(F),
+    case record_field_value(F) of
+	none ->
+	    {record_field, Pos, Name};
+	Value ->
+	    {record_field, Pos, Name, Value}
+    end.
+
+unfold_record_fields(Fs) ->
+    [unfold_record_field(F) || F <- Fs].
+
+unfold_record_field({typed_record_field, Field, _Type}) ->
+  unfold_record_field_1(Field);
+unfold_record_field(Field) ->
+  unfold_record_field_1(Field).
+
+unfold_record_field_1({record_field, Pos, Name}) ->
+    set_pos(record_field(Name), Pos);
+unfold_record_field_1({record_field, Pos, Name, Value}) ->
+    set_pos(record_field(Name, Value), Pos).
+
+fold_binary_field_types(Ts) ->
+    [fold_binary_field_type(T) || T <- Ts].
+
+fold_binary_field_type(Node) ->
+    case type(Node) of
+	size_qualifier ->
+	    {concrete(size_qualifier_body(Node)),
+	     concrete(size_qualifier_argument(Node))};
+	_ ->
+	    concrete(Node)
+    end.
+
+unfold_binary_field_types(Ts, Pos) ->
+    [unfold_binary_field_type(T, Pos) || T <- Ts].
+
+unfold_binary_field_type({Type, Size}, Pos) ->
+    set_pos(size_qualifier(atom(Type), integer(Size)), Pos);
+unfold_binary_field_type(Type, Pos) ->
+    set_pos(atom(Type), Pos).
+
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/erl_syntax_lib.erl b/lib/syntax_tools/src/erl_syntax_lib.erl
new file mode 100644
index 0000000000..ccbf864c2a
--- /dev/null
+++ b/lib/syntax_tools/src/erl_syntax_lib.erl
@@ -0,0 +1,2168 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1997-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Support library for abstract Erlang syntax trees.
+%%
+%% This module contains utility functions for working with the
+%% abstract data type defined in the module {@link erl_syntax}.
+%%
+%% @type syntaxTree() = erl_syntax:syntaxTree(). An abstract syntax
+%% tree. See the {@link erl_syntax} module for details.
+
+-module(erl_syntax_lib).
+
+-export([analyze_application/1, analyze_attribute/1,
+         analyze_export_attribute/1, analyze_file_attribute/1,
+         analyze_form/1, analyze_forms/1, analyze_function/1,
+         analyze_function_name/1, analyze_implicit_fun/1,
+         analyze_import_attribute/1, analyze_module_attribute/1,
+         analyze_record_attribute/1, analyze_record_expr/1,
+         analyze_record_field/1, analyze_rule/1,
+         analyze_wild_attribute/1, annotate_bindings/1,
+         annotate_bindings/2, fold/3, fold_subtrees/3, foldl_listlist/3,
+         function_name_expansions/1, is_fail_expr/1, limit/2, limit/3,
+         map/2, map_subtrees/2, mapfold/3, mapfold_subtrees/3,
+         mapfoldl_listlist/3, new_variable_name/1, new_variable_name/2,
+         new_variable_names/2, new_variable_names/3, strip_comments/1,
+         to_comment/1, to_comment/2, to_comment/3, variables/1]).
+
+
+%% =====================================================================
+%% @spec map(Function, Tree::syntaxTree()) -> syntaxTree()
+%%
+%%          Function = (syntaxTree()) -> syntaxTree()
+%% 
+%% @doc Applies a function to each node of a syntax tree. The result of
+%% each application replaces the corresponding original node. The order
+%% of traversal is bottom-up.
+%%
+%% @see map_subtrees/2
+
+map(F, Tree) ->
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            F(Tree);
+        Gs ->
+            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree),
+                                         [[map(F, T) || T <- G]
+                                          || G <- Gs]),
+            F(erl_syntax:copy_attrs(Tree, Tree1))
+    end.
+
+
+%% =====================================================================
+%% @spec map_subtrees(Function, syntaxTree()) -> syntaxTree()
+%%
+%%          Function = (Tree) -> Tree1
+%%         
+%% @doc Applies a function to each immediate subtree of a syntax tree.
+%% The result of each application replaces the corresponding original
+%% node.
+%%
+%% @see map/2
+
+map_subtrees(F, Tree) ->
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            Tree;
+        Gs ->
+            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree),
+                                         [[F(T) || T <- G] || G <- Gs]),
+            erl_syntax:copy_attrs(Tree, Tree1)
+    end.
+
+
+%% =====================================================================
+%% @spec fold(Function, Start::term(), Tree::syntaxTree()) -> term()
+%%
+%%          Function = (syntaxTree(), term()) -> term()
+%%
+%% @doc Folds a function over all nodes of a syntax tree. The result is
+%% the value of `Function(X1, Function(X2, ... Function(Xn, Start)
+%% ... ))', where `[X1, X2, ..., Xn]' are the nodes of
+%% `Tree' in a post-order traversal.
+%%
+%% @see fold_subtrees/3
+%% @see foldl_listlist/3
+
+fold(F, S, Tree) ->
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            F(Tree, S);
+        Gs ->
+            F(Tree, fold_1(F, S, Gs))
+    end.
+
+fold_1(F, S, [L | Ls]) ->
+    fold_1(F, fold_2(F, S, L), Ls);
+fold_1(_, S, []) ->
+    S.
+
+fold_2(F, S, [T | Ts]) ->
+    fold_2(F, fold(F, S, T), Ts);
+fold_2(_, S, []) ->
+    S.
+
+
+%% =====================================================================
+%% @spec fold_subtrees(Function, Start::term(), Tree::syntaxTree()) ->
+%%           term()
+%%
+%%          Function = (syntaxTree(), term()) -> term()
+%%
+%% @doc Folds a function over the immediate subtrees of a syntax tree.
+%% This is similar to `fold/3', but only on the immediate
+%% subtrees of `Tree', in left-to-right order; it does not
+%% include the root node of `Tree'.
+%%
+%% @see fold/3
+
+fold_subtrees(F, S, Tree) ->
+    foldl_listlist(F, S, erl_syntax:subtrees(Tree)).
+
+
+%% =====================================================================
+%% @spec foldl_listlist(Function, Start::term(), [[term()]]) -> term()
+%%
+%%          Function = (term(), term()) -> term()
+%%
+%% @doc Like `lists:foldl/3', but over a list of lists.
+%%
+%% @see fold/3
+%% @see //stdlib/lists:foldl/3
+
+foldl_listlist(F, S, [L | Ls]) ->
+    foldl_listlist(F, foldl(F, S, L), Ls);
+foldl_listlist(_, S, []) ->
+    S.
+
+foldl(F, S, [T | Ts]) ->
+    foldl(F, F(T, S), Ts);
+foldl(_, S, []) ->
+    S.
+
+
+%% =====================================================================
+%% @spec mapfold(Function, Start::term(), Tree::syntaxTree()) ->
+%%           {syntaxTree(), term()}
+%%
+%%          Function = (syntaxTree(), term()) -> {syntaxTree(), term()}
+%%
+%% @doc Combines map and fold in a single operation. This is similar to
+%% `map/2', but also propagates an extra value from each
+%% application of the `Function' to the next, while doing a
+%% post-order traversal of the tree like `fold/3'. The value
+%% `Start' is passed to the first function application, and
+%% the final result is the result of the last application.
+%%
+%% @see map/2
+%% @see fold/3
+
+mapfold(F, S, Tree) ->
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            F(Tree, S);
+        Gs ->
+            {Gs1, S1} = mapfold_1(F, S, Gs),
+            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree), Gs1),
+            F(erl_syntax:copy_attrs(Tree, Tree1), S1)
+    end.
+
+mapfold_1(F, S, [L | Ls]) ->
+    {L1, S1} = mapfold_2(F, S, L),
+    {Ls1, S2} = mapfold_1(F, S1, Ls),
+    {[L1 | Ls1], S2};
+mapfold_1(_, S, []) ->
+    {[], S}.
+
+mapfold_2(F, S, [T | Ts]) ->
+    {T1, S1} = mapfold(F, S, T),
+    {Ts1, S2} = mapfold_2(F, S1, Ts),
+    {[T1 | Ts1], S2};
+mapfold_2(_, S, []) ->
+    {[], S}.
+
+
+%% =====================================================================
+%% @spec mapfold_subtrees(Function, Start::term(),
+%%                        Tree::syntaxTree()) -> {syntaxTree(), term()}
+%%
+%%          Function = (syntaxTree(), term()) -> {syntaxTree(), term()}
+%%
+%% @doc Does a mapfold operation over the immediate subtrees of a syntax
+%% tree. This is similar to `mapfold/3', but only on the
+%% immediate subtrees of `Tree', in left-to-right order; it
+%% does not include the root node of `Tree'.
+%%
+%% @see mapfold/3
+
+mapfold_subtrees(F, S, Tree) ->
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            {Tree, S};
+        Gs ->
+            {Gs1, S1} = mapfoldl_listlist(F, S, Gs),
+            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree), Gs1),
+            {erl_syntax:copy_attrs(Tree, Tree1), S1}
+    end.
+
+
+%% =====================================================================
+%% @spec mapfoldl_listlist(Function, State, [[term()]]) ->
+%%           {[[term()]], term()}
+%%
+%%          Function = (term(), term()) -> {term(), term()}
+%%
+%% @doc Like `lists:mapfoldl/3', but over a list of lists.
+%% The list of lists in the result has the same structure as the given
+%% list of lists.
+
+mapfoldl_listlist(F, S, [L | Ls]) ->
+    {L1, S1} = mapfoldl(F, S, L),
+    {Ls1, S2} = mapfoldl_listlist(F, S1, Ls),
+    {[L1 | Ls1], S2};
+mapfoldl_listlist(_, S, []) ->
+    {[], S}.
+
+mapfoldl(F, S, [L | Ls]) ->
+    {L1, S1} = F(L, S),
+    {Ls1, S2} = mapfoldl(F, S1, Ls),
+    {[L1 | Ls1], S2};
+mapfoldl(_, S, []) ->
+    {[], S}.
+
+
+%% =====================================================================
+%% @spec variables(syntaxTree()) -> set(atom())
+%%
+%%        set(T) = //stdlib/sets:set(T)
+%%
+%% @doc Returns the names of variables occurring in a syntax tree, The
+%% result is a set of variable names represented by atoms. Macro names
+%% are not included.
+%%
+%% @see //stdlib/sets
+
+variables(Tree) ->
+    variables(Tree, sets:new()).
+
+variables(T, S) ->
+    case erl_syntax:type(T) of
+	variable ->
+	    sets:add_element(erl_syntax:variable_name(T), S);
+	macro ->
+	    %% macro names are ignored, even if represented by variables
+	    case erl_syntax:macro_arguments(T) of
+		none -> S;
+		As ->
+		    variables_2(As, S)
+	    end;
+	_ ->
+	    case erl_syntax:subtrees(T) of
+		[] ->
+		    S;
+		Gs ->
+		    variables_1(Gs, S)
+	    end
+    end.
+
+variables_1([L | Ls], S) ->
+    variables_1(Ls, variables_2(L, S));
+variables_1([], S) ->
+    S.
+
+variables_2([T | Ts], S) ->
+    variables_2(Ts, variables(T, S));
+variables_2([], S) ->
+    S.
+
+
+-define(MINIMUM_RANGE, 100).
+-define(START_RANGE_FACTOR, 100).
+-define(MAX_RETRIES, 3).    % retries before enlarging range
+-define(ENLARGE_ENUM, 8).   % range enlargment enumerator
+-define(ENLARGE_DENOM, 1).  % range enlargment denominator
+
+default_variable_name(N) ->
+    list_to_atom("V" ++ integer_to_list(N)).
+
+%% =====================================================================
+%% @spec new_variable_name(Used::set(atom())) -> atom()
+%%
+%% @doc Returns an atom which is not already in the set `Used'. This is
+%% equivalent to `new_variable_name(Function, Used)', where `Function'
+%% maps a given integer `N' to the atom whose name consists of "`V'"
+%% followed by the numeral for `N'.
+%%
+%% @see new_variable_name/2
+
+new_variable_name(S) ->
+    new_variable_name(fun default_variable_name/1, S).
+
+%% =====================================================================
+%% @spec new_variable_name(Function, Used::set(atom())) -> atom()
+%%
+%%          Function = (integer()) -> atom()
+%%
+%% @doc Returns a user-named atom which is not already in the set
+%% `Used'. The atom is generated by applying the given
+%% `Function' to a generated integer. Integers are generated
+%% using an algorithm which tries to keep the names randomly distributed
+%% within a reasonably small range relative to the number of elements in
+%% the set.
+%%
+%% This function uses the module `random' to generate new
+%% keys. The seed it uses may be initialized by calling
+%% `random:seed/0' or `random:seed/3' before this
+%% function is first called.
+%%
+%% @see new_variable_name/1
+%% @see //stdlib/sets
+%% @see //stdlib/random
+
+new_variable_name(F, S) ->
+    R = start_range(S),
+    new_variable_name(R, F, S).
+
+new_variable_name(R, F, S) ->
+    new_variable_name(generate(R, R), R, 0, F, S).
+
+new_variable_name(N, R, T, F, S) when T < ?MAX_RETRIES ->
+    A = F(N),
+    case sets:is_element(A, S) of
+        true ->
+            new_variable_name(generate(N, R), R, T + 1, F, S);
+        false ->
+            A
+    end;
+new_variable_name(N, R, _T, F, S) ->
+    %% Too many retries - enlarge the range and start over.
+    R1 = (R * ?ENLARGE_ENUM) div ?ENLARGE_DENOM,
+    new_variable_name(generate(N, R1), R1, 0, F, S).
+
+%% Note that we assume that it is very cheap to take the size of
+%% the given set. This should be valid for the stdlib
+%% implementation of `sets'.
+
+start_range(S) ->
+    max(sets:size(S) * ?START_RANGE_FACTOR, ?MINIMUM_RANGE).
+
+max(X, Y) when X > Y -> X;
+max(_, Y) -> Y.
+
+%% The previous number might or might not be used to compute the
+%% next number to be tried. It is currently not used.
+%%
+%% It is important that this function does not generate values in
+%% order, but (pseudo-)randomly distributed over the range.
+
+generate(_Key, Range) ->
+    random:uniform(Range).    % works well
+
+
+%% =====================================================================
+%% @spec new_variable_names(N::integer(), Used::set(atom())) -> [atom()]
+%%
+%% @doc Like `new_variable_name/1', but generates a list of
+%% `N' new names.
+%% 
+%% @see new_variable_name/1
+
+new_variable_names(N, S) ->
+    new_variable_names(N, fun default_variable_name/1, S).
+
+%% =====================================================================
+%% @spec new_variable_names(N::integer(), Function,
+%%                          Used::set(atom())) -> [atom()]
+%%
+%%          Function = (integer()) -> atom()
+%%
+%% @doc Like `new_variable_name/2', but generates a list of
+%% `N' new names.
+%% 
+%% @see new_variable_name/2
+
+new_variable_names(N, F, S) when is_integer(N) ->
+    R = start_range(S),
+    new_variable_names(N, [], R, F, S).
+
+new_variable_names(N, Names, R, F, S) when N > 0 ->
+    Name = new_variable_name(R, F, S),
+    S1 = sets:add_element(Name, S),
+    new_variable_names(N - 1, [Name | Names], R, F, S1);
+new_variable_names(0, Names, _, _, _) ->
+    Names.
+
+
+%% =====================================================================
+%% @spec annotate_bindings(Tree::syntaxTree(),
+%%                         Bindings::ordset(atom())) -> syntaxTree()
+%%
+%% @type ordset(T) = //stdlib/ordsets:ordset(T)
+%%
+%% @doc Adds or updates annotations on nodes in a syntax tree.
+%% `Bindings' specifies the set of bound variables in the
+%% environment of the top level node. The following annotations are
+%% affected:
+%% <ul>
+%%     <li>`{env, Vars}', representing the input environment
+%%     of the subtree.</li>
+%%
+%%     <li>`{bound, Vars}', representing the variables that
+%%     are bound in the subtree.</li>
+%%
+%%     <li>`{free, Vars}', representing the free variables in
+%%     the subtree.</li>
+%% </ul>
+%% `Bindings' and `Vars' are ordered-set lists
+%% (cf. module `ordsets') of atoms representing variable
+%% names.
+%%
+%% @see annotate_bindings/1
+%% @see //stdlib/ordsets
+
+annotate_bindings(Tree, Env) ->
+    {Tree1, _, _} = vann(Tree, Env),
+    Tree1.
+
+%% =====================================================================
+%% @spec annotate_bindings(Tree::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Adds or updates annotations on nodes in a syntax tree.
+%% Equivalent to `annotate_bindings(Tree, Bindings)' where
+%% the top-level environment `Bindings' is taken from the
+%% annotation `{env, Bindings}' on the root node of
+%% `Tree'. An exception is thrown if no such annotation
+%% should exist.
+%%
+%% @see annotate_bindings/2
+
+annotate_bindings(Tree) ->
+    As = erl_syntax:get_ann(Tree),
+    case lists:keyfind(env, 1, As) of
+        {env, InVars} ->
+            annotate_bindings(Tree, InVars);
+        _ ->
+            erlang:error(badarg)
+    end.
+
+vann(Tree, Env) ->
+    case erl_syntax:type(Tree) of
+        variable ->
+            %% Variable use
+            Bound = [],
+            Free = [erl_syntax:variable_name(Tree)],
+            {ann_bindings(Tree, Env, Bound, Free), Bound, Free};
+        match_expr ->
+            vann_match_expr(Tree, Env);
+        case_expr ->
+            vann_case_expr(Tree, Env);
+        if_expr ->
+            vann_if_expr(Tree, Env);
+        cond_expr ->
+            vann_cond_expr(Tree, Env);
+        receive_expr ->
+            vann_receive_expr(Tree, Env);
+        catch_expr ->
+            vann_catch_expr(Tree, Env);
+        try_expr ->
+            vann_try_expr(Tree, Env);
+        function ->
+            vann_function(Tree, Env);
+        rule ->
+            vann_rule(Tree, Env);
+        fun_expr ->
+            vann_fun_expr(Tree, Env);
+        list_comp ->
+            vann_list_comp(Tree, Env);
+        binary_comp ->
+            vann_binary_comp(Tree, Env);
+        generator ->
+            vann_generator(Tree, Env);
+        binary_generator ->
+            vann_binary_generator(Tree, Env);
+        block_expr ->
+            vann_block_expr(Tree, Env);
+        macro ->
+            vann_macro(Tree, Env);
+        _Type ->
+            F = vann_list_join(Env),
+            {Tree1, {Bound, Free}} = mapfold_subtrees(F, {[], []},
+                                                      Tree),
+            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}
+    end.
+
+vann_list_join(Env) ->
+    fun (T, {Bound, Free}) ->
+            {T1, Bound1, Free1} = vann(T, Env),
+            {T1, {ordsets:union(Bound, Bound1),
+                  ordsets:union(Free, Free1)}}
+    end.
+
+vann_list(Ts, Env) ->
+    lists:mapfoldl(vann_list_join(Env), {[], []}, Ts).
+
+vann_function(Tree, Env) ->
+    Cs = erl_syntax:function_clauses(Tree),
+    {Cs1, {_, Free}} = vann_clauses(Cs, Env),
+    N = erl_syntax:function_name(Tree),
+    {N1, _, _} = vann(N, Env),
+    Tree1 = rewrite(Tree, erl_syntax:function(N1, Cs1)),
+    Bound = [],
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_rule(Tree, Env) ->
+    Cs = erl_syntax:rule_clauses(Tree),
+    {Cs1, {_, Free}} = vann_clauses(Cs, Env),
+    N = erl_syntax:rule_name(Tree),
+    {N1, _, _} = vann(N, Env),
+    Tree1 = rewrite(Tree, erl_syntax:rule(N1, Cs1)),
+    Bound = [],
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_fun_expr(Tree, Env) ->
+    Cs = erl_syntax:fun_expr_clauses(Tree),
+    {Cs1, {_, Free}} = vann_clauses(Cs, Env),
+    Tree1 = rewrite(Tree, erl_syntax:fun_expr(Cs1)),
+    Bound = [],
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_match_expr(Tree, Env) ->
+    E = erl_syntax:match_expr_body(Tree),
+    {E1, Bound1, Free1} = vann(E, Env),
+    Env1 = ordsets:union(Env, Bound1),
+    P = erl_syntax:match_expr_pattern(Tree),
+    {P1, Bound2, Free2} = vann_pattern(P, Env1),
+    Bound = ordsets:union(Bound1, Bound2),
+    Free = ordsets:union(Free1, Free2),
+    Tree1 = rewrite(Tree, erl_syntax:match_expr(P1, E1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_case_expr(Tree, Env) ->
+    E = erl_syntax:case_expr_argument(Tree),
+    {E1, Bound1, Free1} = vann(E, Env),
+    Env1 = ordsets:union(Env, Bound1),
+    Cs = erl_syntax:case_expr_clauses(Tree),
+    {Cs1, {Bound2, Free2}} = vann_clauses(Cs, Env1),
+    Bound = ordsets:union(Bound1, Bound2),
+    Free = ordsets:union(Free1, Free2),
+    Tree1 = rewrite(Tree, erl_syntax:case_expr(E1, Cs1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_if_expr(Tree, Env) ->
+    Cs = erl_syntax:if_expr_clauses(Tree),
+    {Cs1, {Bound, Free}} = vann_clauses(Cs, Env),
+    Tree1 = rewrite(Tree, erl_syntax:if_expr(Cs1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_cond_expr(_Tree, _Env) ->
+    erlang:error({not_implemented,cond_expr}).
+
+vann_catch_expr(Tree, Env) ->
+    E = erl_syntax:catch_expr_body(Tree),
+    {E1, _, Free} = vann(E, Env),
+    Tree1 = rewrite(Tree, erl_syntax:catch_expr(E1)),
+    Bound = [],
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_try_expr(Tree, Env) ->
+    Es = erl_syntax:try_expr_body(Tree),
+    {Es1, {Bound1, Free1}} = vann_body(Es, Env),
+    Cs = erl_syntax:try_expr_clauses(Tree),
+    %% bindings in the body should be available in the success case,
+    {Cs1, {_, Free2}} = vann_clauses(Cs, ordsets:union(Env, Bound1)),
+    Hs = erl_syntax:try_expr_handlers(Tree),
+    {Hs1, {_, Free3}} = vann_clauses(Hs, Env),
+    %% the after part does not export anything, yet; this might change
+    As = erl_syntax:try_expr_after(Tree),
+    {As1, {_, Free4}} = vann_body(As, Env),
+    Tree1 = rewrite(Tree, erl_syntax:try_expr(Es1, Cs1, Hs1, As1)),
+    Bound = [],
+    Free = ordsets:union(Free1, ordsets:union(Free2, ordsets:union(Free3, Free4))),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_receive_expr(Tree, Env) ->
+    %% The timeout action is treated as an extra clause.
+    %% Bindings in the expiry expression are local only.
+    Cs = erl_syntax:receive_expr_clauses(Tree),
+    Es = erl_syntax:receive_expr_action(Tree),
+    C = erl_syntax:clause([], Es),
+    {[C1 | Cs1], {Bound, Free1}} = vann_clauses([C | Cs], Env),
+    Es1 = erl_syntax:clause_body(C1),
+    {T1, _, Free2} = case erl_syntax:receive_expr_timeout(Tree) of
+                         none ->
+                             {none, [], []};
+                         T ->
+                             vann(T, Env)
+                     end,
+    Free = ordsets:union(Free1, Free2),
+    Tree1 = rewrite(Tree, erl_syntax:receive_expr(Cs1, T1, Es1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_list_comp(Tree, Env) ->
+    Es = erl_syntax:list_comp_body(Tree),
+    {Es1, {Bound1, Free1}} = vann_list_comp_body(Es, Env),
+    Env1 = ordsets:union(Env, Bound1),
+    T = erl_syntax:list_comp_template(Tree),
+    {T1, _, Free2} = vann(T, Env1),
+    Free = ordsets:union(Free1, ordsets:subtract(Free2, Bound1)),
+    Bound = [],
+    Tree1 = rewrite(Tree, erl_syntax:list_comp(T1, Es1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_list_comp_body_join() ->
+    fun (T, {Env, Bound, Free}) ->
+            {T1, Bound1, Free1} = case erl_syntax:type(T) of
+                                      binary_generator ->
+				          vann_binary_generator(T,Env);
+				      generator ->
+                                          vann_generator(T, Env);
+                                      _ ->
+                                          %% Bindings in filters are not
+                                          %% exported to the rest of the
+                                          %% body.
+                                          {T2, _, Free2} = vann(T, Env),
+                                          {T2, [], Free2}
+                                  end,
+            Env1 = ordsets:union(Env, Bound1),
+            {T1, {Env1, ordsets:union(Bound, Bound1),
+                  ordsets:union(Free, 
+                                ordsets:subtract(Free1, Bound))}}
+    end.
+
+vann_list_comp_body(Ts, Env) ->
+    F = vann_list_comp_body_join(),
+    {Ts1, {_, Bound, Free}} = lists:mapfoldl(F, {Env, [], []}, Ts),
+    {Ts1, {Bound, Free}}.
+
+vann_binary_comp(Tree, Env) ->
+    Es = erl_syntax:binary_comp_body(Tree),
+    {Es1, {Bound1, Free1}} = vann_binary_comp_body(Es, Env),
+    Env1 = ordsets:union(Env, Bound1),
+    T = erl_syntax:binary_comp_template(Tree),
+    {T1, _, Free2} = vann(T, Env1),
+    Free = ordsets:union(Free1, ordsets:subtract(Free2, Bound1)),
+    Bound = [],
+    Tree1 = rewrite(Tree, erl_syntax:binary_comp(T1, Es1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_binary_comp_body_join() ->
+    fun (T, {Env, Bound, Free}) ->
+            {T1, Bound1, Free1} = case erl_syntax:type(T) of
+                                    binary_generator ->
+				          vann_binary_generator(T, Env);
+				    generator ->
+                                          vann_generator(T, Env);
+                                      _ ->
+                                          %% Bindings in filters are not
+                                          %% exported to the rest of the
+                                          %% body.
+                                          {T2, _, Free2} = vann(T, Env),
+                                          {T2, [], Free2}
+                                  end,
+            Env1 = ordsets:union(Env, Bound1),
+            {T1, {Env1, ordsets:union(Bound, Bound1),
+                  ordsets:union(Free, 
+                                ordsets:subtract(Free1, Bound))}}
+    end.
+
+vann_binary_comp_body(Ts, Env) ->
+    F = vann_binary_comp_body_join(),
+    {Ts1, {_, Bound, Free}} = lists:mapfoldl(F, {Env, [], []}, Ts),
+    {Ts1, {Bound, Free}}.
+
+%% In list comprehension generators, the pattern variables are always
+%% viewed as new occurrences, shadowing whatever is in the input
+%% environment (thus, the pattern contains no variable uses, only
+%% bindings). Bindings in the generator body are not exported.
+
+vann_generator(Tree, Env) ->
+    P = erl_syntax:generator_pattern(Tree),
+    {P1, Bound, _} = vann_pattern(P, []),
+    E = erl_syntax:generator_body(Tree),
+    {E1, _, Free} = vann(E, Env),
+    Tree1 = rewrite(Tree, erl_syntax:generator(P1, E1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_binary_generator(Tree, Env) ->
+    P = erl_syntax:binary_generator_pattern(Tree),
+    {P1, Bound, _} = vann_pattern(P, Env),
+    E = erl_syntax:binary_generator_body(Tree),
+    {E1, _, Free} = vann(E, Env),
+    Tree1 = rewrite(Tree, erl_syntax:binary_generator(P1, E1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_block_expr(Tree, Env) ->
+    Es = erl_syntax:block_expr_body(Tree),
+    {Es1, {Bound, Free}} = vann_body(Es, Env),
+    Tree1 = rewrite(Tree, erl_syntax:block_expr(Es1)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_body_join() ->
+    fun (T, {Env, Bound, Free}) ->
+            {T1, Bound1, Free1} = vann(T, Env),
+            Env1 = ordsets:union(Env, Bound1),
+            {T1, {Env1, ordsets:union(Bound, Bound1),
+                  ordsets:union(Free,
+                                ordsets:subtract(Free1, Bound))}}
+    end.
+
+vann_body(Ts, Env) ->
+    {Ts1, {_, Bound, Free}} = lists:mapfoldl(vann_body_join(),
+                                             {Env, [], []}, Ts),
+    {Ts1, {Bound, Free}}.
+
+%% Macro names must be ignored even if they happen to be variables,
+%% lexically speaking.
+
+vann_macro(Tree, Env) ->
+    {As, {Bound, Free}} = case erl_syntax:macro_arguments(Tree) of
+                              none ->
+                                  {none, {[], []}};
+                              As1 ->
+                                  vann_list(As1, Env)
+                          end,
+    N = erl_syntax:macro_name(Tree),
+    Tree1 = rewrite(Tree, erl_syntax:macro(N, As)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_pattern(Tree, Env) ->
+    case erl_syntax:type(Tree) of
+        variable ->
+            V = erl_syntax:variable_name(Tree),
+            case ordsets:is_element(V, Env) of
+                true ->
+                    %% Variable use
+                    Bound = [],
+                    Free = [V],
+                    {ann_bindings(Tree, Env, Bound, Free), Bound, Free};
+                false ->
+                    %% Variable binding
+                    Bound = [V],
+                    Free = [],
+                    {ann_bindings(Tree, Env, Bound, Free), Bound, Free}
+            end;
+        match_expr ->
+            %% Alias pattern
+            P = erl_syntax:match_expr_pattern(Tree),
+            {P1, Bound1, Free1} = vann_pattern(P, Env),
+            E = erl_syntax:match_expr_body(Tree),
+            {E1, Bound2, Free2} = vann_pattern(E, Env),
+            Bound = ordsets:union(Bound1, Bound2),
+            Free = ordsets:union(Free1, Free2),
+            Tree1 = rewrite(Tree, erl_syntax:match_expr(P1, E1)),
+            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free};
+        macro ->
+            %% The macro name must be ignored. The arguments are treated
+            %% as patterns.
+            {As, {Bound, Free}} =
+                case erl_syntax:macro_arguments(Tree) of
+                    none ->
+                        {none, {[], []}};
+                    As1 ->
+                        vann_patterns(As1, Env)
+                end,
+            N = erl_syntax:macro_name(Tree),
+            Tree1 = rewrite(Tree, erl_syntax:macro(N, As)),
+            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free};
+        _Type ->
+            F = vann_patterns_join(Env),
+            {Tree1, {Bound, Free}} = mapfold_subtrees(F, {[], []},
+                                                      Tree),
+            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}
+    end.
+
+vann_patterns_join(Env) ->
+    fun (T, {Bound, Free}) ->
+            {T1, Bound1, Free1} = vann_pattern(T, Env),
+            {T1, {ordsets:union(Bound, Bound1),
+                  ordsets:union(Free, Free1)}}
+    end.
+
+vann_patterns(Ps, Env) ->
+    lists:mapfoldl(vann_patterns_join(Env), {[], []}, Ps).
+
+vann_clause(C, Env) ->
+    {Ps, {Bound1, Free1}} = vann_patterns(erl_syntax:clause_patterns(C),
+                                          Env),
+    Env1 = ordsets:union(Env, Bound1),
+    %% Guards cannot add bindings
+    {G1, _, Free2} = case erl_syntax:clause_guard(C) of
+                         none ->
+                             {none, [], []};
+                         G ->
+                             vann(G, Env1)
+                     end,
+    {Es, {Bound2, Free3}} = vann_body(erl_syntax:clause_body(C), Env1),
+    Bound = ordsets:union(Bound1, Bound2),
+    Free = ordsets:union(Free1,
+                         ordsets:subtract(ordsets:union(Free2, Free3),
+                                          Bound1)),
+    Tree1 = rewrite(C, erl_syntax:clause(Ps, G1, Es)),
+    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
+
+vann_clauses_join(Env) ->
+    fun (C, {Bound, Free}) ->
+            {C1, Bound1, Free1} = vann_clause(C, Env),
+            {C1, {ordsets:intersection(Bound, Bound1),
+                  ordsets:union(Free, Free1)}}
+    end.
+
+vann_clauses([C | Cs], Env) ->
+    {C1, Bound, Free} = vann_clause(C, Env),
+    {Cs1, BF} = lists:mapfoldl(vann_clauses_join(Env), {Bound, Free}, Cs),
+    {[C1 | Cs1], BF};
+vann_clauses([], _Env) ->
+    {[], {[], []}}.
+
+ann_bindings(Tree, Env, Bound, Free) ->
+    As0 = erl_syntax:get_ann(Tree),
+    As1 = [{env, Env},
+           {bound, Bound},
+           {free, Free}
+           | delete_binding_anns(As0)],
+    erl_syntax:set_ann(Tree, As1).
+
+delete_binding_anns([{env, _} | As]) ->
+    delete_binding_anns(As);
+delete_binding_anns([{bound, _} | As]) ->
+    delete_binding_anns(As);
+delete_binding_anns([{free, _} | As]) ->
+    delete_binding_anns(As);
+delete_binding_anns([A | As]) ->
+    [A | delete_binding_anns(As)];
+delete_binding_anns([]) ->
+    [].
+
+
+%% =====================================================================
+%% @spec is_fail_expr(Tree::syntaxTree()) -> bool()
+%%
+%% @doc Returns `true' if `Tree' represents an
+%% expression which never terminates normally. Note that the reverse
+%% does not apply. Currently, the detected cases are calls to
+%% `exit/1', `throw/1',
+%% `erlang:error/1' and `erlang:error/2'.
+%%
+%% @see //erts/erlang:exit/1
+%% @see //erts/erlang:throw/1
+%% @see //erts/erlang:error/1
+%% @see //erts/erlang:error/2
+
+is_fail_expr(E) ->          
+    case erl_syntax:type(E) of
+        application ->
+            N = length(erl_syntax:application_arguments(E)),
+            F = erl_syntax:application_operator(E),
+            case catch {ok, analyze_function_name(F)} of
+                syntax_error ->
+                    false;
+                {ok, exit} when N =:= 1 ->
+                    true;
+                {ok, throw} when N =:= 1 ->
+                    true;
+                {ok, {erlang, exit}} when N =:= 1 ->
+                    true;
+                {ok, {erlang, throw}} when N =:= 1 ->
+                    true;
+                {ok, {erlang, error}} when N =:= 1 ->
+                    true;
+                {ok, {erlang, error}} when N =:= 2 ->
+                    true;
+                {ok, {erlang, fault}} when N =:= 1 ->
+                    true;
+                {ok, {erlang, fault}} when N =:= 2 ->
+                    true;
+                _ ->
+                    false
+            end;
+        _ ->
+            false
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_forms(Forms) -> [{Key, term()}]
+%%
+%%          Forms = syntaxTree() | [syntaxTree()]
+%%          Key = attributes | errors | exports | functions | imports
+%%                | module | records | rules | warnings
+%%
+%% @doc Analyzes a sequence of "program forms". The given
+%% `Forms' may be a single syntax tree of type
+%% `form_list', or a list of "program form" syntax trees. The
+%% returned value is a list of pairs `{Key, Info}', where
+%% each value of `Key' occurs at most once in the list; the
+%% absence of a particular key indicates that there is no well-defined
+%% value for that key.
+%%
+%% Each entry in the resulting list contains the following
+%% corresponding information about the program forms:
+%% <dl>
+%%     <dt>`{attributes, Attributes}'</dt>
+%%       <dd><ul>
+%% 	   <li>`Attributes = [{atom(), term()}]'</li>
+%%       </ul>
+%% 	 `Attributes' is a list of pairs representing the
+%% 	 names and corresponding values of all so-called "wild"
+%% 	 attributes (as e.g. "`-compile(...)'") occurring in
+%% 	 `Forms' (cf. `analyze_wild_attribute/1').
+%% 	 We do not guarantee that each name occurs at most once in the
+%% 	 list. The order of listing is not defined.</dd>
+%%
+%%     <dt>`{errors, Errors}'</dt>
+%%       <dd><ul>
+%% 	   <li>`Errors = [term()]'</li>
+%%       </ul>
+%% 	 `Errors' is the list of error descriptors of all
+%% 	 `error_marker' nodes that occur in
+%% 	 `Forms'. The order of listing is not defined.</dd>
+%%
+%%     <dt>`{exports, Exports}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Exports = [FunctionName]'</li>
+%% 	    <li>`FunctionName = atom()
+%%                    | {atom(), integer()}
+%% 		      | {ModuleName, FunctionName}'</li>
+%% 	    <li>`ModuleName = atom()'</li>
+%%       </ul>
+%% 	 `Exports' is a list of representations of those
+%% 	 function names that are listed by export declaration attributes
+%% 	 in `Forms' (cf.
+%% 	 `analyze_export_attribute/1'). We do not guarantee
+%% 	 that each name occurs at most once in the list. The order of
+%% 	 listing is not defined.</dd>
+%%
+%%     <dt>`{functions, Functions}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Functions = [{atom(), integer()}]'</li>
+%%       </ul>
+%% 	 `Functions' is a list of the names of the functions
+%% 	 that are defined in `Forms' (cf.
+%% 	 `analyze_function/1'). We do not guarantee that each
+%% 	 name occurs at most once in the list. The order of listing is
+%% 	 not defined.</dd>
+%%
+%%     <dt>`{imports, Imports}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Imports = [{Module, Names}]'</li>
+%% 	    <li>`Module = atom()'</li>
+%% 	    <li>`Names = [FunctionName]'</li>
+%% 	    <li>`FunctionName = atom()
+%%                    | {atom(), integer()}
+%% 		      | {ModuleName, FunctionName}'</li>
+%% 	    <li>`ModuleName = atom()'</li>
+%%       </ul>
+%% 	 `Imports' is a list of pairs representing those
+%% 	 module names and corresponding function names that are listed
+%% 	 by import declaration attributes in `Forms' (cf.
+%% 	 `analyze_import_attribute/1'), where each
+%% 	 `Module' occurs at most once in
+%% 	 `Imports'. We do not guarantee that each name occurs
+%% 	 at most once in the lists of function names. The order of
+%% 	 listing is not defined.</dd>
+%%
+%%     <dt>`{module, ModuleName}'</dt>
+%%       <dd><ul>
+%% 	    <li>`ModuleName = atom()'</li>
+%%       </ul>
+%% 	 `ModuleName' is the name declared by a module
+%% 	 attribute in `Forms'. If no module name is defined
+%% 	 in `Forms', the result will contain no entry for the
+%% 	 `module' key. If multiple module name declarations
+%% 	 should occur, all but the first will be ignored.</dd>
+%%
+%%     <dt>`{records, Records}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Records = [{atom(), Fields}]'</li>
+%% 	    <li>`Fields = [{atom(), Default}]'</li>
+%% 	    <li>`Default = none | syntaxTree()'</li>
+%%       </ul>
+%% 	 `Records' is a list of pairs representing the names
+%% 	 and corresponding field declarations of all record declaration
+%% 	 attributes occurring in `Forms'. For fields declared
+%% 	 without a default value, the corresponding value for
+%% 	 `Default' is the atom `none' (cf.
+%% 	 `analyze_record_attribute/1'). We do not guarantee
+%% 	 that each record name occurs at most once in the list. The
+%% 	 order of listing is not defined.</dd>
+%%
+%%     <dt>`{rules, Rules}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Rules = [{atom(), integer()}]'</li>
+%%       </ul>
+%% 	 `Rules' is a list of the names of the rules that are
+%% 	 defined in `Forms' (cf.
+%% 	 `analyze_rule/1'). We do not guarantee that each
+%% 	 name occurs at most once in the list. The order of listing is
+%% 	 not defined.</dd>
+%%
+%%     <dt>`{warnings, Warnings}'</dt>
+%%       <dd><ul>
+%% 	    <li>`Warnings = [term()]'</li>
+%%       </ul>
+%% 	 `Warnings' is the list of error descriptors of all
+%% 	 `warning_marker' nodes that occur in
+%% 	 `Forms'. The order of listing is not defined.</dd>
+%% </dl>
+%%
+%% The evaluation throws `syntax_error' if an ill-formed
+%% Erlang construct is encountered.
+%%
+%% @see analyze_wild_attribute/1
+%% @see analyze_export_attribute/1
+%% @see analyze_import_attribute/1
+%% @see analyze_record_attribute/1
+%% @see analyze_function/1
+%% @see analyze_rule/1
+%% @see erl_syntax:error_marker_info/1
+%% @see erl_syntax:warning_marker_info/1
+
+analyze_forms(Forms) when is_list(Forms) ->
+    finfo_to_list(lists:foldl(fun collect_form/2, new_finfo(), Forms));
+analyze_forms(Forms) ->
+    analyze_forms(
+      erl_syntax:form_list_elements(
+        erl_syntax:flatten_form_list(Forms))).
+
+collect_form(Node, Info) ->
+    case analyze_form(Node) of
+        {attribute, {Name, Data}} ->
+            collect_attribute(Name, Data, Info);
+        {attribute, preprocessor} ->
+            Info;
+        {function, Name} ->
+            finfo_add_function(Name, Info);
+        {rule, Name} ->
+            finfo_add_rule(Name, Info);
+        {error_marker, Data} ->
+            finfo_add_error(Data, Info);
+        {warning_marker, Data} ->
+            finfo_add_warning(Data, Info);
+        _ ->
+            Info
+    end.
+
+collect_attribute(module, M, Info) ->
+    finfo_set_module(M, Info);
+collect_attribute(export, L, Info) ->
+    finfo_add_exports(L, Info);
+collect_attribute(import, {M, L}, Info) ->
+    finfo_add_imports(M, L, Info);
+collect_attribute(import, M, Info) ->
+    finfo_add_module_import(M, Info);
+collect_attribute(file, _, Info) ->
+    Info;
+collect_attribute(record, {R, L}, Info) ->
+    finfo_add_record(R, L, Info);
+collect_attribute(spec, _, Info) ->
+    Info;
+collect_attribute(_, {N, V}, Info) ->
+    finfo_add_attribute(N, V, Info).
+
+%% Abstract datatype for collecting module information.
+
+-record(forms, {module, exports, module_imports, imports, attributes,
+		records, errors, warnings, functions, rules}).
+
+new_finfo() ->
+    #forms{module = none,
+           exports = [],
+           module_imports = [],
+           imports = [],
+           attributes = [],
+           records = [],
+           errors = [],
+           warnings = [],
+           functions = [],
+           rules = []
+          }.
+
+finfo_set_module(Name, Info) ->
+    case Info#forms.module of
+        none ->
+            Info#forms{module = {value, Name}};
+        {value, _} ->
+            Info
+    end.
+
+finfo_add_exports(L, Info) ->
+    Info#forms{exports = L ++ Info#forms.exports}.
+
+finfo_add_module_import(M, Info) ->
+    Info#forms{module_imports = [M | Info#forms.module_imports]}.
+
+finfo_add_imports(M, L, Info) ->
+    Es = Info#forms.imports,
+    case lists:keyfind(M, 1, Es) of
+        {_, L1} ->
+            Es1 = lists:keyreplace(M, 1, Es, {M, L ++ L1}),
+            Info#forms{imports = Es1};
+        false ->
+            Info#forms{imports = [{M, L} | Es]}
+    end.
+
+finfo_add_attribute(Name, Val, Info) ->
+    Info#forms{attributes = [{Name, Val} | Info#forms.attributes]}.
+
+finfo_add_record(R, L, Info) ->
+    Info#forms{records = [{R, L} | Info#forms.records]}.
+
+finfo_add_error(R, Info) ->
+    Info#forms{errors = [R | Info#forms.errors]}.
+
+finfo_add_warning(R, Info) ->
+    Info#forms{warnings = [R | Info#forms.warnings]}.
+
+finfo_add_function(F, Info) ->
+    Info#forms{functions = [F | Info#forms.functions]}.
+
+finfo_add_rule(F, Info) ->
+    Info#forms{rules = [F | Info#forms.rules]}.
+
+finfo_to_list(Info) ->
+    [{Key, Value}
+     || {Key, {value, Value}} <-
+            [{module, Info#forms.module},
+             {exports, list_value(Info#forms.exports)},
+             {imports, list_value(Info#forms.imports)},
+             {module_imports, list_value(Info#forms.module_imports)},
+             {attributes, list_value(Info#forms.attributes)},
+             {records, list_value(Info#forms.records)},
+             {errors, list_value(Info#forms.errors)},
+             {warnings, list_value(Info#forms.warnings)},
+             {functions, list_value(Info#forms.functions)},
+             {rules, list_value(Info#forms.rules)}
+            ]].
+
+list_value([]) ->
+    none;
+list_value(List) ->
+    {value, List}.
+
+
+%% =====================================================================
+%% @spec analyze_form(Node::syntaxTree()) -> {atom(), term()} | atom()
+%%
+%% @doc Analyzes a "source code form" node. If `Node' is a
+%% "form" type (cf. `erl_syntax:is_form/1'), the returned
+%% value is a tuple `{Type, Info}' where `Type' is
+%% the node type and `Info' depends on `Type', as
+%% follows:
+%% <dl>
+%%   <dt>`{attribute, Info}'</dt>
+%%
+%%      <dd>where `Info = analyze_attribute(Node)'.</dd>
+%%
+%%   <dt>`{error_marker, Info}'</dt>
+%%
+%% 	<dd>where `Info =
+%% 	erl_syntax:error_marker_info(Node)'.</dd>
+%%
+%%   <dt>`{function, Info}'</dt>
+%%
+%% 	    <dd>where `Info = analyze_function(Node)'.</dd>
+%%
+%%   <dt>`{rule, Info}'</dt>
+%%
+%% 	    <dd>where `Info = analyze_rule(Node)'.</dd>
+%%
+%%   <dt>`{warning_marker, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    erl_syntax:warning_marker_info(Node)'.</dd>
+%% </dl>
+%% For other types of forms, only the node type is returned.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' is not well-formed.
+%%
+%% @see analyze_attribute/1
+%% @see analyze_function/1
+%% @see analyze_rule/1
+%% @see erl_syntax:is_form/1
+%% @see erl_syntax:error_marker_info/1
+%% @see erl_syntax:warning_marker_info/1
+
+analyze_form(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            {attribute, analyze_attribute(Node)};
+        function ->
+            {function, analyze_function(Node)};
+        rule ->
+            {rule, analyze_rule(Node)};
+        error_marker ->
+            {error_marker, erl_syntax:error_marker_info(Node)};
+        warning_marker ->
+            {warning_marker, erl_syntax:warning_marker_info(Node)};
+        _ ->
+            case erl_syntax:is_form(Node) of
+                true ->
+                    erl_syntax:type(Node);
+                false ->
+                    throw(syntax_error)
+            end
+    end.
+
+%% =====================================================================
+%% @spec analyze_attribute(Node::syntaxTree()) ->
+%%           preprocessor | {atom(), atom()}
+%%
+%% @doc Analyzes an attribute node. If `Node' represents a
+%% preprocessor directive, the atom `preprocessor' is
+%% returned. Otherwise, if `Node' represents a module
+%% attribute "`-<em>Name</em>...'", a tuple `{Name,
+%% Info}' is returned, where `Info' depends on
+%% `Name', as follows:
+%% <dl>
+%%     <dt>`{module, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    analyze_module_attribute(Node)'.</dd>
+%%
+%%     <dt>`{export, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    analyze_export_attribute(Node)'.</dd>
+%%
+%%     <dt>`{import, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    analyze_import_attribute(Node)'.</dd>
+%%
+%%     <dt>`{file, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    analyze_file_attribute(Node)'.</dd>
+%%
+%%     <dt>`{record, Info}'</dt>
+%%
+%% 	    <dd>where `Info =
+%% 	    analyze_record_attribute(Node)'.</dd>
+%%
+%%     <dt>`{Name, Info}'</dt>
+%%
+%% 	    <dd>where `{Name, Info} =
+%% 	    analyze_wild_attribute(Node)'.</dd>
+%% </dl>
+%% The evaluation throws `syntax_error' if `Node'
+%% does not represent a well-formed module attribute.
+%%
+%% @see analyze_module_attribute/1
+%% @see analyze_export_attribute/1
+%% @see analyze_import_attribute/1
+%% @see analyze_file_attribute/1
+%% @see analyze_record_attribute/1
+%% @see analyze_wild_attribute/1
+
+analyze_attribute(Node) ->
+    Name = erl_syntax:attribute_name(Node),
+    case erl_syntax:type(Name) of
+        atom ->
+            case erl_syntax:atom_value(Name) of
+                define -> preprocessor;
+                undef -> preprocessor;
+                include -> preprocessor;
+                include_lib -> preprocessor;
+                ifdef -> preprocessor;
+                ifndef -> preprocessor;
+                else -> preprocessor;
+                endif -> preprocessor;
+                A ->
+                    {A, analyze_attribute(A, Node)}
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+analyze_attribute(module, Node) ->
+    analyze_module_attribute(Node);
+analyze_attribute(export, Node) ->
+    analyze_export_attribute(Node);
+analyze_attribute(import, Node) ->
+    analyze_import_attribute(Node);
+analyze_attribute(file, Node) ->
+    analyze_file_attribute(Node);
+analyze_attribute(record, Node) ->
+    analyze_record_attribute(Node);
+analyze_attribute(define, _Node) ->
+    define;
+analyze_attribute(spec, _Node) ->
+    spec;
+analyze_attribute(_, Node) ->
+    %% A "wild" attribute (such as e.g. a `compile' directive).
+    analyze_wild_attribute(Node).
+
+
+%% =====================================================================
+%% @spec analyze_module_attribute(Node::syntaxTree()) ->
+%%           Name::atom() | {Name::atom(), Variables::[atom()]}
+%%
+%% @doc Returns the module name and possible parameters declared by a
+%% module attribute. If the attribute is a plain module declaration such
+%% as `-module(name)', the result is the module name. If the attribute
+%% is a parameterized module declaration, the result is a tuple
+%% containing the module name and a list of the parameter variable
+%% names.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed module
+%% attribute.
+%%
+%% @see analyze_attribute/1
+
+analyze_module_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            case erl_syntax:attribute_arguments(Node) of
+                [M] ->
+                    module_name_to_atom(M);
+                [M, L] ->
+		    M1 = module_name_to_atom(M),
+		    L1 = analyze_variable_list(L),
+		    {M1, L1};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+analyze_variable_list(Node) ->
+    case erl_syntax:is_proper_list(Node) of
+        true ->
+            [erl_syntax:variable_name(V)
+	     || V <- erl_syntax:list_elements(Node)];
+        false ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_export_attribute(Node::syntaxTree()) -> [FunctionName]
+%%
+%%          FunctionName = atom() | {atom(), integer()}
+%%                       | {ModuleName, FunctionName}
+%%          ModuleName = atom()
+%%
+%% @doc Returns the list of function names declared by an export
+%% attribute. We do not guarantee that each name occurs at most once in
+%% the list. The order of listing is not defined.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed export
+%% attribute.
+%%
+%% @see analyze_attribute/1
+
+analyze_export_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            case erl_syntax:attribute_arguments(Node) of
+                [L] ->
+                    analyze_function_name_list(L);
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+analyze_function_name_list(Node) ->
+    case erl_syntax:is_proper_list(Node) of
+        true ->
+            [analyze_function_name(F)
+             || F <- erl_syntax:list_elements(Node)];
+        false ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_function_name(Node::syntaxTree()) -> FunctionName
+%%
+%%          FunctionName = atom() | {atom(), integer()}
+%%                       | {ModuleName, FunctionName}
+%%          ModuleName = atom()
+%%
+%% @doc Returns the function name represented by a syntax tree. If
+%% `Node' represents a function name, such as
+%% "`foo/1'" or "`bloggs:fred/2'", a uniform
+%% representation of that name is returned. Different nestings of arity
+%% and module name qualifiers in the syntax tree does not affect the
+%% result.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed function name.
+
+analyze_function_name(Node) ->
+    case erl_syntax:type(Node) of
+        atom ->
+            erl_syntax:atom_value(Node);
+        arity_qualifier ->
+            A = erl_syntax:arity_qualifier_argument(Node),
+            case erl_syntax:type(A) of
+                integer ->
+                    F = erl_syntax:arity_qualifier_body(Node),
+                    F1 = analyze_function_name(F),
+                    append_arity(erl_syntax:integer_value(A), F1);
+                _ ->
+                    throw(syntax_error)
+            end;
+        module_qualifier ->
+            M = erl_syntax:module_qualifier_argument(Node),
+            case erl_syntax:type(M) of
+                atom ->
+                    F = erl_syntax:module_qualifier_body(Node),
+                    F1 = analyze_function_name(F),
+                    {erl_syntax:atom_value(M), F1};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+append_arity(A, {Module, Name}) ->
+    {Module, append_arity(A, Name)};
+append_arity(A, Name) when is_atom(Name) ->
+    {Name, A};
+append_arity(A, A) ->
+    A;
+append_arity(_A, Name) ->
+    Name.    % quietly drop extra arity in case of conflict
+
+
+%% =====================================================================
+%% @spec analyze_import_attribute(Node::syntaxTree()) ->
+%%           {atom(), [FunctionName]} | atom()
+%%
+%%          FunctionName = atom() | {atom(), integer()}
+%%                       | {ModuleName, FunctionName}
+%%          ModuleName = atom()
+%%
+%% @doc Returns the module name and (if present) list of function names
+%% declared by an import attribute. The returned value is an atom
+%% `Module' or a pair `{Module, Names}', where
+%% `Names' is a list of function names declared as imported
+%% from the module named by `Module'. We do not guarantee
+%% that each name occurs at most once in `Names'. The order
+%% of listing is not defined.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed import
+%% attribute.
+%%
+%% @see analyze_attribute/1
+
+analyze_import_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            case erl_syntax:attribute_arguments(Node) of
+		[M] ->
+		    module_name_to_atom(M);
+		[M, L] ->
+		    M1 = module_name_to_atom(M),
+		    L1 = analyze_function_name_list(L),
+		    {M1, L1};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_wild_attribute(Node::syntaxTree()) -> {atom(), term()}
+%%
+%% @doc Returns the name and value of a "wild" attribute. The result is
+%% the pair `{Name, Value}', if `Node' represents
+%% "`-Name(Value)'".
+%%
+%% Note that no checking is done whether `Name' is a
+%% reserved attribute name such as `module' or
+%% `export': it is assumed that the attribute is "wild".
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed wild
+%% attribute.
+%%
+%% @see analyze_attribute/1
+
+analyze_wild_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            N = erl_syntax:attribute_name(Node),
+            case erl_syntax:type(N) of
+                atom ->
+                    case erl_syntax:attribute_arguments(Node) of
+                        [V] ->
+			    case catch {ok, erl_syntax:concrete(V)} of
+				{ok, Val} ->
+				    {erl_syntax:atom_value(N), Val};
+				_ ->
+				    throw(syntax_error)
+			    end;
+                        _ ->
+                            throw(syntax_error)
+                    end;
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_record_attribute(Node::syntaxTree()) ->
+%%           {atom(), Fields}
+%%
+%%          Fields = [{atom(), none | syntaxTree()}]
+%%
+%% @doc Returns the name and the list of fields of a record declaration
+%% attribute. The result is a pair `{Name, Fields}', if
+%% `Node' represents "`-record(Name, {...}).'",
+%% where `Fields' is a list of pairs `{Label,
+%% Default}' for each field "`Label'" or "`Label =
+%% <em>Default</em>'" in the declaration, listed in left-to-right
+%% order. If the field has no default-value declaration, the value for
+%% `Default' will be the atom `none'. We do not
+%% guarantee that each label occurs at most one in the list.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed record declaration
+%% attribute.
+%%
+%% @see analyze_attribute/1
+%% @see analyze_record_field/1
+
+analyze_record_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            case erl_syntax:attribute_arguments(Node) of
+                [R, T] ->
+                    case erl_syntax:type(R) of
+                        atom ->
+                            Es = analyze_record_attribute_tuple(T),
+                            {erl_syntax:atom_value(R), Es};
+                        _ ->
+                            throw(syntax_error)
+                    end;
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+analyze_record_attribute_tuple(Node) ->
+    case erl_syntax:type(Node) of
+        tuple ->
+            [analyze_record_field(F)
+	     || F <- erl_syntax:tuple_elements(Node)];
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_record_expr(Node::syntaxTree()) ->
+%%     {atom(), Info} | atom()
+%%
+%%    Info = {atom(), [{atom(), Value}]} | {atom(), atom()} | atom()
+%%    Value = none | syntaxTree()
+%%
+%% @doc Returns the record name and field name/names of a record
+%% expression. If `Node' has type `record_expr',
+%% `record_index_expr' or `record_access', a pair
+%% `{Type, Info}' is returned, otherwise an atom
+%% `Type' is returned. `Type' is the node type of
+%% `Node', and `Info' depends on
+%% `Type', as follows:
+%% <dl>
+%%   <dt>`record_expr':</dt>
+%%     <dd>`{atom(), [{atom(), Value}]}'</dd>
+%%   <dt>`record_access':</dt>
+%%     <dd>`{atom(), atom()} | atom()'</dd>
+%%   <dt>`record_index_expr':</dt>
+%%     <dd>`{atom(), atom()}'</dd>
+%% </dl>
+%%
+%% For a `record_expr' node, `Info' represents
+%% the record name and the list of descriptors for the involved fields,
+%% listed in the order they appear. (See
+%% `analyze_record_field/1' for details on the field
+%% descriptors). For a `record_access' node,
+%% `Info' represents the record name and the field name (or
+%% if the record name is not included, only the field name; this is
+%% allowed only in Mnemosyne-query syntax). For a
+%% `record_index_expr' node, `Info' represents the
+%% record name and the name field name.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' represents a record expression that is not
+%% well-formed.
+%%
+%% @see analyze_record_attribute/1
+%% @see analyze_record_field/1
+
+analyze_record_expr(Node) ->
+    case erl_syntax:type(Node) of
+	record_expr ->
+            A = erl_syntax:record_expr_type(Node),
+            case erl_syntax:type(A) of
+                atom ->
+                    Fs = [analyze_record_field(F)
+			  || F <- erl_syntax:record_expr_fields(Node)],
+                    {record_expr, {erl_syntax:atom_value(A), Fs}};
+                _ ->
+                    throw(syntax_error)
+            end;
+	record_access ->
+	    F = erl_syntax:record_access_field(Node),
+	    case erl_syntax:type(F) of
+		atom ->
+		    case erl_syntax:record_access_type(Node) of
+			none ->
+			    {record_access, erl_syntax:atom_value(F)};
+			A ->
+			    case erl_syntax:type(A) of
+				atom ->
+				    {record_access,
+				     {erl_syntax:atom_value(A),
+				      erl_syntax:atom_value(F)}};
+				_ ->
+				    throw(syntax_error)
+			    end
+		    end;
+		_ ->
+		    throw(syntax_error)
+	    end;
+	record_index_expr ->
+	    F = erl_syntax:record_index_expr_field(Node),
+	    case erl_syntax:type(F) of
+		atom ->
+		    A = erl_syntax:record_index_expr_type(Node),
+		    case erl_syntax:type(A) of
+			atom ->
+			    {record_index_expr,
+			     {erl_syntax:atom_value(A),
+			      erl_syntax:atom_value(F)}};
+			_ ->
+			    throw(syntax_error)
+		    end;
+		_ ->
+		    throw(syntax_error)
+	    end;
+	Type ->
+	    Type
+    end.
+
+%% =====================================================================
+%% @spec analyze_record_field(Node::syntaxTree()) -> {atom(), Value}
+%%
+%%          Value = none | syntaxTree()
+%%
+%% @doc Returns the label and value-expression of a record field
+%% specifier. The result is a pair `{Label, Value}', if
+%% `Node' represents "`Label = <em>Value</em>'" or
+%% "`Label'", where in the first case, `Value' is
+%% a syntax tree, and in the second case `Value' is
+%% `none'.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed record field
+%% specifier.
+%%
+%% @see analyze_record_attribute/1
+%% @see analyze_record_expr/1
+
+analyze_record_field(Node) ->
+    case erl_syntax:type(Node) of
+        record_field ->
+            A = erl_syntax:record_field_name(Node),
+            case erl_syntax:type(A) of
+                atom ->
+                    T = erl_syntax:record_field_value(Node),
+                    {erl_syntax:atom_value(A), T};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_file_attribute(Node::syntaxTree()) ->
+%%           {string(), integer()}
+%%
+%% @doc Returns the file name and line number of a `file'
+%% attribute. The result is the pair `{File, Line}' if
+%% `Node' represents "`-file(File, Line).'".
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed `file'
+%% attribute.
+%%
+%% @see analyze_attribute/1
+
+analyze_file_attribute(Node) ->
+    case erl_syntax:type(Node) of
+        attribute ->
+            case erl_syntax:attribute_arguments(Node) of
+                [F, N] ->
+                    case (erl_syntax:type(F) =:= string)
+                        and (erl_syntax:type(N) =:= integer) of
+                        true ->
+                            {erl_syntax:string_value(F),
+                             erl_syntax:integer_value(N)};
+                        false ->
+                            throw(syntax_error)
+                    end;
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_function(Node::syntaxTree()) -> {atom(), integer()}
+%%
+%% @doc Returns the name and arity of a function definition. The result
+%% is a pair `{Name, A}' if `Node' represents a
+%% function definition "`Name(<em>P_1</em>, ..., <em>P_A</em>) ->
+%% ...'".
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed function
+%% definition.
+%%
+%% @see analyze_rule/1
+
+analyze_function(Node) ->
+    case erl_syntax:type(Node) of
+        function ->
+            N = erl_syntax:function_name(Node),
+            case erl_syntax:type(N) of
+                atom ->
+                    {erl_syntax:atom_value(N),
+                     erl_syntax:function_arity(Node)};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_rule(Node::syntaxTree()) -> {atom(), integer()}
+%%
+%% @doc Returns the name and arity of a Mnemosyne rule. The result is a
+%% pair `{Name, A}' if `Node' represents a rule
+%% "`Name(<em>P_1</em>, ..., <em>P_A</em>) :- ...'".
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed Mnemosyne
+%% rule.
+%%
+%% @see analyze_function/1
+
+analyze_rule(Node) ->
+    case erl_syntax:type(Node) of
+        rule ->
+            N = erl_syntax:rule_name(Node),
+            case erl_syntax:type(N) of
+                atom ->
+                    {erl_syntax:atom_value(N),
+                     erl_syntax:rule_arity(Node)};
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_implicit_fun(Node::syntaxTree()) -> FunctionName
+%%
+%%          FunctionName = atom() | {atom(), integer()}
+%%                       | {ModuleName, FunctionName}
+%%          ModuleName = atom()
+%%      
+%% @doc Returns the name of an implicit fun expression "`fun
+%% <em>F</em>'". The result is a representation of the function
+%% name `F'. (Cf. `analyze_function_name/1'.)
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed implicit fun.
+%%
+%% @see analyze_function_name/1
+
+analyze_implicit_fun(Node) ->
+    case erl_syntax:type(Node) of
+        implicit_fun ->
+            analyze_function_name(
+              erl_syntax:implicit_fun_name(Node));
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec analyze_application(Node::syntaxTree()) -> FunctionName | Arity
+%%
+%%          FunctionName = {atom(), Arity}
+%%                       | {ModuleName, FunctionName}
+%%          Arity = integer()
+%%          ModuleName = atom()
+%%
+%% @doc Returns the name of a called function. The result is a
+%% representation of the name of the applied function `F/A',
+%% if `Node' represents a function application
+%% "`<em>F</em>(<em>X_1</em>, ..., <em>X_A</em>)'". If the
+%% function is not explicitly named (i.e., `F' is given by
+%% some expression), only the arity `A' is returned.
+%%
+%% The evaluation throws `syntax_error' if
+%% `Node' does not represent a well-formed application
+%% expression.
+%%
+%% @see analyze_function_name/1
+
+analyze_application(Node) ->
+    case erl_syntax:type(Node) of
+        application ->
+            A = length(erl_syntax:application_arguments(Node)),
+            F = erl_syntax:application_operator(Node),
+            case catch {ok, analyze_function_name(F)} of
+                syntax_error ->
+                    A;
+                {ok, N} ->
+                    append_arity(A, N);
+                _ ->
+                    throw(syntax_error)
+            end;
+        _ ->
+            throw(syntax_error)
+    end.
+
+
+%% =====================================================================
+%% @spec function_name_expansions(Names::[Name]) -> [{ShortName, Name}]
+%%
+%%          Name = ShortName | {atom(), Name}
+%%          ShortName = atom() | {atom(), integer()}
+%%
+%% @doc Creates a mapping from corresponding short names to full
+%% function names. Names are represented by nested tuples of atoms and
+%% integers (cf. `analyze_function_name/1'). The result is a
+%% list containing a pair `{ShortName, Name}' for each
+%% element `Name' in the given list, where the corresponding
+%% `ShortName' is the rightmost-innermost part of
+%% `Name'. The list thus represents a finite mapping from
+%% unqualified names to the corresponding qualified names.
+%%
+%% Note: the resulting list can contain more than one tuple
+%% `{ShortName, Name}' for the same `ShortName',
+%% possibly with different values for `Name', depending on
+%% the given list.
+%%
+%% @see analyze_function_name/1
+
+function_name_expansions(Fs) ->
+    function_name_expansions(Fs, []).
+
+function_name_expansions([F | Fs], Ack) ->
+    function_name_expansions(Fs,
+                             function_name_expansions(F, F, Ack));
+function_name_expansions([], Ack) ->
+    Ack.
+
+function_name_expansions({A, N}, Name, Ack) when is_integer(N) ->
+    [{{A, N}, Name} | Ack];
+function_name_expansions({_, N}, Name, Ack) ->
+    function_name_expansions(N, Name,  Ack);
+function_name_expansions(A, Name, Ack) ->
+    [{A, Name} | Ack].
+
+
+%% =====================================================================
+%% @spec strip_comments(Tree::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Removes all comments from all nodes of a syntax tree. All other
+%% attributes (such as position information) remain unchanged.
+%% Standalone comments in form lists are removed; any other standalone
+%% comments are changed into null-comments (no text, no indentation).
+
+strip_comments(Tree) ->
+    map(fun strip_comments_1/1, Tree).
+
+strip_comments_1(T) ->
+    case erl_syntax:type(T) of
+	form_list ->
+	    Es = erl_syntax:form_list_elements(T),
+	    Es1 = [E || E <- Es, erl_syntax:type(E) /= comment],
+	    T1 = erl_syntax:copy_attrs(T, erl_syntax:form_list(Es1)),
+	    erl_syntax:remove_comments(T1);
+	comment ->
+	    erl_syntax:comment([]);
+	_ ->
+	    erl_syntax:remove_comments(T)
+    end.
+
+%% =====================================================================
+%% @spec to_comment(Tree) -> syntaxTree()
+%% @equiv to_comment(Tree, "% ")
+
+to_comment(Tree) ->
+    to_comment(Tree, "% ").
+
+%% =====================================================================
+%% @spec to_comment(Tree::syntaxTree(), Prefix::string()) ->
+%%           syntaxTree()
+%%
+%% @doc Equivalent to `to_comment(Tree, Prefix, F)' for a
+%% default formatting function `F'. The default
+%% `F' simply calls `erl_prettypr:format/1'.
+%%
+%% @see to_comment/3
+%% @see erl_prettypr:format/1
+
+to_comment(Tree, Prefix) ->
+    F = fun (T) -> erl_prettypr:format(T) end,
+    to_comment(Tree, Prefix, F).
+
+%% =====================================================================
+%% @spec to_comment(Tree::syntaxTree(), Prefix::string(), Printer) ->
+%%           syntaxTree()
+%%
+%%          Printer = (syntaxTree()) -> string()
+%%
+%% @doc Transforms a syntax tree into an abstract comment. The lines of
+%% the comment contain the text for `Node', as produced by
+%% the given `Printer' function. Each line of the comment is
+%% prefixed by the string `Prefix' (this does not include the
+%% initial "`%'" character of the comment line).
+%%
+%% For example, the result of
+%% `to_comment(erl_syntax:abstract([a,b,c]))' represents
+%% <pre>
+%%         %% [a,b,c]</pre>
+%% (cf. `to_comment/1').
+%%
+%% Note: the text returned by the formatting function will be split
+%% automatically into separate comment lines at each line break. No
+%% extra work is needed.
+%%
+%% @see to_comment/1
+%% @see to_comment/2
+
+to_comment(Tree, Prefix, F) ->
+    erl_syntax:comment(split_lines(F(Tree), Prefix)).
+
+
+%% =====================================================================
+%% @spec limit(Tree, Depth) -> syntaxTree()
+%%
+%% @doc Equivalent to `limit(Tree, Depth, Text)' using the
+%% text `"..."' as default replacement.
+%%
+%% @see limit/3
+%% @see erl_syntax:text/1
+
+limit(Tree, Depth) ->
+    limit(Tree, Depth, erl_syntax:text("...")).
+
+%% =====================================================================
+%% @spec limit(Tree::syntaxTree(), Depth::integer(),
+%%             Node::syntaxTree()) -> syntaxTree()
+%%
+%% @doc Limits a syntax tree to a specified depth. Replaces all non-leaf
+%% subtrees in `Tree' at the given `Depth' by
+%% `Node'. If `Depth' is negative, the result is
+%% always `Node', even if `Tree' has no subtrees.
+%%
+%% When a group of subtrees (as e.g., the argument list of an
+%% `application' node) is at the specified depth, and there
+%% are two or more subtrees in the group, these will be collectively
+%% replaced by `Node' even if they are leaf nodes. Groups of
+%% subtrees that are above the specified depth will be limited in size,
+%% as if each subsequent tree in the group were one level deeper than
+%% the previous. E.g., if `Tree' represents a list of
+%% integers "`[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]'", the result
+%% of `limit(Tree, 5)' will represent `[1, 2, 3, 4,
+%% ...]'.
+%%
+%% The resulting syntax tree is typically only useful for
+%% pretty-printing or similar visual formatting.
+%%
+%% @see limit/2
+
+limit(_Tree, Depth, Node) when Depth < 0 ->
+    Node;
+limit(Tree, Depth, Node) ->
+    limit_1(Tree, Depth, Node).
+
+limit_1(Tree, Depth, Node) ->
+    %% Depth is nonnegative here.
+    case erl_syntax:subtrees(Tree) of
+        [] ->
+            if Depth > 0 ->
+                    Tree;
+               true ->
+                    case is_simple_leaf(Tree) of
+                        true ->
+                            Tree;
+                        false ->
+                            Node
+                    end
+            end;
+        Gs ->
+            if Depth > 1 ->
+                    Gs1 = [[limit_1(T, Depth - 1, Node)
+                            || T <- limit_list(G, Depth, Node)]
+                           || G <- Gs],
+                    rewrite(Tree,
+                            erl_syntax:make_tree(erl_syntax:type(Tree),
+                                                 Gs1));
+               Depth =:= 0 ->
+                    %% Depth is zero, and this is not a leaf node
+                    %% so we always replace it.
+                    Node;
+               true ->
+                    %% Depth is 1, so all subtrees are to be cut.
+                    %% This is done groupwise.
+                    Gs1 = [cut_group(G, Node) || G <- Gs],
+                    rewrite(Tree,
+                            erl_syntax:make_tree(erl_syntax:type(Tree),
+                                                 Gs1))
+            end
+    end.
+
+cut_group([], _Node) ->
+    [];
+cut_group([T], Node) ->
+    %% Only if the group contains a single subtree do we try to
+    %% preserve it if suitable.
+    [limit_1(T, 0, Node)];
+cut_group(_Ts, Node) ->
+    [Node].
+
+is_simple_leaf(Tree) ->
+    case erl_syntax:type(Tree) of
+        atom -> true;
+        char -> true;
+        float -> true;
+        integer -> true;
+        nil -> true;
+        operator -> true;
+        tuple -> true;
+        underscore -> true;
+        variable -> true;
+        _ -> false
+    end.
+
+%% If list has more than N elements, take the N - 1 first and
+%% append Node; otherwise return list as is.
+
+limit_list(Ts, N, Node) ->
+    if length(Ts) > N ->
+            limit_list_1(Ts, N - 1, Node);
+       true ->
+            Ts
+    end.
+
+limit_list_1([T | Ts], N, Node) ->
+    if N > 0 ->
+            [T | limit_list_1(Ts, N - 1, Node)];
+       true ->
+            [Node]
+    end;
+limit_list_1([], _N, _Node) ->
+    [].
+
+
+%% =====================================================================
+%% Utility functions
+
+rewrite(Tree, Tree1) ->
+    erl_syntax:copy_attrs(Tree, Tree1).
+
+module_name_to_atom(M) ->
+    case erl_syntax:type(M) of
+	atom ->
+	    erl_syntax:atom_value(M);
+	qualified_name ->
+	    list_to_atom(packages:concat(
+			   [erl_syntax:atom_value(A)
+			    || A <- erl_syntax:qualified_name_segments(M)])
+			);
+	_ ->
+	    throw(syntax_error)
+    end.
+
+%% This splits lines at line terminators and expands tab characters to
+%% spaces. The width of a tab is assumed to be 8.
+
+% split_lines(Cs) ->
+%     split_lines(Cs, "").
+
+split_lines(Cs, Prefix) ->
+    split_lines(Cs, Prefix, 0).
+
+split_lines(Cs, Prefix, N) ->
+    lists:reverse(split_lines(Cs, N, [], [], Prefix)).
+
+split_lines([$\r, $\n | Cs], _N, Cs1, Ls, Prefix) ->
+    split_lines_1(Cs, Cs1, Ls, Prefix);
+split_lines([$\r | Cs], _N, Cs1, Ls, Prefix) ->
+    split_lines_1(Cs, Cs1, Ls, Prefix);
+split_lines([$\n | Cs], _N, Cs1, Ls, Prefix) ->
+    split_lines_1(Cs, Cs1, Ls, Prefix);
+split_lines([$\t | Cs], N, Cs1, Ls, Prefix) ->
+    split_lines(Cs, 0, push(8 - (N rem 8), $\040, Cs1), Ls,
+                Prefix);
+split_lines([C | Cs], N, Cs1, Ls, Prefix) ->
+    split_lines(Cs, N + 1, [C | Cs1], Ls, Prefix);
+split_lines([], _, [], Ls, _) ->
+    Ls;
+split_lines([], _N, Cs, Ls, Prefix) ->
+    [Prefix ++ lists:reverse(Cs) | Ls].
+
+split_lines_1(Cs, Cs1, Ls, Prefix) ->
+    split_lines(Cs, 0, [], [Prefix ++ lists:reverse(Cs1) | Ls],
+                Prefix).
+
+push(N, C, Cs) when N > 0 ->
+    push(N - 1, C, [C | Cs]);
+push(0, _, Cs) ->
+    Cs.
+
diff --git a/lib/syntax_tools/src/erl_tidy.erl b/lib/syntax_tools/src/erl_tidy.erl
new file mode 100644
index 0000000000..e3b479008f
--- /dev/null
+++ b/lib/syntax_tools/src/erl_tidy.erl
@@ -0,0 +1,1898 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or
+%% modify it under the terms of the GNU Lesser General Public License
+%% as published by the Free Software Foundation; either version 2 of
+%% the License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1999-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Tidies and pretty-prints Erlang source code, removing unused
+%% functions, updating obsolete constructs and function calls, etc.
+%%
+%% Caveats: It is possible that in some intricate uses of macros,
+%% the automatic addition or removal of parentheses around uses or
+%% arguments could cause the resulting program to be rejected by the
+%% compiler; however, we have found no such case in existing
+%% code. Programs defining strange macros can usually not be read by
+%% this program, and in those cases, no changes will be made.
+%%
+%% If you really, really want to, you may call it "Inga".
+%%
+%% Disclaimer: The author accepts no responsibility for errors
+%% introduced in code that has been processed by the program. It has
+%% been reasonably well tested, but the possibility of errors remains.
+%% Keep backups of your original code safely stored, until you feel
+%% confident that the new, modified code can be trusted.
+
+-module(erl_tidy).
+
+-export([dir/0, dir/1, dir/2, file/1, file/2, module/1, module/2]).
+
+-include_lib("kernel/include/file.hrl").
+
+-define(DEFAULT_BACKUP_SUFFIX, ".bak").
+-define(DEFAULT_DIR, "").
+-define(DEFAULT_REGEXP, ".*\\.erl$").
+
+%% =====================================================================
+
+-type options()  :: [atom() | {atom(), any()}].
+
+%% =====================================================================
+
+dir__defaults() ->
+    [{follow_links, false},
+     recursive,
+     {regexp, ?DEFAULT_REGEXP},
+     verbose].
+
+%% =====================================================================
+%% @spec dir() -> ok
+%% @equiv dir("")
+
+-spec dir() -> 'ok'.
+dir() ->
+    dir("").
+
+%% =====================================================================
+%% @spec dir(Dir) -> ok
+%% @equiv dir(Dir, [])
+
+-spec dir(file:filename()) -> 'ok'.
+dir(Dir) ->
+    dir(Dir, []).
+
+%% =====================================================================
+%% @spec dir(Directory::filename(), Options::[term()]) -> ok
+%%           filename() = file:filename()
+%%
+%% @doc Tidies Erlang source files in a directory and its
+%% subdirectories.
+%%
+%% Available options:
+%% <dl>
+%%   <dt>{follow_links, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', symbolic directory
+%%       links will be followed.  The default value is
+%%       `false'.</dd>
+%%
+%%   <dt>{recursive, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', subdirectories will be
+%%       visited recursively.  The default value is
+%%       `true'.</dd>
+%%
+%%   <dt>{regexp, string()}</dt>
+%%
+%%       <dd>The value denotes a regular expression (see module
+%%       `regexp').  Tidying will only be applied to those
+%%       regular files whose names match this pattern. The default
+%%       value is `".*\\.erl$"', which matches normal
+%%       Erlang source file names.</dd>
+%%
+%%   <dt>{test, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', no files will be
+%%       modified. The default value is `false'.</dd>
+%%
+%%   <dt>{verbose, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', progress messages will
+%%       be output while the program is running, unless the
+%%       `quiet' option is `true'. The default
+%%       value when calling {@link dir/2} is `true'.</dd>
+%%
+%% </dl>
+%%
+%% See the function {@link file/2} for further options.
+%%
+%% @see //stdlib/regexp
+%% @see file/2
+
+-record(dir, {follow_links = false :: boolean(),
+	      recursive    = true  :: boolean(),
+	      options              :: options()}).
+
+-spec dir(file:filename(), options()) -> 'ok'.
+dir(Dir, Opts) ->
+    Opts1 = Opts ++ dir__defaults(),
+    Env = #dir{follow_links = proplists:get_bool(follow_links, Opts1),
+               recursive = proplists:get_bool(recursive, Opts1),
+               options = Opts1},
+    Regexp = proplists:get_value(regexp, Opts1),
+    case filename(Dir) of
+        "" ->
+            Dir1 = ".";
+        Dir1 ->
+            ok
+    end,
+    dir_1(Dir1, Regexp, Env).
+
+dir_1(Dir, Regexp, Env) ->
+    case file:list_dir(Dir) of
+        {ok, Files} ->
+            lists:foreach(fun (X) -> dir_2(X, Regexp, Dir, Env) end,
+                          Files);
+        {error, _} ->
+            report_error("error reading directory `~s'",
+                         [filename(Dir)]),
+            exit(error)
+    end.
+
+dir_2(Name, Regexp, Dir, Env) ->
+    File = if Dir =:= "" ->
+                   Name;
+              true ->
+                   filename:join(Dir, Name)
+           end,
+    case file_type(File) of
+        {value, regular} ->
+            dir_4(File, Regexp, Env);
+        {value, directory} when Env#dir.recursive =:= true ->
+            case is_symlink(Name) of
+                false ->
+                    dir_3(Name, Dir, Regexp, Env);
+                true when Env#dir.follow_links =:= true ->
+                    dir_3(Name, Dir, Regexp, Env);
+                _ ->
+                    ok
+            end;
+        _ ->
+            ok
+    end.
+
+dir_3(Name, Dir, Regexp, Env) ->
+    Dir1 = filename:join(Dir, Name),
+    verbose("tidying directory `~s'.", [Dir1], Env#dir.options),
+    dir_1(Dir1, Regexp, Env).
+
+dir_4(File, Regexp, Env) ->
+    case re:run(File, Regexp) of
+        {match, _} ->
+            Opts = [{outfile, File}, {dir, ""} | Env#dir.options],
+            case catch file(File, Opts) of
+                {'EXIT', Value} ->
+                    warn("error tidying `~s'.~n~p", [File,Value], Opts);
+                _ ->
+                    ok
+            end;
+        nomatch ->
+            ok
+    end.
+
+file__defaults() ->
+    [{backup_suffix, ?DEFAULT_BACKUP_SUFFIX},
+     backups, 
+     {dir, ?DEFAULT_DIR},
+     {printer, default_printer()},
+     {quiet, false},
+     {verbose, false}].
+
+default_printer() ->
+    fun (Tree, Options) -> erl_prettypr:format(Tree, Options) end.
+
+%% =====================================================================
+%% @spec file(Name) -> ok
+%% @equiv file(Name, [])
+
+-spec file(file:filename()) -> 'ok'.
+file(Name) ->
+    file(Name, []).
+
+%% =====================================================================
+%% @spec file(Name::filename(), Options::[term()]) -> ok
+%%
+%% @doc Tidies an Erlang source code file.
+%%
+%% Available options are:
+%% <dl>
+%%   <dt>{backup_suffix, string()}</dt>
+%%
+%%       <dd>Specifies the file name suffix to be used when a backup
+%%       file is created; the default value is `".bak"'
+%%       (cf. the `backups' option).</dd>
+%%
+%%   <dt>{backups, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', existing files will be
+%%       renamed before new files are opened for writing. The new
+%%       names are formed by appending the string given by the
+%%       `backup_suffix' option to the original name. The
+%%       default value is `true'.</dd>
+%%
+%%   <dt>{dir, filename()}</dt>
+%%
+%%       <dd>Specifies the name of the directory in which the output
+%%       file is to be written. By default, the current directory is
+%%       used. If the value is an empty string, the current directory
+%%       is used. </dd>
+%%
+%%   <dt>{outfile, filename()}</dt>
+%%
+%%       <dd>Specifies the name of the file (without suffix) to which
+%%       the resulting source code is to be written. If this option is
+%%       not specified, the `Name' argument is used.</dd>
+%%
+%%   <dt>{printer, Function}</dt>
+%%       <dd><ul>
+%%         <li>`Function = (syntaxTree()) -> string()'</li>
+%%       </ul>
+%%
+%%       Specifies a function for prettyprinting Erlang syntax trees.
+%%       This is used for outputting the resulting module definition.
+%%       The function is assumed to return formatted text for the given
+%%       syntax tree, and should raise an exception if an error occurs.
+%%       The default formatting function calls
+%%       `erl_prettypr:format/2'.</dd>
+%%
+%%   <dt>{test, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', no files will be modified; this
+%%       is typically most useful if the `verbose' flag is enabled, to
+%%       generate reports about the program files without affecting
+%%       them. The default value is `false'.</dd>
+%% </dl>
+%%
+%% See the function `module/2' for further options.
+%%
+%% @see erl_prettypr:format/2
+%% @see module/2
+
+-spec file(file:filename(), options()) -> 'ok'.
+file(Name, Opts) ->
+    Parent = self(),
+    Child = spawn_link(fun () -> file_1(Parent, Name, Opts) end),
+    receive
+        {Child, ok} ->
+            ok;
+        {Child, {error, Reason}} ->
+            exit(Reason)
+    end.
+
+file_1(Parent, Name, Opts) ->
+    try file_2(Name, Opts) of
+	_ ->
+	    Parent ! {self(), ok}
+    catch
+	throw:syntax_error ->       % ignore syntax errors
+	    Parent ! {self(), ok};
+	error:Reason ->
+	    Parent ! {self(), {error, Reason}}
+    end.
+
+file_2(Name, Opts) ->
+    Opts1 = Opts ++ file__defaults(),
+    Forms = read_module(Name, Opts1),
+    Comments = erl_comment_scan:file(Name),
+    Forms1 = erl_recomment:recomment_forms(Forms, Comments),
+    Tree = module(Forms1, [{file, Name} | Opts1]),
+    case proplists:get_bool(test, Opts1) of
+        true ->
+            ok;
+        false ->
+            write_module(Tree, Name, Opts1),
+            ok
+    end.
+
+read_module(Name, Opts) ->
+    verbose("reading module `~s'.", [filename(Name)], Opts),
+    case epp_dodger:parse_file(Name, [no_fail]) of
+        {ok, Forms} ->
+            check_forms(Forms, Name),
+            Forms;
+        {error, R} ->
+            error_read_file(Name),
+            exit({error, R})
+    end.
+
+check_forms(Fs, Name) ->
+    Fun = fun (F) ->
+                  case erl_syntax:type(F) of
+                      error_marker ->
+                          S = case erl_syntax:error_marker_info(F) of
+                                  {_, M, D} ->
+                                      M:format_error(D);
+                                  _ ->
+                                      "unknown error"
+                              end,
+                          report_error({Name, erl_syntax:get_pos(F),
+                                        "\n  ~s"}, [S]),
+                          exit(error);
+                      _ ->
+                          ok
+                  end
+          end,
+    lists:foreach(Fun, Fs).
+
+%% Create the target directory and make a backup file if necessary,
+%% then open the file, output the text and close the file
+%% safely. Returns the file name.
+
+write_module(Tree, Name, Opts) ->
+    Name1 = proplists:get_value(outfile, Opts, filename(Name)),
+    Dir = filename(proplists:get_value(dir, Opts, "")),
+    File = if Dir =:= "" ->
+                   Name1;
+              true ->
+                   case file_type(Dir) of
+                       {value, directory} ->
+                           ok;
+                       {value, _} ->
+                           report_error("`~s' is not a directory.",
+                                        [filename(Dir)]),
+                           exit(error);
+                       none ->
+                           case file:make_dir(Dir) of
+                               ok ->
+                                   verbose("created directory `~s'.",
+                                           [filename(Dir)], Opts),
+                                   ok;
+                               E ->
+                                   report_error("failed to create "
+                                                "directory `~s'.",
+                                                [filename(Dir)]),
+                                   exit({make_dir, E})
+                           end
+                   end,
+                   filename(filename:join(Dir, Name1))
+           end,
+    case proplists:get_bool(backups, Opts) of
+        true ->
+            backup_file(File, Opts);
+        false ->
+            ok
+    end,
+    Printer = proplists:get_value(printer, Opts),
+    FD = open_output_file(File),
+    verbose("writing to file `~s'.", [File], Opts),
+    V = (catch {ok, output(FD, Printer, Tree, Opts)}),
+    ok = file:close(FD),
+    case V of
+        {ok, _} ->
+            File;
+        {'EXIT', R} ->
+            error_write_file(File),
+            exit(R);
+        R ->
+            error_write_file(File),
+            throw(R)
+    end.
+
+output(FD, Printer, Tree, Opts) ->
+    io:put_chars(FD, Printer(Tree, Opts)),
+    io:nl(FD).
+
+%% file_type(file:filename()) -> {value, Type} | none
+
+file_type(Name) ->
+    file_type(Name, false).
+
+is_symlink(Name) ->
+    file_type(Name, true) =:= {value, symlink}.
+
+file_type(Name, Links) ->
+    V = case Links of
+            true ->
+                catch file:read_link_info(Name);
+            false ->
+                catch file:read_file_info(Name)
+        end,
+    case V of
+        {ok, Env} ->
+            {value, Env#file_info.type};
+        {error, enoent} ->
+            none;
+        {error, R} ->
+            error_read_file(Name),
+            exit({error, R});
+        {'EXIT', R} ->
+            error_read_file(Name),
+            exit(R);
+        R ->
+            error_read_file(Name),
+            throw(R)
+    end.
+
+open_output_file(FName) ->
+    case catch file:open(FName, [write]) of
+        {ok, FD} ->
+            FD;
+        {error, R} ->
+            error_open_output(FName),
+            exit({error, R});
+        {'EXIT', R} ->
+            error_open_output(FName),
+            exit(R);
+        R ->
+            error_open_output(FName),
+            exit(R)
+    end.
+
+%% If the file exists, rename it by appending the given suffix to the
+%% file name.
+
+backup_file(Name, Opts) ->
+    case file_type(Name) of
+        {value, regular} ->
+            backup_file_1(Name, Opts);
+        {value, _} ->
+            error_backup_file(Name),
+            exit(error);
+        none ->
+            ok
+    end.
+
+%% The file should exist and be a regular file here.
+
+backup_file_1(Name, Opts) ->
+    Suffix = proplists:get_value(backup_suffix, Opts, ""),
+    Dest = filename:join(filename:dirname(Name),
+                         filename:basename(Name) ++ Suffix),
+    case catch file:rename(Name, Dest) of
+        ok ->
+            verbose("made backup of file `~s'.", [Name], Opts);
+        {error, R} ->
+            error_backup_file(Name),
+            exit({error, R});
+        {'EXIT', R} ->
+            error_backup_file(Name),
+            exit(R);
+        R ->
+            error_backup_file(Name),
+            throw(R)
+    end.
+
+
+%% =====================================================================
+%% @spec module(Forms) -> syntaxTree()
+%% @equiv module(Forms, [])
+
+module(Forms) ->
+    module(Forms, []).
+
+%% =====================================================================
+%% @spec module(Forms, Options::[term()]) -> syntaxTree()
+%%
+%%          Forms = syntaxTree() | [syntaxTree()]
+%%          syntaxTree() = erl_syntax:syntaxTree()
+%%
+%% @doc Tidies a syntax tree representation of a module
+%% definition. The given `Forms' may be either a single
+%% syntax tree of type `form_list', or a list of syntax
+%% trees representing "program forms". In either case,
+%% `Forms' must represent a single complete module
+%% definition. The returned syntax tree has type
+%% `form_list' and represents a tidied-up version of the
+%% same source code.
+%%
+%% Available options are:
+%% <dl>
+%%   <dt>{auto_export_vars, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', all matches
+%%       "`{V1, ..., Vn} = E'" where `E' is a
+%%       case-, if- or receive-expression whose branches all return
+%%       n-tuples (or explicitly throw exceptions) will be rewritten
+%%       to bind and export the variables `V1', ...,
+%%       `Vn' directly. The default value is `false'.
+%%
+%%       For example:
+%%       <pre>
+%%                {X, Y} = case ... of
+%%                             ... -> {17, foo()};
+%%                             ... -> {42, bar()}
+%%                         end
+%%       </pre>
+%%       will be rewritten to:
+%%       <pre>
+%%                case ... of
+%%                    ... -> X = 17, Y = foo(), {X, Y};
+%%                    ... -> X = 42, Y = bar(), {X, Y}
+%%                end
+%%       </pre></dd>
+%%
+%%   <dt>{auto_list_comp, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', calls to `lists:map/2' and
+%%       `lists:filter/2' will be rewritten using list comprehensions.
+%%       The default value is `true'.</dd>
+%%
+%%   <dt>{file, string()}</dt>
+%%
+%%       <dd>Specifies the name of the file from which the source code
+%%       was taken. This is only used for generation of error
+%%       reports. The default value is the empty string.</dd>
+%%
+%%   <dt>{idem, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', all options that affect how the
+%%       code is modified are set to "no changes". For example, to
+%%       only update guard tests, and nothing else, use the options
+%%       `[new_guard_tests, idem]'. (Recall that options closer to the
+%%       beginning of the list have higher precedence.)</dd>
+%%
+%%   <dt>{keep_unused, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', unused functions will
+%%       not be removed from the code. The default value is
+%%       `false'.</dd>
+%%
+%%   <dt>{new_guard_tests, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', guard tests will be updated to
+%%       use the new names, e.g. "`is_integer(X)'" instead of
+%%       "`integer(X)'". The default value is `true'. See also
+%%       `old_guard_tests'.</dd>
+%%
+%%   <dt>{no_imports, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', all import statements will be
+%%       removed and calls to imported functions will be expanded to
+%%       explicit remote calls. The default value is `false'.</dd>
+%%
+%%   <dt>{old_guard_tests, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', guard tests will be changed to
+%%       use the old names instead of the new ones, e.g.
+%%       "`integer(X)'" instead of "`is_integer(X)'". The default
+%%       value is `false'. This option overrides the `new_guard_tests'
+%%       option.</dd>
+%%
+%%   <dt>{quiet, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', all information
+%%       messages and warning messages will be suppressed. The default
+%%       value is `false'.</dd>
+%%
+%%   <dt>{rename, [{{atom(), atom(), integer()},
+%%                  {atom(), atom()}}]}</dt>
+%%
+%%       <dd>The value is a list of pairs, associating tuples
+%%       `{Module, Name, Arity}' with tuples `{NewModule, NewName}',
+%%       specifying renamings of calls to remote functions. By
+%%       default, the value is the empty list.
+%%
+%%       The renaming affects only remote calls (also when
+%%       disguised by import declarations); local calls within a
+%%       module are not affected, and no function definitions are
+%%       renamed. Since the arity cannot change, the new name is
+%%       represented by `{NewModule, NewName}' only. Only
+%%       calls matching the specified arity will match; multiple
+%%       entries are necessary for renaming calls to functions that
+%%       have the same module and function name, but different
+%%       arities.
+%%
+%%       This option can also be used to override the default
+%%       renaming of calls which use obsolete function names.</dd>
+%%
+%%   <dt>{verbose, boolean()}</dt>
+%%
+%%       <dd>If the value is `true', progress messages will be output
+%%       while the program is running, unless the `quiet' option is
+%%       `true'. The default value is `false'.</dd>
+%%
+%% </dl>
+
+module(Forms, Opts) when is_list(Forms) ->
+    module(erl_syntax:form_list(Forms), Opts);
+module(Forms, Opts) ->
+    Opts1 = proplists:expand(module__expansions(), Opts)
+	    ++ module__defaults(),
+    File = proplists:get_value(file, Opts1, ""),
+    Forms1 = erl_syntax:flatten_form_list(Forms),
+    module_1(Forms1, File, Opts1).
+
+module__defaults() ->
+    [{auto_export_vars, false},
+     {auto_list_comp, true},
+     {keep_unused, false},
+     {new_guard_tests, true},
+     {no_imports, false},
+     {old_guard_tests, false},
+     {quiet, false},
+     {verbose, false}].
+
+module__expansions() ->
+    [{idem, [{auto_export_vars, false},
+	     {auto_list_comp, false},
+	     {keep_unused, true},
+	     {new_guard_tests, false},
+	     {no_imports, false},
+	     {old_guard_tests, false}]}].
+
+module_1(Forms, File, Opts) ->
+    Info = analyze_forms(Forms, File),
+    Module = get_module_name(Info, File),
+    Attrs = get_module_attributes(Info),
+    Exports = get_module_exports(Info),
+    Imports = get_module_imports(Info),
+    Opts1 = check_imports(Imports, Opts, File),
+    Fs = erl_syntax:form_list_elements(Forms),
+    {Names, Defs} = collect_functions(Fs),
+    Exports1 = check_export_all(Attrs, Names, Exports),
+    Roots = ordsets:union(ordsets:from_list(Exports1),
+                          hidden_uses(Fs, Imports)),
+    {Names1, Used, Imported, Defs1} = visit_used(Names, Defs, Roots,
+                                                 Imports, Module,
+                                                 Opts1),
+    Fs1 = update_forms(Fs, Defs1, Imported, Opts1),
+    Fs2 = filter_forms(Fs1, Names1, Used, Opts1),
+    rewrite(Forms, erl_syntax:form_list(Fs2)).
+
+analyze_forms(Forms, File) ->
+    case catch {ok, erl_syntax_lib:analyze_forms(Forms)} of
+        {ok, L1} ->
+            L1;
+        syntax_error ->
+            report_error({File, 0, "syntax error."}),
+	    throw(syntax_error);
+        {'EXIT', R} ->
+            exit(R);
+        R ->
+            throw(R)
+    end.
+
+%% XXX: The following should be imported from erl_syntax_lib
+-type key()       :: atom().
+-type info_pair() :: {key(), any()}.
+
+-spec get_module_name([info_pair()], string()) -> atom().
+get_module_name(List, File) ->
+    case lists:keyfind(module, 1, List) of
+        {module, M} ->
+            M;
+        _ ->
+            report_error({File, 0,
+                          "cannot determine module name."}),
+            exit(error)
+    end.
+
+get_module_attributes(List) ->
+    case lists:keyfind(attributes, 1, List) of
+        {attributes, As} ->
+            As;
+        _ ->
+            []
+    end.
+
+-spec get_module_exports([info_pair()]) -> [{atom(), byte()}].
+get_module_exports(List) ->
+    case lists:keyfind(exports, 1, List) of
+        {exports, Es} ->
+            Es;
+        _ ->
+            []
+    end.
+
+-spec get_module_imports([info_pair()]) -> [{atom(), atom()}].
+get_module_imports(List) ->
+    case lists:keyfind(imports, 1, List) of
+        {imports, Is} ->
+            flatten_imports(Is);
+        _ ->
+            []
+    end.
+
+compile_attrs(As) ->
+    lists:append([if is_list(T) -> T; true -> [T] end
+                  || {compile, T} <- As]).
+
+-spec flatten_imports([{atom(), [atom()]}]) -> [{atom(), atom()}].
+flatten_imports(Is) ->
+    [{F, M} || {M, Fs} <- Is, F <- Fs].
+
+check_imports(Is, Opts, File) ->
+    case check_imports_1(lists:sort(Is)) of
+        true ->
+            Opts;
+        false ->
+            case proplists:get_bool(no_imports, Opts) of
+                true ->
+                    warn({File, 0,
+			  "conflicting import declarations - "
+			  "will not expand imports."},
+			 [], Opts),
+                    %% prevent expansion of imports
+                    [{no_imports, false} | Opts];
+                false ->
+                    Opts
+            end
+    end.
+
+-spec check_imports_1([{atom(), atom()}]) -> boolean().
+check_imports_1([{F1, M1}, {F2, M2} | _Is]) when F1 =:= F2, M1 =/= M2 ->
+    false;
+check_imports_1([_ | Is]) ->
+    check_imports_1(Is);
+check_imports_1([]) ->
+    true.
+
+check_export_all(Attrs, Names, Exports) ->
+    case lists:member(export_all, compile_attrs(Attrs)) of
+        true ->
+            Exports ++ sets:to_list(Names);
+        false ->
+            Exports
+    end.
+
+filter_forms(Fs, Names, Used, Opts) ->
+    Keep = case proplists:get_bool(keep_unused, Opts) of
+               true ->
+                   Names;
+               false ->
+                   Used
+           end,
+    [F || F <- Fs, keep_form(F, Keep, Opts)].
+
+keep_form(Form, Used, Opts) ->
+    case erl_syntax:type(Form) of
+        function ->
+            N = erl_syntax_lib:analyze_function(Form),
+            case sets:is_element(N, Used) of
+                false ->
+                    report_removed_def("function", N, Form, Opts),
+                    false;
+                true ->
+                    true
+            end;
+        rule ->
+            N = erl_syntax_lib:analyze_rule(Form),
+            case sets:is_element(N, Used) of
+                false ->
+                    report_removed_def("rule", N, Form, Opts),
+                    false;
+                true ->
+                    true
+            end;
+        attribute ->
+            case erl_syntax_lib:analyze_attribute(Form) of
+                {file, _} ->
+                    false;
+                _ ->
+                    true
+            end;
+        error_marker ->
+            false;
+        warning_marker ->
+            false;
+        eof_marker ->
+            false;
+        _ ->
+            true
+    end.
+
+report_removed_def(Type, {N, A}, Form, Opts) ->
+    File = proplists:get_value(file, Opts, ""),
+    report({File, erl_syntax:get_pos(Form),
+	    "removing unused ~s `~w/~w'."},
+	   [Type, N, A], Opts).
+
+collect_functions(Forms) ->
+    lists:foldl(
+      fun (F, {Names, Defs}) ->
+              case erl_syntax:type(F) of
+                  function ->
+                      N = erl_syntax_lib:analyze_function(F),
+                      {sets:add_element(N, Names),
+                       dict:store(N, {F, []}, Defs)};
+                  rule ->
+                      N = erl_syntax_lib:analyze_rule(F),
+                      {sets:add_element(N, Names),
+                       dict:store(N, {F, []}, Defs)};
+                  _ ->
+                      {Names, Defs}
+              end
+      end,
+      {sets:new(), dict:new()},
+      Forms).
+
+update_forms([F | Fs], Defs, Imports, Opts) ->
+    case erl_syntax:type(F) of
+        function ->
+            N = erl_syntax_lib:analyze_function(F),
+            {F1, Fs1} = dict:fetch(N, Defs),
+            [F1 | lists:reverse(Fs1)] ++ update_forms(Fs, Defs, Imports,
+                                                      Opts);
+        rule ->
+            N = erl_syntax_lib:analyze_rule(F),
+            {F1, Fs1} = dict:fetch(N, Defs),
+            [F1 | lists:reverse(Fs1)] ++ update_forms(Fs, Defs, Imports,
+                                                      Opts);
+        attribute ->
+            [update_attribute(F, Imports, Opts)
+             | update_forms(Fs, Defs, Imports, Opts)];
+        _ ->
+            [F | update_forms(Fs, Defs, Imports, Opts)]
+    end;
+update_forms([], _, _, _) ->
+    [].
+
+update_attribute(F, Imports, Opts) ->
+    case erl_syntax_lib:analyze_attribute(F) of
+        {import, {M, Ns}} ->
+            Ns1 = ordsets:from_list([N || N <- Ns,
+                                          sets:is_element(N, Imports)]),
+            case ordsets:subtract(ordsets:from_list(Ns), Ns1) of
+                [] ->
+                    ok;
+                Names ->
+                    File = proplists:get_value(file, Opts, ""),
+                    report({File, erl_syntax:get_pos(F),
+			    "removing unused imports:~s"},
+			   [[io_lib:fwrite("\n\t`~w:~w/~w'", [M, N, A])
+			     || {N, A} <- Names]], Opts)
+            end,
+            Is = [make_fname(N) || N <- Ns1],
+            if Is =:= [] ->
+                    %% This will be filtered out later.
+                    erl_syntax:warning_marker(deleted);
+               true ->
+                    F1 = erl_syntax:attribute(erl_syntax:atom(import),
+                                              [erl_syntax:atom(M),
+                                               erl_syntax:list(Is)]),
+                    rewrite(F, F1)
+            end;
+        {export, Ns} ->
+            Es = [make_fname(N) || N <- ordsets:from_list(Ns)],
+            F1 = erl_syntax:attribute(erl_syntax:atom(export),
+                                      [erl_syntax:list(Es)]),
+            rewrite(F, F1);
+        _ ->
+            F
+    end.
+
+make_fname({F, A}) ->
+    erl_syntax:arity_qualifier(erl_syntax:atom(F),
+                               erl_syntax:integer(A)).
+
+hidden_uses(Fs, Imports) ->
+    Used = lists:foldl(fun (F, S) ->
+                               case erl_syntax:type(F) of
+                                   attribute ->
+                                       hidden_uses_1(F, S);
+                                   _ ->
+                                       S
+                               end
+                       end,
+                       [], Fs),
+    ordsets:subtract(Used, ordsets:from_list([F || {F, _M} <- Imports])).
+
+hidden_uses_1(Tree, Used) ->
+    erl_syntax_lib:fold(fun hidden_uses_2/2, Used, Tree).
+
+hidden_uses_2(Tree, Used) ->
+    case erl_syntax:type(Tree) of
+        application ->
+            F = erl_syntax:application_operator(Tree),
+            case erl_syntax:type(F) of
+                atom ->
+                    As = erl_syntax:application_arguments(Tree),
+                    N = {erl_syntax:atom_value(F), length(As)},
+                    case is_auto_imported(N) of
+                        true ->
+                            Used;
+                        false ->
+                            ordsets:add_element(N, Used)
+                    end;
+                _ ->
+                    Used
+            end;
+        implicit_fun ->
+            F = erl_syntax:implicit_fun_name(Tree),
+            case catch {ok, erl_syntax_lib:analyze_function_name(F)} of
+                {ok, {Name, Arity} = N}
+                when is_atom(Name), is_integer(Arity) ->
+                    ordsets:add_element(N, Used);
+                _ ->
+                    Used
+            end;
+        _ ->
+            Used
+    end.
+
+-type context() :: 'guard_expr' | 'guard_test' | 'normal'.
+
+-record(env, {file		       :: file:filename(),
+              module,
+              current,
+              imports,
+              context = normal	       :: context(),
+              verbosity = 1	       :: 0 | 1 | 2,
+              quiet = false            :: boolean(),
+              no_imports = false       :: boolean(),
+              spawn_funs = false       :: boolean(),
+              auto_list_comp = true    :: boolean(),
+              auto_export_vars = false :: boolean(),
+              new_guard_tests = true   :: boolean(),
+	      old_guard_tests = false  :: boolean()}).
+
+-record(st, {varc, used, imported, vars, functions, new_forms, rename}).
+
+visit_used(Names, Defs, Roots, Imports, Module, Opts) ->
+    File = proplists:get_value(file, Opts, ""),
+    NoImports = proplists:get_bool(no_imports, Opts),
+    Rename = proplists:append_values(rename, Opts),
+    loop(Roots, sets:new(), Defs,
+         #env{file = File,
+              module = Module,
+              imports = dict:from_list(Imports),
+              verbosity = verbosity(Opts),
+              no_imports = NoImports,
+              spawn_funs = proplists:get_bool(spawn_funs, Opts),
+              auto_list_comp = proplists:get_bool(auto_list_comp, Opts),
+              auto_export_vars = proplists:get_bool(auto_export_vars,
+						    Opts),
+              new_guard_tests = proplists:get_bool(new_guard_tests,
+						   Opts),
+              old_guard_tests = proplists:get_bool(old_guard_tests,
+						   Opts)},
+         #st{used = sets:from_list(Roots),
+             imported = sets:new(),
+             functions = Names,
+             rename = dict:from_list([X || {F1, F2} = X <- Rename,
+                                           is_remote_name(F1),
+                                           is_atom_pair(F2)])}).
+
+loop([F | Work], Seen0, Defs0, Env, St0) ->
+    case sets:is_element(F, Seen0) of
+        true ->
+            loop(Work, Seen0, Defs0, Env, St0);
+        false ->
+            Seen1 = sets:add_element(F, Seen0),
+            case dict:find(F, Defs0) of
+                {ok, {Form, Fs}} ->
+                    Vars = erl_syntax_lib:variables(Form),
+                    Form1 = erl_syntax_lib:annotate_bindings(Form, []),
+                    {Form2, St1} = visit(Form1, Env#env{current = F},
+                                         St0#st{varc = 1,
+                                                used = sets:new(),
+                                                vars = Vars,
+                                                new_forms = []}),
+                    Fs1 = St1#st.new_forms ++ Fs,
+                    Defs1 = dict:store(F, {Form2, Fs1}, Defs0),
+                    Used = St1#st.used,
+                    Work1 = sets:to_list(Used) ++ Work,
+                    St2 = St1#st{used = sets:union(Used, St0#st.used)},
+                    loop(Work1, Seen1, Defs1, Env, St2);
+                error ->
+                    %% Quietly ignore any names that have no definition.
+                    loop(Work, Seen1, Defs0, Env, St0)
+            end
+    end;
+loop([], _, Defs, _, St) ->
+    {St#st.functions, St#st.used, St#st.imported, Defs}.
+
+visit(Tree, Env, St0) ->
+    case erl_syntax:type(Tree) of
+        application ->
+            visit_application(Tree, Env, St0);
+        infix_expr ->
+            visit_infix_expr(Tree, Env, St0);
+        prefix_expr ->
+            visit_prefix_expr(Tree, Env, St0);
+        implicit_fun ->
+            visit_implicit_fun(Tree, Env, St0);
+        clause ->
+            visit_clause(Tree, Env, St0);
+        list_comp ->
+            visit_list_comp(Tree, Env, St0);
+        match_expr ->
+            visit_match_expr(Tree, Env, St0);
+        _ ->
+            visit_other(Tree, Env, St0)
+    end.
+
+visit_other(Tree, Env, St) ->
+    F = fun (T, S) -> visit(T, Env, S) end,
+    erl_syntax_lib:mapfold_subtrees(F, St, Tree).
+
+visit_list(Ts, Env, St0) ->
+    lists:mapfoldl(fun (T, S) -> visit(T, Env, S) end, St0, Ts).
+
+visit_implicit_fun(Tree, _Env, St0) ->
+    F = erl_syntax:implicit_fun_name(Tree),
+    case catch {ok, erl_syntax_lib:analyze_function_name(F)} of
+        {ok, {Name, Arity} = N}
+        when is_atom(Name), is_integer(Arity) ->
+            Used = sets:add_element(N, St0#st.used),
+            {Tree, St0#st{used = Used}};
+        _ ->
+	    %% symbolic funs do not count as uses of a function
+            {Tree, St0}
+    end.
+
+visit_clause(Tree, Env, St0) ->
+    %% We do not visit the patterns (for now, anyway).
+    Ps = erl_syntax:clause_patterns(Tree),
+    {G, St1} = case erl_syntax:clause_guard(Tree) of
+                   none ->
+                       {none, St0};
+                   G0 ->
+                       visit(G0, Env#env{context = guard_test}, St0)
+               end,
+    {B, St2} = visit_list(erl_syntax:clause_body(Tree), Env, St1),
+    {rewrite(Tree, erl_syntax:clause(Ps, G, B)), St2}.
+
+visit_infix_expr(Tree, #env{context = guard_test}, St0) ->
+    %% Detect transition from guard test to guard expression.
+    visit_other(Tree, #env{context = guard_expr}, St0);
+visit_infix_expr(Tree, Env, St0) ->
+    visit_other(Tree, Env, St0).
+
+visit_prefix_expr(Tree, #env{context = guard_test}, St0) ->
+    %% Detect transition from guard test to guard expression.
+    visit_other(Tree, #env{context = guard_expr}, St0);
+visit_prefix_expr(Tree, Env, St0) ->
+    visit_other(Tree, Env, St0).
+
+visit_application(Tree, Env, St0) ->
+    Env1 = case Env of
+               #env{context = guard_test} ->
+                   Env#env{context = guard_expr};
+               _ ->
+                   Env
+           end,
+    {F, St1} = visit(erl_syntax:application_operator(Tree), Env1, St0),
+    {As, St2} = visit_list(erl_syntax:application_arguments(Tree), Env1,
+                           St1),
+    case erl_syntax:type(F) of
+        atom ->
+            visit_atom_application(F, As, Tree, Env, St2);
+        implicit_fun ->
+            visit_named_fun_application(F, As, Tree, Env, St2);
+        fun_expr ->
+            visit_lambda_application(F, As, Tree, Env, St2);
+        _ ->
+            visit_nonlocal_application(F, As, Tree, Env, St2)
+    end.
+
+visit_application_final(F, As, Tree, St0) ->
+    {rewrite(Tree, erl_syntax:application(F, As)), St0}.
+
+revisit_application(F, As, Tree, Env, St0) ->
+    visit(rewrite(Tree, erl_syntax:application(F, As)), Env, St0).
+
+visit_atom_application(F, As, Tree, #env{context = guard_test} = Env,
+                       St0) ->
+    N = erl_syntax:atom_value(F),
+    A = length(As),
+    N1 = case Env#env.old_guard_tests of
+             true ->
+                 reverse_guard_test(N, A);
+             false ->
+		 case Env#env.new_guard_tests of
+		     true ->
+			 rewrite_guard_test(N, A);
+		     false ->
+			 N
+		 end
+	 end,
+    if N1 =/= N ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "changing guard test `~w' to `~w'."},
+		   [N, N1], Env#env.verbosity);
+       true ->
+            ok
+    end,
+    %% No need to revisit here.
+    F1 = rewrite(F, erl_syntax:atom(N1)),
+    visit_application_final(F1, As, Tree, St0);
+visit_atom_application(F, As, Tree, #env{context = guard_expr}, St0) ->
+    %% Atom applications in guard expressions are never local calls.
+    visit_application_final(F, As, Tree, St0);
+visit_atom_application(F, As, Tree, Env, St0) ->
+    N = {erl_syntax:atom_value(F), length(As)},
+    case is_auto_imported(N) of
+        true ->
+            visit_bif_call(N, F, As, Tree, Env, St0);
+        false ->
+            case is_imported(N, Env) of
+                true ->
+                    visit_import_application(N, F, As, Tree, Env, St0);
+                false ->
+                    Used = sets:add_element(N, St0#st.used),
+                    visit_application_final(F, As, Tree,
+                                            St0#st{used = Used})
+            end
+    end.
+
+visit_import_application({N, A} = Name, F, As, Tree, Env, St0) ->
+    M = dict:fetch(Name, Env#env.imports),
+    Expand = case Env#env.no_imports of
+                 true ->
+                     true;
+                 false ->
+                     auto_expand_import({M, N, A}, St0)
+             end,
+    case Expand of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "expanding call to imported function `~w:~w/~w'."},
+		   [M, N, A], Env#env.verbosity),
+            F1 = erl_syntax:module_qualifier(erl_syntax:atom(M),
+                                             erl_syntax:atom(N)),
+            revisit_application(rewrite(F, F1), As, Tree, Env, St0);
+        false ->
+            Is = sets:add_element(Name, St0#st.imported),
+            visit_application_final(F, As, Tree, St0#st{imported = Is})
+    end.
+
+visit_bif_call({apply, 2}, F, [E, Args] = As, Tree, Env, St0) ->
+    case erl_syntax:is_proper_list(Args) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "changing use of `apply/2' "
+		    "to direct function call."},
+		   [], Env#env.verbosity),
+            As1 = erl_syntax:list_elements(Args),
+            revisit_application(E, As1, Tree, Env, St0);
+        false ->
+            visit_application_final(F, As, Tree, St0)
+    end;
+visit_bif_call({apply, 3}, F, [M, N, Args] = As, Tree, Env, St0) ->
+    case erl_syntax:is_proper_list(Args) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "changing use of `apply/3' "
+		    "to direct remote call."},
+		   [], Env#env.verbosity),
+            F1 = rewrite(F, erl_syntax:module_qualifier(M, N)),
+            As1 = erl_syntax:list_elements(Args),
+            visit_nonlocal_application(F1, As1, Tree, Env, St0);
+        false ->
+            visit_application_final(F, As, Tree, St0)
+    end;
+visit_bif_call({spawn, 3} = N, F, [_, _, _] = As, Tree, Env, St0) ->
+    visit_spawn_call(N, F, [], As, Tree, Env, St0);
+visit_bif_call({spawn_link, 3} = N, F, [_, _, _] = As, Tree, Env,
+               St0) ->
+    visit_spawn_call(N, F, [], As, Tree, Env, St0);
+visit_bif_call({spawn, 4} = N, F, [A | [_, _, _] = As], Tree, Env,
+               St0) ->
+    visit_spawn_call(N, F, [A], As, Tree, Env, St0);
+visit_bif_call({spawn_link, 4} = N, F, [A | [_, _, _] = As], Tree, Env,
+               St0) ->
+    visit_spawn_call(N, F, [A], As, Tree, Env, St0);
+visit_bif_call(_, F, As, Tree, _Env, St0) ->
+    visit_application_final(F, As, Tree, St0).
+
+visit_spawn_call({N, A}, F, Ps, [A1, A2, A3] = As, Tree,
+                 #env{spawn_funs = true} = Env, St0) ->
+    case erl_syntax:is_proper_list(A3) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "changing use of `~w/~w' to `~w/~w' with a fun."},
+		   [N, A, N, 1 + length(Ps)], Env#env.verbosity),
+            F1 = case erl_syntax:is_atom(A1, Env#env.module) of
+                     true ->
+                         A2;    % calling self
+                     false ->
+                         clone(A1,
+                               erl_syntax:module_qualifier(A1, A2))
+                 end,
+            %% Need to do some scoping tricks here to make sure the
+            %% arguments are evaluated by the parent, not by the spawned
+            %% process.
+            As1 = erl_syntax:list_elements(A3),
+            {Vs, St1} = new_variables(length(As1), St0),
+            E1 = clone(F1, erl_syntax:application(F1, Vs)),
+            C1 = clone(E1, erl_syntax:clause([], [E1])),
+            E2 = clone(C1, erl_syntax:fun_expr([C1])),
+            C2 = clone(E2, erl_syntax:clause(Vs, [], [E2])),
+            E3 = clone(C2, erl_syntax:fun_expr([C2])),
+            E4 = clone(E3, erl_syntax:application(E3, As1)),
+            E5 = erl_syntax_lib:annotate_bindings(E4, get_env(A1)),
+            {E6, St2} = visit(E5, Env, St1),
+            F2 = rewrite(F, erl_syntax:atom(N)),
+            visit_nonlocal_application(F2, Ps ++ [E6], Tree, Env, St2);
+        false ->
+            visit_application_final(F, Ps ++ As, Tree, St0)
+    end;
+visit_spawn_call(_, F, Ps, As, Tree, _Env, St0) ->
+    visit_application_final(F, Ps ++ As, Tree, St0).
+
+visit_named_fun_application(F, As, Tree, Env, St0) ->
+    Name = erl_syntax:implicit_fun_name(F),
+    case catch {ok, erl_syntax_lib:analyze_function_name(Name)} of
+        {ok, {A, N}} when is_atom(A), is_integer(N), N =:= length(As) ->
+            case is_nonlocal({A, N}, Env) of
+                true ->
+                    %% Making this a direct call would be an error.
+                    visit_application_final(F, As, Tree, St0);
+                false ->
+                    report({Env#env.file, erl_syntax:get_pos(F),
+			    "changing application of implicit fun "
+			    "to direct local call."},
+			   [], Env#env.verbosity),
+                    Used = sets:add_element({A, N}, St0#st.used),
+                    F1 = rewrite(F, erl_syntax:atom(A)),
+                    revisit_application(F1, As, Tree, Env,
+                                        St0#st{used = Used})
+            end;
+        _  ->
+            visit_application_final(F, As, Tree, St0)
+    end.
+
+visit_lambda_application(F, As, Tree, Env, St0) ->
+    A = erl_syntax:fun_expr_arity(F),
+    case A =:= length(As) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "changing application of fun-expression "
+		    "to local function call."},
+		   [], Env#env.verbosity),
+            {Base, _} = Env#env.current,
+            Free = [erl_syntax:variable(V) || V <- get_free_vars(F)],
+            N = length(Free),
+            A1 = A + N,
+            {Name, St1} = new_fname({Base, A1}, St0),
+            Cs = augment_clauses(erl_syntax:fun_expr_clauses(F), Free),
+            F1 = erl_syntax:atom(Name),
+            New = rewrite(F, erl_syntax:function(F1, Cs)),
+            Used = sets:add_element({Name, A1}, St1#st.used),
+            Forms = [New | St1#st.new_forms],
+            St2 = St1#st{new_forms = Forms, used = Used},
+            visit_application_final(F1, As ++ Free, Tree, St2);
+        false ->
+            warn({Env#env.file, erl_syntax:get_pos(F),
+		  "arity mismatch in fun-expression application."},
+		 [], Env#env.verbosity),
+            visit_application_final(F, As, Tree, St0)
+    end.
+
+augment_clauses(Cs, Vs) ->
+    [begin
+	 Ps = erl_syntax:clause_patterns(C),
+	 G = erl_syntax:clause_guard(C),
+	 Es = erl_syntax:clause_body(C),
+	 rewrite(C, erl_syntax:clause(Ps ++ Vs, G, Es))
+     end
+     || C <- Cs].
+
+visit_nonlocal_application(F, As, Tree, Env, St0) ->
+    case erl_syntax:type(F) of
+        tuple ->
+            case erl_syntax:tuple_elements(F) of
+                [X1, X2] ->
+                    report({Env#env.file, erl_syntax:get_pos(F),
+			    "changing application of 2-tuple "
+			    "to direct remote call."},
+			   [], Env#env.verbosity),
+                    F1 = erl_syntax:module_qualifier(X1, X2),
+                    revisit_application(rewrite(F, F1), As, Tree, Env,
+                                        St0);
+                _ ->
+                    visit_application_final(F, As, Tree, St0)
+            end;
+        module_qualifier ->
+            case catch {ok, erl_syntax_lib:analyze_function_name(F)} of
+                {ok, {M, N}} when is_atom(M), is_atom(N) ->
+                    visit_remote_application({M, N, length(As)}, F, As,
+                                             Tree, Env, St0);
+                _ ->
+                    visit_application_final(F, As, Tree, St0)
+            end;
+        _ ->
+            visit_application_final(F, As, Tree, St0)
+    end.
+
+%% --- lists:append/2 and lists:subtract/2 ---
+visit_remote_application({lists, append, 2}, F, [A1, A2], Tree, Env,
+                         St0) ->
+    report({Env#env.file, erl_syntax:get_pos(F),
+	    "replacing call to `lists:append/2' "
+	    "with the `++' operator."},
+	   [], Env#env.verbosity),
+    Tree1 = erl_syntax:infix_expr(A1, erl_syntax:operator('++'), A2),
+    visit(rewrite(Tree, Tree1), Env, St0);
+visit_remote_application({lists, subtract, 2}, F, [A1, A2], Tree, Env,
+                         St0) ->
+    report({Env#env.file, erl_syntax:get_pos(F),
+	    "replacing call to `lists:subtract/2' "
+	    "with the `--' operator."},
+	   [], Env#env.verbosity),
+    Tree1 = erl_syntax:infix_expr(A1, erl_syntax:operator('--'), A2),
+    visit(rewrite(Tree, Tree1), Env, St0);
+%% --- lists:map/2 and lists:filter/2 ---
+visit_remote_application({lists, filter, 2}, F, [A1, A2] = As, Tree,
+                         Env, St0) ->
+    case Env#env.auto_list_comp
+	and (erl_syntax:type(A1) =/= variable)
+	and (get_var_exports(A1) =:= [])
+	and (get_var_exports(A2) =:= []) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "replacing call to `lists:filter/2' "
+		    "with a list comprehension."},
+		   [], Env#env.verbosity),
+            {V, St1} = new_variable(St0),
+            G = clone(A2, erl_syntax:generator(V, A2)),
+            T = clone(A1, erl_syntax:application(A1, [V])),
+            L = erl_syntax:list_comp(V, [G, T]),
+            L1 = erl_syntax_lib:annotate_bindings(L, get_env(Tree)),
+            visit(rewrite(Tree, L1), Env, St1);
+        false ->
+            visit_application_final(F, As, Tree, St0)
+    end;
+visit_remote_application({lists, map, 2}, F, [A1, A2] = As, Tree, Env,
+                         St0) ->
+    case Env#env.auto_list_comp
+	and (erl_syntax:type(A1) =/= variable)
+	and (get_var_exports(A1) =:= [])
+	and (get_var_exports(A2) =:= []) of
+        true ->
+            report({Env#env.file, erl_syntax:get_pos(F),
+		    "replacing call to `lists:map/2' "
+		    "with a list comprehension."},
+		   [], Env#env.verbosity),
+            {V, St1} = new_variable(St0),
+            T = clone(A1, erl_syntax:application(A1, [V])),
+            G = clone(A2, erl_syntax:generator(V, A2)),
+            L = erl_syntax:list_comp(T, [G]),
+            L1 = erl_syntax_lib:annotate_bindings(L, get_env(Tree)),
+            visit(rewrite(Tree, L1), Env, St1);
+        false ->
+            visit_application_final(F, As, Tree, St0)
+    end;
+%% --- all other functions ---
+visit_remote_application({M, N, A} = Name, F, As, Tree, Env, St) ->
+    case is_auto_imported(Name) of
+        true ->
+            %% We don't remove the qualifier - it might be there for the
+            %% sake of clarity.
+            visit_bif_call({N, A}, F, As, Tree, Env, St);
+        false ->
+            case rename_remote_call(Name, St) of
+                {M1, N1} ->
+                    report({Env#env.file, erl_syntax:get_pos(F),
+			    "updating obsolete call to `~w:~w/~w' "
+			    "to use `~w:~w/~w' instead."},
+			   [M, N, A, M1, N1, A], Env#env.verbosity),
+                    M2 = erl_syntax:atom(M1),
+                    N2 = erl_syntax:atom(N1),
+                    F1 = erl_syntax:module_qualifier(M2, N2),
+                    revisit_application(rewrite(F, F1), As, Tree, Env,
+                                        St);
+                false ->
+                    visit_application_final(F, As, Tree, St)
+            end
+    end.
+
+-spec auto_expand_import(mfa(), #st{}) -> boolean().
+
+auto_expand_import({lists, append, 2}, _St) -> true;
+auto_expand_import({lists, subtract, 2}, _St) -> true;
+auto_expand_import({lists, filter, 2}, _St) -> true;
+auto_expand_import({lists, map, 2}, _St) -> true;
+auto_expand_import(Name, St) ->
+    case is_auto_imported(Name) of
+        true ->
+            true;
+        false ->
+            rename_remote_call(Name, St) =/= false
+    end.
+
+visit_list_comp(Tree, Env, St0) ->
+    Es = erl_syntax:list_comp_body(Tree),
+    {Es1, St1} = visit_list_comp_body(Es, Env, St0),
+    {T, St2} = visit(erl_syntax:list_comp_template(Tree), Env, St1),
+    {rewrite(Tree, erl_syntax:list_comp(T, Es1)), St2}.
+
+visit_list_comp_body_join(Env) ->
+    fun (E, St0) ->
+            case is_generator(E) of
+                true ->
+                    visit_generator(E, Env, St0);
+                false ->
+                    visit_filter(E, Env, St0)
+            end
+    end.
+
+visit_list_comp_body(Es, Env, St0) ->
+    lists:mapfoldl(visit_list_comp_body_join(Env), St0, Es).
+
+%% 'visit_filter' also handles uninteresting generators.
+
+visit_filter(E, Env, St0) ->
+    visit(E, Env, St0).
+
+%% "interesting" generators have the form V <- [V || ...]; this can be
+%% unfolded as long as no bindings become erroneously shadowed.
+
+visit_generator(G, Env, St0) ->
+    P = erl_syntax:generator_pattern(G),
+    case erl_syntax:type(P) of
+        variable ->
+            B = erl_syntax:generator_body(G),
+            case erl_syntax:type(B) of
+                list_comp ->
+                    T = erl_syntax:list_comp_template(B),
+                    case erl_syntax:type(T) of
+                        variable ->
+                            visit_generator_1(G, Env, St0);
+                        _ ->
+                            visit_filter(G, Env, St0)
+                    end;
+                _ ->
+                    visit_filter(G, Env, St0)
+            end;
+        _ ->
+            visit_filter(G, Env, St0)
+    end.
+
+visit_generator_1(G, Env, St0) ->
+    recommend({Env#env.file, erl_syntax:get_pos(G),
+	       "unfold that this nested list comprehension can be unfolded "
+	       "by hand to get better efficiency."},
+	      [], Env#env.verbosity),
+    visit_filter(G, Env, St0).
+
+visit_match_expr(Tree, Env, St0) ->
+    %% We do not visit the pattern (for now, anyway).
+    P = erl_syntax:match_expr_pattern(Tree),
+    {B, St1} = visit(erl_syntax:match_expr_body(Tree), Env, St0),
+    case erl_syntax:type(P) of
+        tuple ->
+            Ps = erl_syntax:tuple_elements(P),
+            case lists:all(fun is_variable/1, Ps) of
+                true ->
+                    Vs = lists:sort([erl_syntax:variable_name(X)
+                                     || X <- Ps]),
+                    case ordsets:is_set(Vs) of
+                        true ->
+                            Xs = get_var_exports(B),
+                            case ordsets:intersection(Vs, Xs) of
+                                [] ->
+                                    visit_match_body(Ps, P, B, Tree,
+                                                     Env, St1);
+                                _ ->
+                                    visit_match_expr_final(P, B, Tree,
+                                                           Env, St1)
+                            end;
+                        false ->
+                            visit_match_expr_final(P, B, Tree, Env, St1)
+                    end;
+                false ->
+                    visit_match_expr_final(P, B, Tree, Env, St1)
+            end;
+        _  ->
+            visit_match_expr_final(P, B, Tree, Env, St1)
+    end.
+
+visit_match_expr_final(P, B, Tree, _Env, St0) ->
+    {rewrite(Tree, erl_syntax:match_expr(P, B)), St0}.
+
+visit_match_body(_Ps, P, B, Tree, #env{auto_export_vars = false} = Env,
+                 St0) ->
+    visit_match_expr_final(P, B, Tree, Env, St0);
+visit_match_body(Ps, P, B, Tree, Env, St0) ->
+    case erl_syntax:type(B) of
+        case_expr ->
+            Cs = erl_syntax:case_expr_clauses(B),
+            case multival_clauses(Cs, length(Ps), Ps) of
+                {true, Cs1} ->
+                    report_export_vars(Env#env.file,
+				       erl_syntax:get_pos(B),
+				       "case", Env#env.verbosity),
+                    A = erl_syntax:case_expr_argument(B),
+                    Tree1 = erl_syntax:case_expr(A, Cs1),
+                    {rewrite(Tree, Tree1), St0};
+                false ->
+                    visit_match_expr_final(P, B, Tree, Env, St0)
+            end;
+        if_expr ->
+            Cs = erl_syntax:if_expr_clauses(B),
+            case multival_clauses(Cs, length(Ps), Ps) of
+                {true, Cs1} ->
+                    report_export_vars(Env#env.file,
+				       erl_syntax:get_pos(B),
+				       "if", Env#env.verbosity),
+                    Tree1 = erl_syntax:if_expr(Cs1),
+                    {rewrite(Tree, Tree1), St0};
+                false ->
+                    visit_match_expr_final(P, B, Tree, Env, St0)
+            end;
+        cond_expr ->
+            Cs = erl_syntax:cond_expr_clauses(B),
+            case multival_clauses(Cs, length(Ps), Ps) of
+                {true, Cs1} ->
+                    report_export_vars(Env#env.file,
+				       erl_syntax:get_pos(B),
+				       "cond", Env#env.verbosity),
+                    Tree1 = erl_syntax:cond_expr(Cs1),
+                    {rewrite(Tree, Tree1), St0};
+                false ->
+                    visit_match_expr_final(P, B, Tree, Env, St0)
+            end;
+        receive_expr ->
+            %% Handle the timeout case as an extra clause.
+            As = erl_syntax:receive_expr_action(B),
+            C = erl_syntax:clause([], As),
+            Cs = erl_syntax:receive_expr_clauses(B),
+            case multival_clauses([C | Cs], length(Ps), Ps) of
+                {true, [C1 | Cs1]} ->
+                    report_export_vars(Env#env.file,
+				       erl_syntax:get_pos(B),
+				       "receive", Env#env.verbosity),
+                    T = erl_syntax:receive_expr_timeout(B),
+                    As1 = erl_syntax:clause_body(C1),
+                    Tree1 = erl_syntax:receive_expr(Cs1, T, As1),
+                    {rewrite(Tree, Tree1), St0};
+                false ->
+                    visit_match_expr_final(P, B, Tree, Env, St0)
+            end;
+        _ ->
+            visit_match_expr_final(P, B, Tree, Env, St0)
+    end.
+
+multival_clauses(Cs, N, Vs) ->
+    multival_clauses(Cs, N, Vs, []).
+
+multival_clauses([C | Cs], N, Vs, Cs1) ->
+    case erl_syntax:clause_body(C) of
+        [] ->
+            false;
+        Es ->
+            E = lists:last(Es),
+            case erl_syntax:type(E) of
+                tuple ->
+                    Ts = erl_syntax:tuple_elements(E),
+                    if length(Ts) =:= N ->
+                            Bs = make_matches(E, Vs, Ts),
+                            Es1 = replace_last(Es, Bs),
+                            Ps = erl_syntax:clause_patterns(C),
+                            G = erl_syntax:clause_guard(C),
+                            C1 = erl_syntax:clause(Ps, G, Es1),
+                            multival_clauses(Cs, N, Vs,
+                                             [rewrite(C, C1) | Cs1]);
+                       true ->
+                            false
+                    end;
+                _ ->
+                    case erl_syntax_lib:is_fail_expr(E) of
+                        true ->
+                            %% We must add dummy bindings here so we
+                            %% don't introduce compilation errors due to
+                            %% "unsafe" variable exports.
+                            Bs = make_matches(Vs,
+                                              erl_syntax:atom(false)),
+                            Es1 = replace_last(Es, Bs ++ [E]),
+                            Ps = erl_syntax:clause_patterns(C),
+                            G = erl_syntax:clause_guard(C),
+                            C1 = erl_syntax:clause(Ps, G, Es1),
+                            multival_clauses(Cs, N, Vs,
+                                             [rewrite(C, C1) | Cs1]);
+                        false ->
+                            false
+                    end
+            end
+    end;
+multival_clauses([], _N, _Vs, Cs) ->
+    {true, lists:reverse(Cs)}.
+
+make_matches(E, Vs, Ts) ->
+    case make_matches(Vs, Ts) of
+        [] ->
+            [];
+        [B | Bs] ->
+            [rewrite(E, B) | Bs]    % preserve comments on E (but not B)
+    end.
+
+make_matches([V | Vs], [T | Ts]) ->
+    [erl_syntax:match_expr(V, T) | make_matches(Vs, Ts)];
+make_matches([V | Vs], T) when T =/= [] ->
+    [erl_syntax:match_expr(V, T) | make_matches(Vs, T)];
+make_matches([], _) ->
+    [].
+
+rename_remote_call(F, St) ->
+    case dict:find(F, St#st.rename) of
+        error ->
+            rename_remote_call_1(F);
+        {ok, F1} -> F1
+    end.
+
+-spec rename_remote_call_1(mfa()) -> {atom(), atom()} | 'false'.
+rename_remote_call_1({dict, dict_to_list, 1}) -> {dict, to_list};
+rename_remote_call_1({dict, list_to_dict, 1}) -> {dict, from_list};
+rename_remote_call_1({erl_eval, arg_list, 2}) -> {erl_eval, expr_list};
+rename_remote_call_1({erl_eval, arg_list, 3}) -> {erl_eval, expr_list};
+rename_remote_call_1({erl_eval, seq, 2}) -> {erl_eval, exprs};
+rename_remote_call_1({erl_eval, seq, 3}) -> {erl_eval, exprs};
+rename_remote_call_1({erl_pp, seq, 1}) -> {erl_eval, seq};
+rename_remote_call_1({erl_pp, seq, 2}) -> {erl_eval, seq};
+rename_remote_call_1({erlang, info, 1}) -> {erlang, system_info};
+rename_remote_call_1({io, parse_erl_seq, 1}) -> {io, parse_erl_exprs};
+rename_remote_call_1({io, parse_erl_seq, 2}) -> {io, parse_erl_exprs};
+rename_remote_call_1({io, parse_erl_seq, 3}) -> {io, parse_erl_exprs};
+rename_remote_call_1({io, scan_erl_seq, 1}) -> {io, scan_erl_exprs};
+rename_remote_call_1({io, scan_erl_seq, 2}) -> {io, scan_erl_exprs};
+rename_remote_call_1({io, scan_erl_seq, 3}) -> {io, scan_erl_exprs};
+rename_remote_call_1({io_lib, reserved_word, 1}) -> {erl_scan, reserved_word};
+rename_remote_call_1({io_lib, scan, 1}) -> {erl_scan, string};
+rename_remote_call_1({io_lib, scan, 2}) -> {erl_scan, string};
+rename_remote_call_1({io_lib, scan, 3}) -> {erl_scan, tokens};
+rename_remote_call_1({orddict, dict_to_list, 1}) -> {orddict, to_list};
+rename_remote_call_1({orddict, list_to_dict, 1}) -> {orddict, from_list};
+rename_remote_call_1({ordsets, list_to_set, 1}) -> {ordsets, from_list};
+rename_remote_call_1({ordsets, new_set, 0}) -> {ordsets, new};
+rename_remote_call_1({ordsets, set_to_list, 1}) -> {ordsets, to_list};
+rename_remote_call_1({ordsets, subset, 2}) -> {ordsets, is_subset};
+rename_remote_call_1({sets, list_to_set, 1}) -> {sets, from_list};
+rename_remote_call_1({sets, new_set, 0}) -> {sets, new};
+rename_remote_call_1({sets, set_to_list, 1}) -> {sets, to_list};
+rename_remote_call_1({sets, subset, 2}) -> {sets, is_subset};
+rename_remote_call_1({string, index, 2}) -> {string, str};
+rename_remote_call_1({unix, cmd, 1}) -> {os, cmd};
+rename_remote_call_1(_) -> false.
+
+-spec rewrite_guard_test(atom(), byte()) -> atom().
+rewrite_guard_test(atom, 1) -> is_atom;
+rewrite_guard_test(binary, 1) -> is_binary;
+rewrite_guard_test(constant, 1) -> is_constant;
+rewrite_guard_test(float, 1) -> is_float;
+rewrite_guard_test(function, 1) -> is_function;
+rewrite_guard_test(function, 2) -> is_function;
+rewrite_guard_test(integer, 1) -> is_integer;
+rewrite_guard_test(list, 1) -> is_list;
+rewrite_guard_test(number, 1) -> is_number;
+rewrite_guard_test(pid, 1) -> is_pid;
+rewrite_guard_test(port, 1) -> is_port;
+rewrite_guard_test(reference, 1) -> is_reference;
+rewrite_guard_test(tuple, 1) -> is_tuple;
+rewrite_guard_test(record, 2) -> is_record;
+rewrite_guard_test(record, 3) -> is_record;
+rewrite_guard_test(N, _A) -> N.
+
+-spec reverse_guard_test(atom(), byte()) -> atom().
+reverse_guard_test(is_atom, 1) -> atom;
+reverse_guard_test(is_binary, 1) -> binary;
+reverse_guard_test(is_constant, 1) -> constant;
+reverse_guard_test(is_float, 1) -> float;
+reverse_guard_test(is_function, 1) -> function;
+reverse_guard_test(is_function, 2) -> function;
+reverse_guard_test(is_integer, 1) -> integer;
+reverse_guard_test(is_list, 1) -> list;
+reverse_guard_test(is_number, 1) -> number;
+reverse_guard_test(is_pid, 1) -> pid;
+reverse_guard_test(is_port, 1) -> port;
+reverse_guard_test(is_reference, 1) -> reference;
+reverse_guard_test(is_tuple, 1) -> tuple;
+reverse_guard_test(is_record, 2) -> record;
+reverse_guard_test(is_record, 3) -> record;
+reverse_guard_test(N, _A) -> N.
+
+
+%% =====================================================================
+%% Utility functions
+
+is_remote_name({M,F,A}) when is_atom(M), is_atom(F), is_integer(A) -> true;
+is_remote_name(_) -> false.
+
+is_atom_pair({M,F}) when is_atom(M), is_atom(F) -> true;
+is_atom_pair(_) -> false.
+
+replace_last([_E], Xs) ->
+    Xs;
+replace_last([E | Es], Xs) ->
+    [E | replace_last(Es, Xs)].
+
+is_generator(E) ->
+    erl_syntax:type(E) =:= generator.
+
+is_variable(E) ->
+    erl_syntax:type(E) =:= variable.
+
+new_variables(N, St0) when N > 0 ->
+    {V, St1} = new_variable(St0),
+    {Vs, St2} = new_variables(N - 1, St1),
+    {[V | Vs], St2};
+new_variables(0, St) ->
+    {[], St}.
+
+new_variable(St0) ->
+    Fun = fun (N) ->
+                  list_to_atom("V" ++ integer_to_list(N))
+          end,
+    Vs = St0#st.vars,
+    {Name, N} = new_name(St0#st.varc, Fun, Vs),
+    St1 = St0#st{varc = N + 1, vars = sets:add_element(Name, Vs)},
+    {erl_syntax:variable(Name), St1}.
+
+new_fname({F, A}, St0) ->
+    Base = atom_to_list(F),
+    Fun = fun (N) ->
+                  {list_to_atom(Base ++ "_" ++ integer_to_list(N)), A}
+          end,
+    Fs = St0#st.functions,
+    {{F1, _A} = Name, _N} = new_name(1, Fun, Fs),
+    {F1, St0#st{functions = sets:add_element(Name, Fs)}}.
+
+new_name(N, F, Set) ->
+    Name = F(N),
+    case sets:is_element(Name, Set) of
+        true ->
+            new_name(N + 1, F, Set);
+        false ->
+            {Name, N}
+    end.
+
+is_imported(F, Env) ->
+    dict:is_key(F, Env#env.imports).
+
+is_auto_imported({erlang, N, A}) ->
+    is_auto_imported({N, A});
+is_auto_imported({_, _N, _A}) ->
+    false;
+is_auto_imported({N, A}) ->
+    erl_internal:bif(N, A).
+
+is_nonlocal(N, Env) ->
+    case is_imported(N, Env) of
+        true ->
+            true;
+        false ->
+            is_auto_imported(N)
+    end.
+
+get_var_exports(Node) ->
+    get_var_exports_1(erl_syntax:get_ann(Node)).
+
+get_var_exports_1([{bound, B} | _Bs]) -> B;
+get_var_exports_1([_ | Bs]) -> get_var_exports_1(Bs);
+get_var_exports_1([]) -> [].
+
+get_free_vars(Node) ->
+    get_free_vars_1(erl_syntax:get_ann(Node)).
+
+get_free_vars_1([{free, B} | _Bs]) -> B;
+get_free_vars_1([_ | Bs]) -> get_free_vars_1(Bs);
+get_free_vars_1([]) -> [].
+
+filename([C | T]) when is_integer(C), C > 0, C =< 255 ->
+    [C | filename(T)];
+filename([H|T]) ->
+    filename(H) ++ filename(T);
+filename([]) ->
+    [];
+filename(N) when is_atom(N) ->
+    atom_to_list(N);
+filename(N) ->
+    report_error("bad filename: `~P'.", [N, 25]),
+    exit(error).
+
+get_env(Tree) ->
+    case lists:keyfind(env, 1, erl_syntax:get_ann(Tree)) of
+        {env, Env} ->
+            Env;
+        _ ->
+            []
+    end.
+
+rewrite(Source, Target) ->
+    erl_syntax:copy_attrs(Source, Target).
+
+clone(Source, Target) ->
+    erl_syntax:copy_pos(Source, Target).
+
+
+%% =====================================================================
+%% Reporting
+
+report_export_vars(F, L, Type, Opts) ->
+    report({F, L, "rewrote ~s-expression to export variables."},
+	   [Type], Opts).
+
+error_read_file(Name) ->
+    report_error("error reading file `~s'.", [filename(Name)]).
+
+error_write_file(Name) ->
+    report_error("error writing to file `~s'.", [filename(Name)]).
+
+error_backup_file(Name) ->
+    report_error("could not create backup of file `~s'.",
+                 [filename(Name)]).
+
+error_open_output(Name) ->
+    report_error("cannot open file `~s' for output.", [filename(Name)]).
+
+verbosity(Opts) ->
+    case proplists:get_bool(quiet, Opts) of 
+        true -> 0;
+        false ->
+            case proplists:get_value(verbose, Opts) of
+                true -> 2;
+                N when is_integer(N) -> N; 
+                _ -> 1
+            end
+    end.
+
+report_error(D) ->
+    report_error(D, []).
+    
+report_error({F, L, D}, Vs) ->
+    report({F, L, {error, D}}, Vs);
+report_error(D, Vs) ->
+    report({error, D}, Vs).
+
+%% warn(D, N) ->
+%%     warn(D, [], N).
+
+warn({F, L, D}, Vs, N) ->
+    report({F, L, {warning, D}}, Vs, N);
+warn(D, Vs, N) ->
+    report({warning, D}, Vs, N).
+
+recommend(D, Vs, N) ->
+    report({recommend, D}, Vs, N).
+
+verbose(D, Vs, N) ->
+    report(2, D, Vs, N).
+
+report(D, Vs) ->
+    report(D, Vs, 1).
+
+report(D, Vs, N) ->
+    report(1, D, Vs, N).
+
+report(Level, _D, _Vs, N) when is_integer(N), N < Level ->
+    ok;
+report(_Level, D, Vs, N) when is_integer(N) ->
+    io:put_chars(format(D, Vs));
+report(Level, D, Vs, Options) when is_list(Options) ->
+    report(Level, D, Vs, verbosity(Options)).
+
+format({error, D}, Vs) ->
+    ["error: ", format(D, Vs)];
+format({warning, D}, Vs) ->
+    ["warning: ", format(D, Vs)];
+format({recommend, D}, Vs) ->
+    ["recommendation: ", format(D, Vs)];
+format({"", L, D}, Vs) when is_integer(L), L > 0 ->
+    [io_lib:fwrite("~w: ", [L]), format(D, Vs)];
+format({"", _L, D}, Vs) ->
+    format(D, Vs);
+format({F, L, D}, Vs) when is_integer(L), L > 0 ->
+    [io_lib:fwrite("~s:~w: ", [filename(F), L]), format(D, Vs)];
+format({F, _L, D}, Vs) ->
+    [io_lib:fwrite("~s: ", [filename(F)]), format(D, Vs)];
+format(S, Vs) when is_list(S) ->
+    [io_lib:fwrite(S, Vs), $\n].
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/igor.erl b/lib/syntax_tools/src/igor.erl
new file mode 100644
index 0000000000..9e7b784170
--- /dev/null
+++ b/lib/syntax_tools/src/igor.erl
@@ -0,0 +1,3023 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 1998-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc Igor: the Module Merger and Renamer.
+%%
+%% The program Igor merges the source code of one or more Erlang
+%% modules into a single module, which can then replace the original set
+%% of modules. Igor is also able to rename a set of (possibly
+%% interdependent) modules, without joining them into a single
+%% module.
+%%
+%% The main user interface consists of the functions {@link merge/3} and
+%% {@link rename/3}. See also the function {@link parse_transform/2}.
+%%
+%% A note of warning: Igor cannot do anything about the case when the
+%% name of a remote function is passed to the built-in functions
+%% `apply' and `spawn' <em>unless</em> the module
+%% and function names are explicitly stated in the call, as in e.g.
+%% `apply(lists, reverse, [Xs])'. In all other cases, Igor
+%% leaves such calls unchanged, and warns the user that manual editing
+%% might be necessary.
+%%
+%% Also note that Erlang records will be renamed as necessary to
+%% avoid non-equivalent definitions using the same record name. This
+%% does not work if the source code accesses the name field of such
+%% record tuples by `element/2' or similar methods. Always
+%% use the record syntax to handle record tuples, if possible.
+%%
+%% Disclaimer: the author of this program takes no responsibility for
+%% the correctness of the produced output, or for any effects of its
+%% execution. In particular, the author may not be held responsible
+%% should Igor include the code of a deceased madman in the result.
+%%
+%% For further information on Igors in general, see e.g. "Young
+%% Frankenstein", Mel Brooks, 1974, and "The Fifth Elephant", Terry
+%% Pratchett, 1999.
+%% @end
+%% =====================================================================
+
+
+%% This program is named after the character Igor, assistant to Dr.
+%% Frankenstein, in the 1939 film "Son of Frankenstein" (with Boris
+%% Karloff playing The Monster for the last time; Igor was played by
+%% Bela Lugosi). Igor's job (in the film) was mainly to bring reasonably
+%% fresh parts of various human corpses to the good Doctor, for his
+%% purpose of reanimating them in the shape of a new formidable, living
+%% creature.
+%%
+%% Merging code is done by joining the sources, possibly changing the
+%% order of declarations as necessary, renaming functions and records to
+%% avoid name clashes, and changing remote calls to local calls where
+%% possible. Stub modules may be automatically generated to redirect any
+%% calls that still use the old names. Indirectly, code merging can be
+%% used to simply rename a set of modules.
+%%
+%% What Igor does not do is to optimise the resulting code, which
+%% typically can benefit from techniques such as inlining, constant
+%% folding, specialisation, etc. This task is left to the Doctor.
+%% (Luckily, Igor can call on Inga to do some cleanup; cf. 'erl_tidy'.)
+
+%% TODO: FIXME: don't remove module qualifier if name is (auto-)imported!
+%% TODO: handle merging of parameterized modules (somehow).
+%% TODO: check for redefinition of macros; check equivalence; comment out.
+%% TODO: {export, [E]}, E = atom() | {atom(), atom(), integer()}.
+%% TODO: improve documentation. 
+%% TODO: optionally rename all functions from specified (or all) modules.
+
+-module(igor).
+
+-export([create_stubs/2, merge/2, merge/3, merge_files/3, merge_files/4,
+	 merge_sources/3, parse_transform/2, rename/2, rename/3]).
+
+-include_lib("kernel/include/file.hrl").
+
+
+%% =====================================================================
+%% Global Constants
+
+-define(NOTE_HEADER, "Note from Igor: ").
+-define(COMMENT_PREFIX, "% ").
+-define(COMMENT_BAR,
+	"======================="
+	"======================="
+	"=======================").
+-define(NOTE_PREFIX, "%! ").
+-define(KILL_PREFIX, "%<<< ").
+-define(DEFAULT_INCLUDES, ["."]).
+-define(DEFAULT_MACROS, []).
+-define(DEFAULT_SUFFIX, ".erl").
+-define(DEFAULT_BACKUP_SUFFIX, ".bak").
+-define(DEFAULT_DIR, "").
+-define(DEFAULT_STUB_DIR, "stubs").
+-define(TIDY_OPTS, [quiet]).
+
+%% This may also be used in patterns. R must not be an integer, i.e.,
+%% the structure must be distinct from function names.
+
+-define(record_name(R), {record, R}).
+
+
+%% Data structure for module information
+
+-record(module, {name,		% = atom()
+		 vars = none,	% = [atom()] | none
+		 functions,	% = ordset({atom(), int()})
+		 exports,	% = ordset({atom(), int()})
+				% | ordset({{atom(), int()},
+				%	    term()})
+		 aliases,	% = ordset({{atom(), int()},
+				%	    {atom(),
+				%	     {atom(), int()}}})
+		 attributes,	% = ordset({atom(), term()})
+		 records	% = [{atom(), [{atom(), term()}]}]
+		}).
+
+%% The default pretty-printing function.
+
+default_printer(Tree, Options) ->
+    erl_prettypr:format(Tree, Options).
+
+
+%% =====================================================================
+%% @spec parse_transform(Forms::[syntaxTree()], Options::[term()]) ->
+%%           [syntaxTree()]
+%%
+%%         syntaxTree() = erl_syntax:syntaxTree()
+%%
+%% @doc Allows Igor to work as a component of the Erlang compiler.
+%% Including the term `{parse_transform, igor}' in the
+%% compile options when compiling an Erlang module (cf.
+%% `compile:file/2'), will call upon Igor to process the
+%% source code, allowing automatic inclusion of other source files. No
+%% files are created or overwritten when this function is used.
+%%
+%% Igor will look for terms `{igor, List}' in the compile
+%% options, where `List' is a list of Igor-specific options,
+%% as follows:
+%% <dl>
+%%  <dt>`{files, [filename()]}'</dt>
+%%    <dd>The value specifies a list of source files to be merged with
+%%    the file being compiled; cf. `merge_files/4'.</dd>
+%% </dl>
+%%
+%% See `merge_files/4' for further options. Note, however,
+%% that some options are preset by this function and cannot be
+%% overridden by the user; in particular, all cosmetic features are
+%% turned off, for efficiency. Preprocessing is turned on.
+%%
+%% @see merge_files/4
+%% @see //compiler/compile:file/2
+
+parse_transform(Forms, Options) ->
+    M = get_module_info(Forms),
+    Name = M#module.name,
+    Opts = proplists:append_values(igor, Options),
+    Files = proplists:append_values(files, Opts),
+    %% We turn off all features that are only cosmetic, and make sure to
+    %% turn on preservation of `file' attributes.
+    Opts1 = [{comments, false},
+	     {notes, no},
+	     {no_imports, true},
+	     {file_attributes, yes},
+	     {preprocess, true},
+	     {export, [Name]}
+	     | Opts],
+    {T, _} = merge_files(Name, [Forms], Files, Opts1),
+    verbose("done.", Opts1),
+    erl_syntax:revert_forms(T).
+
+
+%% =====================================================================
+%% @spec merge(Name::atom(), Files::[filename()]) -> [filename()]
+%% @equiv merge(Name, Files, [])
+
+merge(Name, Files) ->
+    merge(Name, Files, []).
+
+%% =====================================================================
+%% @spec merge(Name::atom(), Files::[filename()], Options::[term()]) ->
+%%           [filename()]
+%%
+%%	    filename() = file:filename()
+%%
+%% @doc Merges source code files to a single file. `Name'
+%% specifies the name of the resulting module - not the name of the
+%% output file. `Files' is a list of file names and/or module
+%% names of source modules to be read and merged (see
+%% `merge_files/4' for details). All the input modules must
+%% be distinctly named.
+%%
+%% The resulting source code is written to a file named
+%% "`<em>Name</em>.erl'" in the current directory, unless
+%% otherwise specified by the options `dir' and
+%% `outfile' described below.
+%%
+%% Examples:
+%% <ul>
+%%   <li>given a module `m' in file "`m.erl'"
+%%   which uses the standard library module `lists', calling
+%%   `igor:merge(m, [m, lists])' will create a new file
+%%   "`m.erl' which contains the code from `m' and
+%%   exports the same functions, and which includes the referenced code
+%%   from the `lists' module. The original file will be
+%%   renamed to "`m.erl.bak'".</li>
+%%
+%%   <li>given modules `m1' and `m2', in
+%%   corresponding files, calling `igor:merge(m, [m1, m2])'
+%%   will create a file "`m.erl'" which contains the code
+%%   from `m1' and `m2' and exports the functions
+%%   of `m1'.</li>
+%% </ul>
+%%
+%% Stub module files are created for those modules that are to be
+%% exported by the target module (see options `export',
+%% `stubs' and `stub_dir').
+%%
+%% The function returns the list of file names of all created
+%% modules, including any automatically created stub modules. The file
+%% name of the target module is always first in the list.
+%%
+%% Note: If you get a "syntax error" message when trying to merge
+%% files (and you know those files to be correct), then try the
+%% `preprocess' option. It typically means that your code
+%% contains too strange macros to be handled without actually performing
+%% the preprocessor expansions.
+%% 
+%% Options:
+%% <dl>
+%%   <dt>`{backup_suffix, string()}'</dt>
+%%
+%%     <dd>Specifies the file name suffix to be used when a backup file
+%%     is created; the default value is `".bak"'.</dd>
+%%
+%%   <dt>`{backups, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', existing files will be
+%%     renamed before new files are opened for writing. The new names
+%%     are formed by appending the string given by the
+%%     `backup_suffix' option to the original name. The
+%%     default value is `true'.</dd>
+%%
+%%   <dt>`{dir, filename()}'</dt>
+%%
+%%     <dd>Specifies the name of the directory in which the output file
+%%     is to be written. An empty string is interpreted as the current
+%%     directory. By default, the current directory is used.</dd>
+%%
+%%   <dt>`{outfile, filename()}'</dt>
+%%
+%%     <dd>Specifies the name of the file (without suffix) to which the
+%%     resulting source code is to be written. By default, this is the
+%%     same as the `Name' argument.</dd>
+%%
+%%   <dt>`{preprocess, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', preprocessing will be done
+%%     when reading the source code. See `merge_files/4' for
+%%     details.</dd>
+%%
+%%   <dt>`{printer, Function}'</dt>
+%%     <dd><ul>
+%%       <li>`Function = (syntaxTree()) -> string()'</li>
+%%     </ul>
+%%     Specifies a function for prettyprinting Erlang syntax trees.
+%%     This is used for outputting the resulting module definition, as
+%%     well as for creating stub files. The function is assumed to
+%%     return formatted text for the given syntax tree, and should raise
+%%     an exception if an error occurs. The default formatting function
+%%     calls `erl_prettypr:format/2'.</dd>
+%%
+%%   <dt>`{stub_dir, filename()}'</dt>
+%%
+%%     <dd>Specifies the name of the directory to which any generated
+%%     stub module files are written. The default value is
+%%     `"stubs"'.</dd>
+%%
+%%   <dt>`{stubs, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', stub module files will be
+%%     automatically generated for all exported modules that do not have
+%%     the same name as the target module. The default value is
+%%     `true'.</dd>
+%%
+%%   <dt>`{suffix, string()}'</dt>
+%%
+%%     <dd>Specifies the suffix to be used for the output file names;
+%%     the default value is `".erl"'.</dd>
+%% </dl>
+%%
+%% See `merge_files/4' for further options.
+%%
+%% @see merge/2
+%% @see merge_files/4
+
+%% The defaults for 'merge' are also used for 'create_stubs'.
+
+-define(DEFAULT_MERGE_OPTS,
+	[{backup_suffix, ?DEFAULT_BACKUP_SUFFIX},
+	 backups, 
+	 {dir, ?DEFAULT_DIR},
+	 {printer, fun default_printer/2},
+	 {stub_dir, ?DEFAULT_STUB_DIR},
+	 stubs,
+	 {suffix, ?DEFAULT_SUFFIX},
+	 {verbose, false}]).
+
+merge(Name, Files, Opts) ->
+    Opts1 = Opts ++ ?DEFAULT_MERGE_OPTS,
+    {Tree, Stubs} = merge_files(Name, Files, Opts1),
+    Dir = proplists:get_value(dir, Opts1, ""),
+    Filename = proplists:get_value(outfile, Opts1, Name),
+    File = write_module(Tree, Filename, Dir, Opts1),
+    [File | maybe_create_stubs(Stubs, Opts1)].
+
+
+%% =====================================================================
+%% @spec merge_files(Name::atom(), Files::[filename()],
+%%                   Options::[term()]) ->
+%%           {syntaxTree(), [stubDescriptor()]}
+%% @equiv merge_files(Name, [], Files, Options)
+
+merge_files(Name, Files, Options) ->
+    merge_files(Name, [], Files, Options).
+
+
+%% =====================================================================
+%% @spec merge_files(Name::atom(), Sources::[Forms],
+%%                   Files::[filename()], Options::[term()]) ->
+%%           {syntaxTree(), [stubDescriptor()]}
+%%     Forms = syntaxTree() | [syntaxTree()]
+%%
+%% @doc Merges source code files and syntax trees to a single syntax
+%% tree. This is a file-reading front end to
+%% `merge_sources/3'. `Name' specifies the name of
+%% the resulting module - not the name of the output file.
+%% `Sources' is a list of syntax trees and/or lists of
+%% "source code form" syntax trees, each entry representing a module
+%% definition. `Files' is a list of file names and/or module
+%% names of source modules to be read and included. All the input
+%% modules must be distinctly named.
+%%
+%% If a name in `Files' is not the name of an existing
+%% file, Igor assumes it represents a module name, and tries to locate
+%% and read the corresponding source file. The parsed files are appended
+%% to `Sources' and passed on to
+%% `merge_sources/3', i.e., entries in `Sources'
+%% are listed before entries read from files.
+%%
+%% If no exports are listed by an `export' option (see
+%% `merge_sources/3' for details), then if `Name'
+%% is also the name of one of the input modules, that module will be
+%% exported; otherwise, the first listed module will be exported. Cf.
+%% the examples under `merge/3'.
+%%
+%% The result is a pair `{Tree, Stubs}', where
+%% `Tree' represents the source code that is the result of
+%% merging all the code in `Sources' and `Files',
+%% and `Stubs' is a list of stub module descriptors (see
+%% `merge_sources/3' for details).
+%%
+%% Options:
+%% <dl>
+%%   <dt>`{comments, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', source code comments in
+%%     the original files will be preserved in the output. The default
+%%     value is `true'.</dd>
+%%
+%%   <dt>`{find_src_rules, [{string(), string()}]}'</dt>
+%%
+%%     <dd>Specifies a list of rules for associating object files with
+%%     source files, to be passed to the function
+%%     `filename:find_src/2'. This can be used to change the
+%%     way Igor looks for source files. If this option is not specified,
+%%     the default system rules are used. The first occurrence of this
+%%     option completely overrides any later in the option list.</dd>
+%%
+%%   <dt>`{includes, [filename()]}'</dt>
+%%
+%%     <dd>Specifies a list of directory names for the Erlang
+%%     preprocessor, if used, to search for include files (cf. the
+%%     `preprocess' option). The default value is the empty
+%%     list. The directory of the source file and the current directory
+%%     are automatically appended to the list.</dd>
+%%
+%%   <dt>`{macros, [{atom(), term()}]}'</dt>
+%%
+%%     <dd>Specifies a list of "pre-defined" macro definitions for the
+%%     Erlang preprocessor, if used (cf. the `preprocess'
+%%     option). The default value is the empty list.</dd>
+%%
+%%   <dt>`{preprocess, bool()}'</dt>
+%%
+%%     <dd>If the value is `false', Igor will read source
+%%     files without passing them through the Erlang preprocessor
+%%     (`epp'), in order to avoid expansion of preprocessor
+%%     directives such as `-include(...).',
+%%     `-define(...).' and `-ifdef(...)', and
+%%     macro calls such as `?LINE' and `?MY_MACRO(x,
+%%     y)'. The default value is `false', i.e.,
+%%     preprocessing is not done. (See the module
+%%     `epp_dodger' for details.)
+%%
+%%     Notes: If a file contains too exotic definitions or uses of
+%%     macros, it will not be possible to read it without preprocessing.
+%%     Furthermore, Igor does not currently try to sort out multiple
+%%     inclusions of the same file, or redefinitions of the same macro
+%%     name. Therefore, when preprocessing is turned off, it may become
+%%     necessary to edit the resulting source code, removing such
+%%     re-inclusions and redefinitions.</dd>
+%% </dl>
+%%
+%% See `merge_sources/3' for further options.
+%%
+%% @see merge/3
+%% @see merge_files/3
+%% @see merge_sources/3
+%% @see //stdlib/filename:find_src/2
+%% @see epp_dodger
+
+merge_files(_, _Trees, [], _) ->
+    report_error("no files to merge."),
+    exit(badarg);
+merge_files(Name, Trees, Files, Opts) ->
+    Opts1 = Opts ++ [{includes, ?DEFAULT_INCLUDES},
+		     {macros, ?DEFAULT_MACROS},
+		     {preprocess, false},
+		     comments],
+    Sources = [read_module(F, Opts1) || F <- Files],
+    merge_sources(Name, Trees ++ Sources, Opts1).
+
+
+%% =====================================================================
+%% @spec merge_sources(Name::atom(), Sources::[Forms],
+%%                     Options::[term()]) ->
+%%           {syntaxTree(), [stubDescriptor()]}
+%%
+%%     Forms = syntaxTree() | [syntaxTree()]
+%%
+%% @type stubDescriptor() = [{ModuleName, Functions, [Attribute]}]
+%%	    ModuleName = atom()
+%%	    Functions = [{FunctionName, {ModuleName, FunctionName}}]
+%%	    FunctionName = {atom(), integer()}
+%%	    Attribute = {atom(), term()}.
+%%
+%%      A stub module descriptor contains the module name, a list of
+%%      exported functions, and a list of module attributes. Each
+%%      function is described by its name (which includes its arity),
+%%      and the corresponding module and function that it calls. (The
+%%      arities should always match.) The attributes are simply
+%%      described by key-value pairs.
+%%
+%% @doc Merges syntax trees to a single syntax tree. This is the main
+%% code merging "engine". `Name' specifies the name of the
+%% resulting module. `Sources' is a list of syntax trees of
+%% type `form_list' and/or lists of "source code form" syntax
+%% trees, each entry representing a module definition. All the input
+%% modules must be distinctly named.
+%%
+%% Unless otherwise specified by the options, all modules are assumed
+%% to be at least "static", and all except the target module are assumed
+%% to be "safe". See the `static' and `safe'
+%% options for details.
+%%
+%% If `Name' is also the name of one of the input modules,
+%% the code from that module will occur at the top of the resulting
+%% code, and no extra "header" comments will be added. In other words,
+%% the look of that module will be preserved.
+%%
+%% The result is a pair `{Tree, Stubs}', where
+%% `Tree' represents the source code that is the result of
+%% merging all the code in `Sources', and `Stubs'
+%% is a list of stub module descriptors (see below).
+%%
+%% `Stubs' contains one entry for each exported input
+%% module (cf. the `export' option), each entry describing a
+%% stub module that redirects calls of functions in the original module
+%% to the corresponding (possibly renamed) functions in the new module.
+%% The stub descriptors can be used to automatically generate stub
+%% modules; see `create_stubs/2'.
+%%
+%% Options:
+%% <dl>
+%%   <dt>`{export, [atom()]}'</dt>
+%%
+%%     <dd>Specifies a list of names of input modules whose interfaces
+%%     should be exported by the output module. A stub descriptor is
+%%     generated for each specified module, unless its name is
+%%     `Name'. If no modules are specified, then if
+%%     `Name' is also the name of an input module, that
+%%     module will be exported; otherwise the first listed module in
+%%     `Sources' will be exported. The default value is the
+%%     empty list.</dd>
+%%
+%%   <dt>`{export_all, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', this is equivalent to
+%%     listing all of the input modules in the `export'
+%%     option. The default value is `false'.</dd>
+%%
+%% <dt>`{file_attributes, Preserve}'</dt>
+%%     <dd><ul>
+%%       <li>`Preserve = yes | comment | no'</li>
+%%     </ul>
+%%     If the value is `yes', all file attributes
+%%     `-file(...)' in the input sources will be preserved in
+%%     the resulting code. If the value is `comment', they
+%%     will be turned into comments, but remain in their original
+%%     positions in the code relative to the other source code forms. If
+%%     the value is `no', all file attributes will be removed
+%%     from the code, unless they have attached comments, in which case
+%%     they will be handled as in the `comment' case. The
+%%     default value is `no'.</dd>
+%%
+%% <dt>`{no_banner, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', no banner comment will be
+%%     added at the top of the resulting module, even if the target
+%%     module does not have the same name as any of the input modules.
+%%     Instead, Igor will try to preserve the look of the module whose
+%%     code is at the top of the output. The default value is
+%%     `false'.</dd>
+%%
+%% <dt>`{no_headers, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', no header comments will be
+%%     added to the resulting module at the beginning of each section of
+%%     code that originates from a particular input module. The default
+%%     value is `false', which means that section headers are
+%%     normally added whenever more than two or more modules are
+%%     merged.</dd>
+%%
+%% <dt>`{no_imports, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', all
+%%     `-import(...)' declarations in the original code will
+%%     be expanded in the result; otherwise, as much as possible of the
+%%     original import declarations will be preserved. The default value
+%%     is `false'.</dd>
+%%
+%% <dt>`{notes, Notes}'</dt>
+%%     <dd><ul>
+%%       <li>`Notes = always | yes | no'</li>
+%%     </ul>
+%%     If the value is `yes', comments will be inserted where
+%%     important changes have been made in the code. If the value is
+%%     `always', <em>all</em> changes to the code will be
+%%     commented. If the value is `no', changes will be made
+%%     without comments. The default value is `yes'.</dd>
+%%
+%% <dt>`{redirect, [{atom(), atom()}]}'</dt>
+%%
+%%     <dd>Specifies a list of pairs of module names, representing a
+%%     mapping from old names to new. <em>The set of old names may not
+%%     include any of the names of the input modules.</em> All calls to
+%%     the listed old modules will be rewritten to refer to the
+%%     corresponding new modules. <em>The redirected calls will not be
+%%     further processed, even if the new destination is in one of the
+%%     input modules.</em> This option mainly exists to support module
+%%     renaming; cf. `rename/3'. The default value is the
+%%     empty list.</dd>
+%%
+%% <dt>`{safe, [atom()]}'</dt>
+%%
+%%     <dd>Specifies a list of names of input modules such that calls to
+%%     these "safe" modules may be turned into direct local calls, that
+%%     do not test for code replacement. Typically, this can be done for
+%%     e.g. standard library modules. If a module is "safe", it is per
+%%     definition also "static" (cf. below). The list may be empty. By
+%%     default, all involved modules <em>except the target module</em>
+%%     are considered "safe".</dd>
+%%
+%% <dt>`{static, [atom()]}'</dt>
+%%
+%%     <dd>Specifies a list of names of input modules which will be
+%%     assumed never to be replaced (reloaded) unless the target module
+%%     is also first replaced. The list may be empty. The target module
+%%     itself (which may also be one of the input modules) is always
+%%     regarded as "static", regardless of the value of this option. By
+%%     default, all involved modules are assumed to be static.</dd>
+%%
+%% <dt>`{tidy, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', the resulting code will be
+%%     processed using the `erl_tidy' module, which removes
+%%     unused functions and does general code cleanup. (See
+%%     `erl_tidy:module/2' for additional options.) The
+%%     default value is `true'.</dd>
+%%
+%% <dt>`{verbose, bool()}'</dt>
+%%
+%%     <dd>If the value is `true', progress messages will be
+%%     output while the program is running; the default value is
+%%     `false'.</dd>
+%% </dl>
+%%
+%% Note: The distinction between "static" and "safe" modules is
+%% necessary in order not to break the semantics of dynamic code
+%% replacement. A "static" source module will not be replaced unless the
+%% target module also is. Now imagine a state machine implemented by
+%% placing the code for each state in a separate module, and suppose
+%% that we want to merge this into a single target module, marking all
+%% source modules as static. At each point in the original code where a
+%% call is made from one of the modules to another (i.e., the state
+%% transitions), code replacement is expected to be detected. Then, if
+%% we in the merged code do not check at these points if the
+%% <em>target</em> module (the result of the merge) has been replaced,
+%% we can not be sure in general that we will be able to do code
+%% replacement of the merged state machine - it could run forever
+%% without detecting the code change. Therefore, all such calls must
+%% remain remote-calls (detecting code changes), but may call the target
+%% module directly.
+%%
+%% If we are sure that this kind of situation cannot ensue, we may
+%% specify the involved modules as "safe", and all calls between them
+%% will become local. Note that if the target module itself is specified
+%% as safe, "remote" calls to itself will be turned into local calls.
+%% This would destroy the code replacement properties of e.g. a typical
+%% server loop.
+%%
+%% @see create_stubs/2
+%% @see rename/3
+%% @see erl_tidy:module/2
+
+%% Currently, there is no run-time support in Erlang for detecting
+%% whether some module has been changed since the current module was
+%% loaded. Therefore, if a source module is specified as non-static, not
+%% much will be gained from merging: a call to a non-static module will
+%% remain a remote call using the old module name, even when it is
+%% performed from within the merged code. If that module is specified as
+%% exported, the old name could then refer to an auto-generated stub,
+%% redirecting the call back to the corresponding function in the target
+%% module. This could possibly be useful in some cases, but efficiency
+%% is not improved by such a transformation. If support for efficient
+%% testing for module updates is added to Erlang in future versions,
+%% code merging will be able to use local calls even for non-static
+%% source modules, opening the way for compiler optimisations over the
+%% module boundaries.
+
+%% Data structure for merging environment.
+
+-record(merge, {target,		% = atom()
+		sources,	% = ordset(atom())
+		export,		% = ordset(atom())
+		static,		% = ordset(atom())
+		safe,		% = ordset(atom())
+		preserved,	% = bool()
+		no_headers,	% = bool()
+		notes,		% = bool()
+		redirect,	% = dict(atom(), atom())
+		no_imports,	% = ordset(atom())
+		options		% = [term()]
+	       }).
+
+merge_sources(Name, Sources, Opts) ->
+    %% Prepare the options and the inputs.
+    Opts1 = Opts ++ [{export_all, false},
+		     {file_attributes, no},
+		     {no_imports, false},
+		     {notes, yes},
+		     tidy,
+		     {verbose, false}],
+    Trees = case Sources of
+		[] ->
+		    report_error("no sources to merge."),
+		    exit(badarg);
+		_ ->
+		    [if is_list(M) -> erl_syntax:form_list(M);
+			true -> M
+		     end
+		     || M <- Sources]
+	    end,
+    %% There must be at least one module to work with.
+    Modules = [get_module_info(T) || T <- Trees],
+    merge_sources_1(Name, Modules, Trees, Opts1).
+
+%% Data structure for keeping state during transformation.
+
+-record(state, {export}).
+
+state__add_export(Name, Arity, S) ->
+    S#state{export = sets:add_element({Name, Arity},
+				      S#state.export)}.
+
+merge_sources_1(Name, Modules, Trees, Opts) ->
+    %% Get the (nonempty) list of source module names, in the given
+    %% order. Multiple occurrences of the same source module name are
+    %% not accepted.
+    Ns = [M#module.name || M <- Modules],
+    case duplicates(Ns) of
+	[] ->
+	    ok;
+	Ns1 ->
+	    report_error("same module names repeated in input: ~p.",
+			 [Ns1]),
+	    exit(error)
+    end,
+    Sources = ordsets:from_list(Ns),
+    All = ordsets:add_element(Name, Sources),
+
+    %% Initialise the merging environment from the given options.
+    %%
+    %% If the `export' option is the empty list, then if the target
+    %% module is the same as one of the sources, that module will be
+    %% exported; otherwise the first listed source module is exported.
+    %% This simplifies use in most cases, and guarantees that the
+    %% generated module has a well-defined interface. If `export_all' is
+    %% `true', we expand it here by including the set of source module
+    %% names.
+    Es = case proplists:append_values(export, Opts) of
+	     [] ->
+		 case ordsets:is_element(Name, Sources) of
+		     true ->
+			 [Name];
+		     false ->
+			 [hd(Ns)]
+		 end;
+	     Es1 when is_list(Es1) ->
+		 ordsets:from_list(Es1)
+	 end,
+    Export = case proplists:get_bool(export_all, Opts) of
+		 false ->
+		     Es;
+		 true ->
+		     ordsets:union(Sources, Es)
+	     end,
+    check_module_names(Export, Sources, "declared as exported"),
+    verbose("modules exported from `~w': ~p.", [Name, Export], Opts),
+
+    %% The target module is always "static". (Particularly useful when
+    %% the target is the same as one of the source modules). It is
+    %% however not "safe" by default. If no modules are explicitly
+    %% specified as static, it is assumed that *all* are static.
+    Static0 = ordsets:from_list(proplists:append_values(static, Opts)),
+    case proplists:is_defined(static, Opts) of
+	false ->
+	    Static = All;
+	true ->
+	    Static = ordsets:add_element(Name, Static0)
+    end,
+    check_module_names(Static, All, "declared 'static'"),
+    verbose("static modules: ~p.", [Static], Opts),
+
+    %% If no modules are explicitly specified as "safe", it is assumed
+    %% that *all* source modules are "safe" except the target module and
+    %% those explicitly specified as "static".
+    Safe = case proplists:is_defined(safe, Opts) of
+	       false ->
+		   ordsets:subtract(Sources,
+				    ordsets:add_element(Name, Static0));
+	       true ->
+		   ordsets:from_list(
+		     proplists:append_values(safe, Opts))
+	   end,
+    check_module_names(Safe, All, "declared 'safe'"),
+    verbose("safe modules: ~p.", [Safe], Opts),
+
+    Preserved = (ordsets:is_element(Name, Sources)
+		 and ordsets:is_element(Name, Export))
+	or proplists:get_bool(no_banner, Opts),
+    NoHeaders = proplists:get_bool(no_headers, Opts),
+    Notes = proplists:get_value(notes, Opts, always),
+    Rs = proplists:append_values(redirect, Opts),
+    Redirect = case is_atom_map(Rs) of
+		   true ->
+		       Ms = ordsets:from_list([M || {M, _} <- Rs]),
+		       case ordsets:intersection(Sources, Ms) of
+			   [] ->
+			       ok;
+			   Ms1 ->
+			       report_error("cannot redirect calls to "
+					    "modules in input set: ~p.",
+					    [Ms1]),
+			       exit(error)
+		       end,
+		       dict:from_list(Rs);
+		   false ->
+		       report_error("bad value for `redirect' option: "
+				    "~P.",
+				    [Rs, 10]),
+		       exit(error)
+	       end,
+    NoImports = case proplists:get_bool(no_imports, Opts) of
+		    true ->
+			ordsets:from_list(Sources ++
+					  dict:fetch_keys(Redirect));
+		    false ->
+			ordsets:from_list(dict:fetch_keys(Redirect))
+		end,
+    Env = #merge{target = Name,
+		 sources = Sources,
+		 export = Export,
+		 safe = Safe,
+		 static = Static,
+		 preserved = Preserved,
+		 no_headers = NoHeaders,
+		 notes = Notes,
+		 redirect = Redirect,
+		 no_imports = NoImports,
+		 options = Opts},
+    merge_sources_2(Env, Modules, Trees, Opts).
+
+is_atom_map([{A1, A2} | As]) when is_atom(A1), is_atom(A2) ->
+    is_atom_map(As);
+is_atom_map([]) ->
+    true;
+is_atom_map(_) ->
+    false.
+
+check_module_names(Names, Sources, Txt) ->
+    case Names -- Sources of
+	[] ->
+	    ok;
+	Xs ->
+	    report_error("unknown modules ~s: ~p.", [Txt, Xs]),
+	    exit(error)
+    end.
+
+%% This function performs all the stages of the actual merge:
+
+merge_sources_2(Env, Modules, Trees, Opts) ->
+    %% Compute the merged name space and the list of renamings.
+    {Names, Renaming} = merge_namespaces(Modules, Env),
+    
+    %% Merge the source module descriptions, computing a structure
+    %% describing the resulting module, and a table of aliases which
+    %% must be expanded.
+    {Module, Expansions} = merge_info(Modules, Names, Renaming,
+				      Env),
+    
+    %% Merge the actual source code, also returning the "original
+    %% header" (for the first code section in the output).
+    St = #state{export = sets:new()},
+    {Tree, Header, St1} = merge_code(Trees, Modules, Expansions,
+				     Renaming, Env, St),
+
+    %% Filter out unwanted program forms and add a preamble to the code,
+    %% making a complete module.
+    Tree1 = erl_syntax:form_list([make_preamble(Module, Header,
+						Env, St1),
+				  filter_forms(Tree, Env)]),
+    
+    %% Tidy the final syntax tree (removing unused functions) and return
+    %% it together with the list of stub descriptors.
+    {tidy(Tree1, Opts), make_stubs(Modules, Renaming, Env)}.
+
+make_preamble(Module, Header, Env, St) ->
+    Name = Module#module.name,
+    Vars = Module#module.vars,
+    Extras = ordsets:from_list(sets:to_list(St#state.export)),
+    Exports = make_exports(Module#module.exports, Extras),
+    Imports = make_imports(Module#module.aliases),
+    Attributes = make_attributes(Module#module.attributes),
+    erl_syntax:form_list(module_header(Header, Name, Vars, Env)
+			 ++ Exports
+			 ++ Imports
+			 ++ Attributes).
+
+%% If the target preserves one of the source modules, we do not generate
+%% a new header, but use the original.
+
+module_header(Forms, Name, Vars, Env) ->
+    case Env#merge.preserved of
+	true ->
+	    update_header(Forms, Name, Vars);
+	false ->
+	    [comment([?COMMENT_BAR,
+		      "This module was formed by merging "
+		      "the following modules:",
+		      ""]
+		     ++ [lists:flatten(io_lib:fwrite("\t\t`~w'",
+						     [M]))
+			 || M <- Env#merge.sources]
+		     ++ ["",
+			 timestamp(),
+			 ""]),
+	     erl_syntax:attribute(erl_syntax:atom('module'),
+				  [erl_syntax:atom(Name)])]
+    end.
+
+update_header(Fs, Name, Vars) ->
+    [M | Fs1] = lists:reverse(Fs),
+    Ps = if Vars =:= none -> [];
+	    true -> [erl_syntax:list([erl_syntax:variable(V)
+				      || V <- Vars])]
+	 end,
+    M1 = rewrite(M, erl_syntax:attribute(erl_syntax:atom('module'),
+					 [erl_syntax:atom(Name) | Ps])),
+    lists:reverse([M1 | Fs1]).
+
+%% Some functions may have been noted as necessary to export (because of
+%% how they are called) even though the user did not specify that the
+%% modules in which these functions originated should be part of the
+%% interface of the resulting module.
+
+make_exports(Exports, Extras) ->
+    case ordsets:subtract(Extras, Exports) of
+	[] ->
+	    [make_export(Exports)];
+	Es ->
+	    [make_export(Exports),
+	     comment(["** The following exports "
+		      "are not official: **"]),
+	     make_export(Es)]
+    end.
+
+make_export(Names) ->
+    Es = [erl_syntax:arity_qualifier(erl_syntax:atom(F),
+				     erl_syntax:integer(A))
+	  || {F, A} <- Names],
+    if Es =:= [] ->
+	    comment(["** Nothing is officially exported "
+		    "from this module! **"]);
+       true ->
+	    erl_syntax:attribute(erl_syntax:atom('export'),
+				 [erl_syntax:list(Es)])
+    end.
+
+%% Any aliases that cannot be expressed using `import' (i.e. those not
+%% on the form `{F, {M, F}}') are ignored.
+
+make_imports(As) ->
+    %% First remove any auto-imports and "non-proper" imports from
+    %% the list.
+    As1 = [A || {F, {_M, F}} = A <- As, not is_auto_import(F)],
+    [make_import(M, Fs) || {M, Fs} <- group_imports(As1)].
+
+make_import(Module, Names) ->
+    Is = [erl_syntax:arity_qualifier(erl_syntax:atom(F),
+				     erl_syntax:integer(A))
+	  || {F, A} <- Names],
+    erl_syntax:attribute(erl_syntax:atom('import'),
+			 [erl_syntax:atom(Module),
+			  erl_syntax:list(Is)]).
+
+%% Group aliases by module.
+
+group_imports(Imports) ->
+    dict:to_list(
+      lists:foldl(
+	fun ({F, {M, F}}, D) ->
+		case dict:find(M, D) of
+		    {ok, V} ->
+			V1 = ordsets:add_element(F, V),
+			dict:store(M, V1, D);
+		    error ->
+			dict:store(M, [F], D)
+		end
+	end,
+	dict:new(), Imports)).
+
+
+%% ---------------------------------------------------------------------
+%% Making stub descriptors
+%%
+%% These are generated for all exported modules that are not the target
+%% module.
+
+make_stubs(Modules, Renaming, Env) ->
+    make_stubs_1(Modules, Renaming, Env).
+
+make_stubs_1([M | Ms], Renaming, Env) ->
+    Name = M#module.name,
+    if Name /= Env#merge.target ->
+	    case ordsets:is_element(Name, Env#merge.export) of
+		true ->
+		    [make_stub(M, Renaming(Name), Env)
+		     | make_stubs_1(Ms, Renaming, Env)];
+		false ->
+		    make_stubs_1(Ms, Renaming, Env)
+	    end;
+       true ->
+	    make_stubs_1(Ms, Renaming, Env)
+    end;
+make_stubs_1([], _, _) ->
+    [].
+
+make_stub(M, Map, Env) ->
+    Target = Env#merge.target,
+    Es = [{F, {Target, Map(F)}} || F <- M#module.exports],
+    {M#module.name, Es, M#module.attributes}.
+
+
+%% ---------------------------------------------------------------------
+%% Removing and/or out-commenting program forms. The returned form
+%% sequence tree is not necessarily flat.
+
+-record(filter, {records, file_attributes, attributes}).
+
+filter_forms(Tree, Env) ->
+    Forms = erl_syntax:form_list_elements(
+	      erl_syntax:flatten_form_list(Tree)),
+    erl_syntax:form_list(filter_forms_1(Forms, Env)).
+
+filter_forms_1(Forms, Env) ->
+    {Fs, _} = filter_forms_2(Forms, Env),
+    lists:reverse(Fs).
+
+filter_forms_2(Forms, Env) ->
+    FileAttrsOpt = proplists:get_value(file_attributes,
+				       Env#merge.options, comment),
+    %% Sanity check and translation of option value:
+    FileAttrs = case FileAttrsOpt of
+		    yes -> keep;
+		    no -> delete;
+		    comment -> kill;
+		    _ ->
+			report_error("invalid value for option "
+				     "`file_attributes': ~w.",
+				     [FileAttrsOpt]),
+			exit(error)
+		end,
+    Attrs = if length(Env#merge.sources) =:= 1 ->
+		    delete;    %% keeping the originals looks weird
+	       true ->
+		    kill
+	    end,
+    S = #filter{records = sets:new(),
+		file_attributes = FileAttrs,
+		attributes = Attrs},
+    lists:foldl(
+      fun (F, {Fs, S0}) ->
+	      case filter_form(F, S0) of
+		  {keep, S1} ->
+		      {[F | Fs], S1};    % keep
+		  {kill, S1} ->
+		      {[kill_form(F) | Fs], S1};    % kill
+		  {delete, S1} ->
+		      %% Remove, or kill if it has comments (only
+		      %% top-level comments are examined).
+		      case erl_syntax:has_comments(F) of
+			  false ->
+			      {Fs, S1};
+			  true ->
+			      {[kill_form(F) | Fs], S1}
+		      end
+	      end
+      end,
+      {[], S}, Forms).
+
+filter_form(F, S) ->
+    case erl_syntax_lib:analyze_form(F) of
+	{attribute, {'file', _}} ->
+	    {S#filter.file_attributes, S};
+	{attribute, {'module', _}} ->
+	    {delete, S};
+	{attribute, {'export', _}} ->
+	    {delete, S};
+	{attribute, {'import', _}} ->
+	    {delete, S};
+	{attribute, {'record', {R, _}}} ->
+	    Records = S#filter.records,
+	    case sets:is_element(R, Records) of
+		true ->
+		    {kill, S};    % already defined above
+		false ->
+		    S1 = S#filter{records =
+				  sets:add_element(R, Records)},
+		    {keep, S1}
+	    end;
+	{attribute, preprocessor} ->
+	    {keep, S};    %% keep all preprocessor attributes
+	{attribute, _} ->
+	    {S#filter.attributes, S};    %% handle all other attributes
+	{error_marker, _} ->
+	    {delete, S};
+	{warning_marker, _} ->
+	    {delete, S};
+	eof_marker ->
+	    {delete, S};    % these must be deleted!
+	_ ->
+	    {keep, S}    % keep all other Erlang forms
+    end.
+
+%% This out-comments (kills) a program form. Any top-level pre-comments
+%% are moved out, to avoid "nested" comments.
+
+kill_form(F) ->
+    F1 = erl_syntax:set_precomments(F, []),
+    F2 = erl_syntax_lib:to_comment(F1, ?KILL_PREFIX),
+    erl_syntax:set_precomments(F2,
+			       erl_syntax:get_precomments(F)).
+
+
+%% ---------------------------------------------------------------------
+%% Merging the name spaces of a set of modules. Returns the final set
+%% (see module `sets') of names and a total renaming function (atom())
+%% -> ({atom(), integer()}) -> {atom(), integer()}.
+%%
+%% Names are added in two passes, in order to avoid renaming the
+%% interface functions whenever possible: all exported functions are
+%% added to the name space before any nonexported are added, and
+%% "exported" modules are taken before any other. Thus, the order is:
+%%
+%%   - exported functions of exported modules
+%%   - exported functions of nonexported modules
+%%   - internal functions of exported modules
+%%   - internal functions of nonexported modules
+%%
+%% In fact, only the first group is important, but there might be some
+%% point in establishing the above order, for better readability of the
+%% final code.
+
+merge_namespaces(Modules, Env) ->
+    Export = Env#merge.export,
+    Split = fun (M) ->
+		    ordsets:is_element(M#module.name, Export)
+	    end,
+    {M1, M2} = split_list(Split, Modules),
+    R = dict:new(),
+    Acc = {sets:new(), R},
+    {M3, Acc1} = merge_namespaces_1(M1, Acc),
+
+    %% Detect and warn about renamed interface functions
+    {_, Maps0} = Acc1,
+    case [{M, dict:to_list(Map)}
+	  || {M, Map} <- dict:to_list(Maps0), dict:size(Map) =/= 0] of
+	[] ->
+	    ok;
+	Fs ->
+	    report_warning("interface functions renamed:\n\t~p.",
+			   [Fs])
+    end,
+    {M4, Acc2} = merge_namespaces_1(M2, Acc1),
+    Ms = M3 ++ M4,
+    Acc3 = merge_namespaces_2(Ms, Acc2),
+    {{Names, Maps}, _} = merge_namespaces_3(Ms, Acc3),
+    {Names, make_renaming_function(Maps)}.
+
+%% Adding exported names. (Note that the list gets a new temporary
+%% format also containing the exports.) This first step initialises the
+%% Maps "dict-of-dicts" structure.
+
+merge_namespaces_1(Modules, Acc) ->
+    lists:mapfoldl(
+      fun (Module, {Names, Maps}) ->
+	      Exports = sets:from_list(Module#module.exports),
+	      M = Module#module.name,
+	      {Names1, Map} = add_function_renamings(M, Exports, Names,
+						     dict:new()),
+	      Maps1 = dict:store(M, Map, Maps),
+	      {{Module, Exports}, {Names1, Maps1}}
+      end,
+      Acc, Modules).
+
+%% Adding nonexported names.
+
+merge_namespaces_2(Modules, Acc) ->
+    lists:foldl(
+      fun ({Module, Exports}, {Names, Maps}) ->
+	      Other = sets:subtract(
+			sets:from_list(Module#module.functions),
+			Exports),
+	      M = Module#module.name,
+	      Map = dict:fetch(M, Maps),
+	      {Names1, Map1} = add_function_renamings(M, Other, Names,
+						      Map),
+	      Maps1 = dict:store(M, Map1, Maps),
+	      {Names1, Maps1}
+      end,
+      Acc, Modules).
+
+%% Adding record names. We need to keep a global
+%% "record-definition-to-new-record-name" mapping RMap while doing this.
+
+merge_namespaces_3(Modules, Acc) ->
+    lists:foldl(
+      fun ({Module, _Exports}, {{Names, Maps}, RMap}) ->
+	      Records = Module#module.records,
+	      M = Module#module.name,
+	      Map = dict:fetch(M, Maps),
+	      {Names1, Map1, RMap1} = add_record_renamings(M, Records,
+							   Names, Map,
+							   RMap),
+	      Maps1 = dict:store(M, Map1, Maps),
+	      {{Names1, Maps1}, RMap1}
+      end,
+      {Acc, dict:new()}, Modules).
+
+%% This takes the set of added function names together with the existing
+%% name set, creates new function names where necessary, and returns the
+%% final name set together with the list of renamings.
+
+add_function_renamings(Module, New, Names, Map) ->
+    Clashes = sets:to_list(sets:intersection(New, Names)),
+    lists:foldl(
+      fun (F = {_, A}, {Names, Map}) when is_integer(A) ->
+	      F1 = new_function_name(Module, F, Names),
+	      {sets:add_element(F1, Names), dict:store(F, F1, Map)}
+      end,
+      {sets:union(New, Names), Map}, Clashes).
+
+%% This is similar to the above, but for record names. Note that we add
+%% both the record name and the whole definition to the namespace.
+
+add_record_renamings(Module, Records, Names, Map, RMap) ->
+    lists:foldl(
+      fun (N = {R, Fs}, {Names, Map, RMap}) ->
+	      case sets:is_element(?record_name(R), Names) of
+		  true ->
+		      %% The name is already in use.
+		      case sets:is_element(?record_name(N), Names) of
+			  true ->
+			      %% We have seen this definition before;
+			      %% make sure we use the same name.
+			      {R1, _} = remap_record_name(N, RMap),
+			      Map1 = dict:store(?record_name(R),
+						?record_name(R1), Map),
+			      {Names, Map1, RMap};
+			  false ->
+			      %% Redefinition of existing name. Create
+			      %% new name and set up renamings.
+			      N1 = {R1, _} = new_record_name(Module, R,
+							     Fs, Names),
+			      Map1 = dict:store(?record_name(R),
+						?record_name(R1), Map),
+			      RMap1 = dict:store(N, N1, RMap),
+			      Names1 = sets:add_element(?record_name(N1),
+							Names),
+			      {Names1, Map1, RMap1}
+		      end;
+		  false ->
+		      %% A previously unused record name.
+		      Names1 = sets:add_element(?record_name(R), Names),
+		      Names2 = sets:add_element(?record_name(N), Names1),
+		      {Names2, Map, RMap}
+	      end
+      end,
+      {Names, Map, RMap}, Records).
+
+remap_record_name(N, Map) ->
+    case dict:find(N, Map) of
+	{ok, N1} -> N1;
+	error -> N
+    end.
+
+%% This hides the implementation of the record namespace. Since Map
+%% yields identity for non-remapped names, the remapped names must be
+%% stored in wrapped form.
+
+map_record_name(R, Map) ->
+    ?record_name(R1) = Map(?record_name(R)),
+    R1.
+
+%% When we rename a function, we want the new name to be as close as
+%% possible to the old, and as informative as possible. Therefore, we
+%% first prefix it with the name of the originating module, followed by
+%% two underscore characters, and then if there still is a name clash,
+%% we suffix the name by "_N", where N is the smallest possible positive
+%% integer that does not cause a clash.
+
+new_function_name(M, {F, A}, Names) ->
+    Base = atom_to_list(M) ++ "__" ++ atom_to_list(F),
+    Name = {list_to_atom(Base), A},
+    case sets:is_element(Name, Names) of
+	false ->
+	    Name;
+	true ->
+	    new_function_name(1, A, Base, Names)
+    end.
+
+new_function_name(N, Arity, Base, Names) ->
+    Name = {list_to_atom(Base ++ "_" ++ integer_to_list(N)),
+	    Arity},
+    case sets:is_element(Name, Names) of
+	false ->
+	    Name;
+	true ->
+	    %% Increment counter and try again.
+	    new_function_name(N + 1, Arity, Base, Names)
+    end.
+
+%% This is pretty much the same as new_function_name, for now.
+
+new_record_name(M, R, Fs, Names) ->
+    Base = atom_to_list(M) ++ "__" ++ atom_to_list(R),
+    Name = {list_to_atom(Base), Fs},
+    case sets:is_element(?record_name(Name), Names) of
+	false ->
+	    Name;
+	true ->
+	    new_record_name_1(1, Base, Fs, Names)
+    end.
+
+new_record_name_1(N, Base, Fs, Names) ->
+    Name = {list_to_atom(Base ++ "_" ++ integer_to_list(N)), Fs},
+    case sets:is_element(?record_name(Name), Names) of
+	false ->
+	    Name;
+	true ->
+	    %% Increment counter and try again.
+	    new_record_name_1(N + 1, Base, Fs, Names)
+    end.
+
+%% This returns a *total* function from the set of module names to the
+%% set of *total* operators on function names, yielding identity for all
+%% function names that are not specified in the given partial map
+%% (ModuleName -> (Name -> Name)).
+
+make_renaming_function(Maps) ->
+    fun (Module) ->
+	    case dict:find(Module, Maps) of
+		{ok, Map} ->
+		    fun (Name) ->
+			    case dict:find(Name, Map) of
+				{ok, Name1} ->
+				    Name1;    % renamed
+				error ->
+				    Name    % identity
+			    end
+		    end;
+		error ->
+		    %% Other module - yield identity map.
+		    fun (Name) -> Name end
+	    end
+    end.
+
+
+%% ---------------------------------------------------------------------
+%% Merging module info records into a target module record, and finding
+%% necessary alias expansions. Returns `{Module, Expansions}' where
+%% `Expansions' has type `dict(ModuleName, dict(Alias, FullName))'
+
+merge_info(Modules, Names, Renaming, Env) ->
+    Forbid = sets:from_list(Env#merge.no_imports),
+    Expansions = alias_expansions(Modules, Names, Forbid),
+    Module = merge_info_1(Modules, Renaming, Expansions, Env),
+    {Module, Expansions}.
+
+merge_info_1(Modules, Renaming, Expansions, Env) ->
+    lists:foldl(
+      fun (M, A) ->
+	      Name = M#module.name,
+	      Map = Renaming(Name),
+	      Functions = join_functions(Map,
+					 M#module.functions,
+					 A#module.functions),
+	      Exports = join_exports(Env, Name, Map,
+				     M#module.exports,
+				     A#module.exports),
+	      Aliases = join_aliases(Name, Expansions,
+				     M#module.aliases,
+				     A#module.aliases),
+	      Attributes = join_attributes(Env, Name,
+					   M#module.attributes,
+					   A#module.attributes),
+	      Records = join_records(Map,
+				     M#module.records,
+				     A#module.records),
+	      A#module{functions = Functions,
+		       exports = Exports,
+		       aliases = Aliases,
+		       attributes = Attributes,
+		       records = Records}
+      end,
+      #module{name = Env#merge.target,
+	      functions = ordsets:new(),
+	      exports = ordsets:new(),
+	      aliases = ordsets:new(),
+	      attributes = ordsets:new(),
+	      records = ordsets:new()},
+      Modules).
+
+%% Functions must be renamed before including.
+
+join_functions(Map, Source, Target) ->
+    ordsets:union(ordsets:from_list([Map(A) || A <- Source]),
+		  Target).
+
+%% Exports also need renaming, and are kept only if their originating
+%% modules are exported.
+
+join_exports(Env, Name, Map, Source, Target) ->
+    case ordsets:is_element(Name, Env#merge.export) of
+	true ->
+	    ordsets:union(ordsets:from_list([Map(F)
+					     || F <- Source]),
+			  Target);
+	false ->
+	    Target
+    end.
+
+%% Aliases never need renaming; instead we always expand uses which
+%% could cause name clashes. We must then remove the expanded names from
+%% the imports of the target.
+
+join_aliases(Name, Expansions, Source, Target) ->
+    As = case dict:find(Name, Expansions) of
+	     {ok, As1} ->
+		 ordsets:from_list(dict:to_list(As1));
+	     error ->
+		 []
+	 end,
+    ordsets:union(ordsets:subtract(Source, As), Target).
+
+%% We only propagate attributes if the number of source modules is 1 or
+%% the source module has the same name as the resulting module.
+
+join_attributes(Env, Name, Source, Target) ->
+    if Env#merge.target =:= Name ->
+	    ordsets:union(Source, Target);
+       true ->
+	    if length(Env#merge.sources) =:= 1 ->
+		    ordsets:union(Source, Target);
+	       true ->
+		    Target
+	    end
+    end.
+
+%% The final record info in itself is not used at present, but we
+%% compute the join anyway. We apply renaming to records much like we do
+%% to functions, but records have a separate namespace.
+
+join_records(Map, Source, Target) ->
+    Renamed = [{map_record_name(R, Map), Fs} || {R, Fs} <- Source],
+    ordsets:union(ordsets:from_list(Renamed), Target).
+
+%% This finds aliases that are in conflict or are for other reasons
+%% necessary to expand while transforming the code later. It is assumed
+%% that each module is in itself correct, and thus does not contain
+%% conflicting definitions of the same alias.
+%%
+%% We could of course simply say that *all* aliases, without exception,
+%% should be expanded, but such a big change in the style of the code
+%% should not be done unless the user explicitly specifies it.
+%%
+%% The returned `Expansions' is a dictionary (module `dict') mapping
+%% each module name in `Modules' to a dictionary which maps those
+%% aliases to be expanded for that module to their corresponding full
+%% names.
+%%
+%% Aliases are filtered according to the following rules:
+%%
+%%	1. If a name is defined (in some source module) as an alias of a
+%%	name `M:...', where `M' is any of the source modules(*), then
+%%	the definition of that alias should be removed, and all its uses
+%%	(in the same module as the definition) be expanded.
+%%
+%%	2. Then, if a name is defined (in some source module) as an
+%%	alias, but the name occurs in the name space of the resulting
+%%	module, then the definition should be removed and all uses (in
+%%	the same module) expanded.
+%%
+%%	3. Finally, if a name has two or more distinct alias definitions
+%%	in the source modules, then all definitions of that alias should
+%%	be removed and all uses (in all modules) expanded. (We remove
+%%	all definitions mainly for symmetry.)
+%%
+%%	(*) It is actually possible for an alias to refer to the module
+%%	in which it is itself defined. However, since we also in this
+%%	case want to expand all uses, we don't have to do any extra work
+%%	to handle it.
+
+%% The filtering is done in two stages.
+
+alias_expansions(Modules, Names, Forbid) ->
+    Table = alias_expansions_1(Modules, Forbid, Names),
+    alias_expansions_2(Modules, Table).
+
+%% First consider each alias in isolation.
+
+alias_expansions_1(Modules, Forbid, Names) ->
+    lists:foldl(
+      fun (M, T) ->
+	      Map = lists:foldl(
+		      fun ({A, F}, T1) ->
+			      case keep_alias(A, F, Forbid, Names)
+				  of
+				  true ->
+				      T1;
+				  false ->
+				      dict:store(A, F, T1)
+			      end
+		      end,
+		      dict:new(), M#module.aliases),
+	      dict:store(M#module.name, Map, T)
+      end,
+      dict:new(), Modules).
+
+keep_alias(A, {M, _}, Forbid, Names) ->
+    case sets:is_element(M, Forbid) of
+	true ->
+	    false;
+	false ->
+	    not sets:is_element(A, Names)
+    end.
+
+%% In this second stage, we resolve any conflicts that may remain
+%% because of distinct source modules still containing distinct alias
+%% definitions of the same name - in that case we remove *all* of them
+%% (mainly for symmetry).
+
+alias_expansions_2(Modules, Table) ->
+    %% Get the set of all alias definitions in all modules (collapsing
+    %% duplicated but equivalent definitions).
+    Aliases = lists:foldl(
+		fun (M, A) ->
+			ordsets:union(A, M#module.aliases)
+		end,
+		ordsets:new(), Modules),
+    
+    %% Get the set of names with multiple (distinct) definitions.
+    Names = duplicates([F || {F, _} <- Aliases]),
+    
+    %% Go through all aliases in all source modules and add necessary
+    %% entries to the expansion-table. We expect that there is an entry
+    %% in the table here for each module.
+    lists:foldl(
+      fun (M, T) ->
+	      N = M#module.name,
+	      lists:foldl(
+		fun ({A, F}, T1) ->
+			case ordsets:is_element(A, Names) of
+			    true ->
+				T2 = dict:fetch(N, T1),
+				dict:store(N,
+					   dict:store(A, F, T2),
+					   T1);
+			    false ->
+				T1
+			end
+		end,
+		T, M#module.aliases)
+      end,
+      Table, Modules).
+
+
+%% ---------------------------------------------------------------------
+%% Merging the source code.
+
+%% Data structure for code transformation environment.
+
+-record(code, {module,		% = atom()
+	       target,		% = atom()
+	       sources,		% = ordset(atom())
+	       static,		% = ordset(atom())
+	       safe,		% = ordset(atom())
+	       preserved,	% = bool()
+	       no_headers,	% = bool()
+	       notes,		% = bool()
+	       map,		% = ({atom(), int()}) -> {atom(), int()}
+	       renaming,	% = (atom()) -> ({atom(), int()}) ->
+				%               {atom(), int()}
+	       expand,		% = dict({atom(), int()},
+				%      {atom(), {atom(), int()}})
+	       redirect		% = dict(atom(), atom())
+	      }).
+
+%% `Trees' must be a list of syntax trees of type `form_list'. The
+%% result is a pair `{Result, Header}' where `Result' is a `form_list'
+%% tree representing the merged code, and if the `preserved' flag is
+%% set, `Header' is the list of forms up to and including the first
+%% `-module(...)' declaration, but stripped of any `-file(...)'
+%% attributes - otherwise `Header' is an empty list.
+
+merge_code(Trees, Modules, Expansions, Renaming, Env, St) ->
+    Env1 = #code{target = Env#merge.target,
+		 sources = sets:from_list(Env#merge.sources),
+		 static = sets:from_list(Env#merge.static),
+		 safe = sets:from_list(Env#merge.safe),
+		 preserved = Env#merge.preserved,
+		 no_headers = Env#merge.no_headers,
+		 notes = Env#merge.notes,
+		 redirect = Env#merge.redirect,
+		 renaming = Renaming},
+    Code = order_code(Modules, Trees, Env1),
+    {Code1, Header} = case Env1#code.preserved of
+			  true ->
+			      take_header(Code);
+			  false ->
+			      {Code, erl_syntax:form_list([])}
+		      end,
+    {Forms, St1} = merge_code_1(Code1, Expansions, Env1, St),
+    Tree = erl_syntax:form_list(Forms),
+    {Tree, Header, St1}.
+
+merge_code_1(Code, Expansions, Env, St) ->
+      lists:foldr(
+	fun ({Module, T}, {Acc, St0}) ->
+		M = Module#module.name,
+		Expand = case dict:find(M, Expansions) of
+			     {ok, Dict} -> Dict;
+			     error -> dict:new()
+			 end,
+		Env1 = Env#code{module = M,
+				map = (Env#code.renaming)(M),
+				expand = Expand},
+		{T1, St1} = transform(T, Env1, St0),
+		{[section_header(M, T1, Env1) | Acc], St1}
+	end,
+	{[], St}, Code).
+
+%% Pair module info and source code, in the order we want, and flatten
+%% the form lists. If the name of the target is the same as one of the
+%% source modules, and the result should preserve the original module,
+%% the code for that module should be first in the output.
+
+order_code(Modules, Trees, Env) ->
+    order_code(Modules, Trees, {}, [], Env).
+
+order_code([M | Ms], [T | Ts], First, Rest, Env) ->
+    T1 = erl_syntax:flatten_form_list(T),
+    case (M#module.name =:= Env#code.target) and
+	Env#code.preserved of
+	true ->
+	    order_code(Ms, Ts, {M, T1}, Rest, Env);
+	false ->
+	    order_code(Ms, Ts, First, [{M, T1} | Rest], Env)
+    end;
+order_code([], [], First, Rest, _Env) ->
+    Rest1 = lists:reverse(Rest),
+    case First of
+	{} ->
+	    Rest1;
+	M ->
+	    [M | Rest1]
+    end.
+
+%% Extracting the "original" header (the `-module(...)' declaration is
+%% sure to exist).
+
+take_header([{M, T} | Ms]) ->
+    Fs = erl_syntax:form_list_elements(T),
+    {Header, Fs1} = take_header_1(Fs, []),
+    T1 = erl_syntax:form_list(Fs1),
+    {[{M, T1} | Ms], Header}.
+
+take_header_1([F | Fs], As) ->
+    case erl_syntax_lib:analyze_form(F) of
+	{'attribute', {'module', _}} ->
+	    {lists:reverse([F | As]), Fs};    % done
+	{'attribute', {'file', _}} ->
+	    take_header_1(Fs, As);    % discard
+	_ ->
+	    take_header_1(Fs, [F | As])    % keep
+    end.
+
+section_header(Name, Tree, Env) ->
+    N = sets:size(Env#code.sources),
+    if N > 1, Name /= Env#code.target, Env#code.notes /= no,
+       Env#code.no_headers /= true ->
+	    Text = io_lib:fwrite("The following code stems "
+				 "from module `~w'.", [Name]),
+	    Header = comment([?COMMENT_BAR, "",
+			      lists:flatten(Text), ""]),
+	    erl_syntax:form_list([Header, Tree]);
+       true ->
+	    Tree
+    end.
+
+transform(Tree, Env, St) ->
+    case erl_syntax:type(Tree) of
+	application ->
+	    transform_application(Tree, Env, St);
+	attribute ->
+	    transform_attribute(Tree, Env, St);
+  	function ->
+  	    transform_function(Tree, Env, St);
+ 	implicit_fun ->
+ 	    transform_implicit_fun(Tree, Env, St);
+  	rule ->
+  	    transform_rule(Tree, Env, St);
+  	record_expr ->
+  	    transform_record(Tree, Env, St);
+  	record_index_expr ->
+  	    transform_record(Tree, Env, St);
+  	record_access ->
+  	    transform_record(Tree, Env, St);
+	_ ->
+	    default_transform(Tree, Env, St)
+    end.
+
+default_transform(Tree, Env, St) ->
+    case erl_syntax:subtrees(Tree) of
+	[] ->
+	    {Tree, St};
+	Gs ->
+	    {Gs1, St1} = transform_1(Gs, Env, St),
+	    Tree1 = rewrite(Tree, erl_syntax:make_tree(
+				    erl_syntax:type(Tree),
+				    Gs1)),
+	    {Tree1, St1}
+    end.
+
+transform_1([G | Gs], Env, St) ->
+    {G1, St1} = transform_list(G, Env, St),
+    {Gs1, St2} = transform_1(Gs, Env, St1),
+    {[G1 | Gs1], St2};
+transform_1([], _Env, St) ->
+    {[], St}.
+
+transform_list([T | Ts], Env, St) ->
+    {T1, St1} = transform(T, Env, St),
+    {Ts1, St2} = transform_list(Ts, Env, St1),
+    {[T1 | Ts1], St2};
+transform_list([], _Env, St) ->
+    {[], St}.
+
+%% Renaming function definitions
+
+transform_function(T, Env, St) ->
+    {T1, St1} = default_transform(T, Env, St),
+    F = erl_syntax_lib:analyze_function(T1),
+    {V, Text} = case (Env#code.map)(F) of
+		    F ->
+			%% Not renamed
+			{none, []};
+		    {Atom, _Arity} ->
+			%% Renamed
+			Cs = erl_syntax:function_clauses(T1),
+			N = rename_atom(
+			      erl_syntax:function_name(T1),
+			      Atom),
+			T2 = erl_syntax:function(N, Cs),
+			{{value, T2}, renaming_note(Atom)}
+		end,
+    {maybe_modified(V, T1, 2, Text, Env), St1}.
+
+renaming_note(Name) ->
+    [lists:flatten(io_lib:fwrite("renamed function to `~w'",
+				 [Name]))].
+
+rename_atom(Node, Atom) ->
+    rewrite(Node, erl_syntax:atom(Atom)).
+
+%% Renaming Mnemosyne rules (just like function definitions)
+
+transform_rule(T, Env, St) ->
+    {T1, St1} = default_transform(T, Env, St),
+    F = erl_syntax_lib:analyze_rule(T1),
+    {V, Text} = case (Env#code.map)(F) of
+		    F ->
+			%% Not renamed
+			{none, []};
+		    {Atom, _Arity} ->
+			%% Renamed
+			Cs = erl_syntax:rule_clauses(T1),
+			N = rename_atom(
+			      erl_syntax:rule_name(T1),
+			      Atom),
+			T2 = rewrite(T1,
+				     erl_syntax:rule(N, Cs)),
+			{{value, T2}, renaming_note(Atom)}
+		end,
+    {maybe_modified(V, T1, 2, Text, Env), St1}.
+
+%% Renaming "implicit fun" expressions (done quietly).
+
+transform_implicit_fun(T, Env, St) ->
+    {T1, St1} = default_transform(T, Env, St),
+    F = erl_syntax_lib:analyze_implicit_fun(T1),
+    {V, Text} = case (Env#code.map)(F) of
+		    F ->
+			%% Not renamed
+			{none, []};
+		    {Atom, Arity} ->
+			%% Renamed
+			N = rewrite(
+			      erl_syntax:implicit_fun_name(T1),
+			      erl_syntax:arity_qualifier(
+				erl_syntax:atom(Atom),
+				erl_syntax:integer(Arity))),
+			T2 = erl_syntax:implicit_fun(N),
+			{{value, T2}, ["function was renamed"]}
+		end,
+    {maybe_modified_quiet(V, T1, 2, Text, Env), St1}.
+
+%% Transforming function applications
+
+transform_application(T, Env, St) ->
+    %% We transform the arguments first, so we can concentrate on the
+    %% application itself after that point.
+    {As, St1} = transform_list(
+		  erl_syntax:application_arguments(T),
+		  Env, St),
+    F = erl_syntax:application_operator(T),
+
+    %% See if the operator is an explicit function name.
+    %% (Usually, this will be the case.)
+    case catch {ok, erl_syntax_lib:analyze_function_name(F)} of
+	{ok, Name} ->
+	    transform_application_1(Name, F, As, T, Env, St1);
+	syntax_error ->
+	    %% Oper is not a function name, but might be any other
+	    %% expression - we just visit it and reassemble the
+	    %% application.
+	    %% We do not handle applications of tuples `{M, F}'.
+	    {F1, St2} = transform(F, Env, St1),
+	    {rewrite(T, erl_syntax:application(F1, As)), St2};
+	{'EXIT', R} ->
+	    exit(R);
+	R ->
+	    throw(R)
+    end.
+
+%% At this point we should have an explicit function name, which might
+%% or might not be qualified by a module name.
+
+transform_application_1(Name, F, As, T, Env, St) ->
+    %% Before doing anything else, we must unfold any uses of aliases
+    %% whose definitions have been killed.
+    Arity = length(As),
+    {Name1, F1} = expand_operator(Name, Arity, F, Env),
+    F2 = maybe_modified_quiet(F1, F, 7, ["unfolded alias"], Env),
+    {V, St1} = transform_application_2(Name1, Arity, F2, As, Env,
+				       St),
+    T1 = rewrite(T, erl_syntax:application(F2, As)),
+    T3 = case V of
+	     none ->
+		 T1;
+	     {value, {T2, Depth, Message}} ->
+		 maybe_modified_quiet({value, T2}, T1, Depth,
+				      Message, Env)
+	 end,
+    {T3, St1}.
+
+%% Here, Name has been expanded if necessary (if so, this is also
+%% reflected by F), and As have been transformed. We should return
+%% `{none, State}' if no further rewriting is necessary, and otherwise
+%% `{{value, {Tree, Depth, Message}}, State}', where `Depth' and
+%% `Message' are to be passed to `maybe_modified'.
+
+transform_application_2(Name, Arity, F, As, Env, St)
+  when is_atom(Name) ->
+    transform_atom_application(Name, Arity, F, As, Env, St);
+transform_application_2({M, N}, Arity, F, As, Env, St)
+  when is_atom(M), is_atom(N) ->
+    transform_qualified_application(M, N, Arity, F, As, Env, St);
+transform_application_2(_Name, _Arity, _F, _As, _Env, St) ->
+    {none, St}.    % strange name - do nothing.
+
+expand_operator(Name, Arity, _F, Env) when is_atom(Name) ->
+    %% An unqualified function name - must be looked up. However, we
+    %% must first check that it is not an auto-imported name - these
+    %% have precedence over normal imports. We do a sanity check on the
+    %% found arity.
+    case is_auto_import({Name, Arity}) of
+	true ->
+	    {Name, none};    % auto-import - never expand.
+	false ->
+	    case dict:find({Name, Arity}, Env#code.expand) of
+		{ok, {M, {N, A}}} when A =:= Arity ->
+		    %% Expand to a qualified name.
+		    F1 = erl_syntax:module_qualifier(
+			   erl_syntax:atom(M),
+			   erl_syntax:atom(N)),
+		    {{M, N}, {value, F1}};
+		error ->
+		    %% Not in the table - leave it unchanged
+		    {Name, none}
+	    end
+    end;
+expand_operator(Name, _Arity, _F, _Env) ->
+    %% Qualified function name - leave it unchanged
+    {Name, none}.
+
+%% Transforming an application of a named function without module
+%% qualifier (often misleadingly called "local" applications). Note that
+%% since the `apply', `spawn' and `spawn_link' functions are implicitly
+%% imported (from module `erlang'), applications of these names cannot
+%% refer to functions defined in the source code.
+
+transform_atom_application(Name, Arity, F, As, Env, St) ->
+    %% Catch applications of `apply' and `spawn'.
+    case {Name, Arity} of
+	{'apply', 2} ->
+	    warning_apply_2(Env#code.module, Env#code.target),
+	    {none, St};
+	{'apply', 3} ->
+	    transform_apply_call(F, As, Env, St);
+	{'spawn', 3} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'spawn', 4} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'spawn_link', 3} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'spawn_link', 4} ->
+	    transform_spawn_call(F, As, Env, St);
+	_ ->
+	    %% A simple call of an unqualified function name - just
+	    %% remap the name as necessary. Auto-imported names may not
+	    %% be changed - the call never refers to a local function.
+	    %% We do a sanity check on the arity.
+	    case is_auto_import({Name, Arity}) of
+		true ->
+		    {none, St};    % auto-import - do not change.
+		false ->
+		    case (Env#code.map)({Name, Arity}) of
+			{N, A} when N =:= Name, A =:= Arity ->
+			    %% Not changed.
+			    {none, St};
+			{N, A} when A =:= Arity ->
+			    %% The callee (in the current module)
+			    %% was renamed.
+			    F1 = rewrite(F, erl_syntax:atom(N)),
+			    T = erl_syntax:application(F1, As),
+			    V = {T, 2, ["callee was renamed"]},
+			    {{value, V}, St}
+		    end
+	    end
+    end.
+
+%% Transforming an application of an explicitly named function qualified
+%% with an (also explicit) module name. (Often called "remote"
+%% applications.)
+
+transform_qualified_application(Module, Name, Arity, F, As, Env, St) ->
+    %% Catch applications of `apply' and `spawn'.
+    case {Module, Name, Arity} of
+	{'erlang', 'apply', 2} ->
+	    warning_apply_2(Env#code.module, Env#code.target),
+	    {none, St};
+	{'erlang', 'apply', 3} ->
+	    transform_apply_call(F, As, Env, St);
+	{'erlang', 'spawn', 3} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'erlang', 'spawn', 4} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'erlang', 'spawn_link', 3} ->
+	    transform_spawn_call(F, As, Env, St);
+	{'erlang', 'spawn_link', 4} ->
+	    transform_spawn_call(F, As, Env, St);
+	_ ->
+	    case erlang:is_builtin(Module, Name, Arity) of
+		false ->
+		    transform_qualified_application_1(
+		      Module, Name, Arity, F, As, Env, St);
+		true ->
+		    {none, St}
+	    end
+    end.
+
+transform_qualified_application_1(Module, Name, Arity, F, As, Env,
+				  St) ->
+    MakeLocal = fun (N) ->
+			F1 = rewrite(F, erl_syntax:atom(N)),
+			erl_syntax:application(F1, As)
+		end,
+    MakeRemote = fun () ->
+			 erl_syntax:application(F, As)
+		 end,
+    MakeDynamic = fun(M, N) ->
+			  F1 = erl_syntax:module_qualifier(
+				 erl_syntax:atom(M),
+				 erl_syntax:atom(N)),
+			  F2 = rewrite(F, F1),
+			  erl_syntax:application(F2, As)
+		  end,
+    localise(Module, Name, Arity, MakeLocal, MakeRemote,
+	     MakeDynamic, 3, Env, St).
+
+%% For an `apply/3' call, if we know the called module and function
+%% names, and the number of arguments, then we can rewrite it to a
+%% direct remote call - and if we do not, there is nothing we can
+%% change.
+
+transform_apply_call(F, As, Env, St) ->
+    [Module, Name, List] = As,
+    case (erl_syntax:type(Module) =:= atom)
+	and (erl_syntax:type(Name) =:= atom)
+	and erl_syntax:is_proper_list(List) of
+	true ->
+	    transform_apply_call_1(Module, Name, List, F, As, Env,
+				   St);
+	false ->
+	    %% We can't get enough information about the
+	    %% arguments to the `apply' call, so we do nothing
+	    %% but warn.
+	    warning_unsafe_call(apply, Env#code.module,
+				Env#code.target),
+	    {none, St}
+    end.
+
+%% Rewrite the apply-call to a static qualified call and handle that
+%% instead.
+
+transform_apply_call_1(Module, Name, List, F, _As, Env, St) ->
+    F1 = rewrite(F, erl_syntax:module_qualifier( Module, Name)),
+    As1 = erl_syntax:list_elements(List),
+    M = erl_syntax:atom_value(Module),
+    N = erl_syntax:atom_value(Name),
+    A = length(As1),
+    transform_qualified_application_1(M, N, A, F1, As1, Env, St).
+
+%% `spawn' and `spawn_link' (with arity 3 or 4) are very much like
+%% `apply/3', but there could be an extra `Node' argument. Note that `F'
+%% below can represent both `spawn' and `spawn_link'.
+
+transform_spawn_call(F, As, Env, St) ->
+    case As of
+	[Module, Name, List] ->
+	    MakeSpawn = fun (As1) ->
+				erl_syntax:application(F, As1)
+			end,
+	    transform_spawn_call_1(Module, Name, List, MakeSpawn,
+				   Env, St);
+	[Node, Module, Name, List] ->
+	    MakeSpawn = fun (As1) ->
+				erl_syntax:application(
+				  F, [Node | As1])
+			end,
+	    transform_spawn_call_1(Module, Name, List, MakeSpawn,
+				   Env, St)
+    end.
+
+%% Here, we can treat all dynamic-lookup spawns like `spawn/3'.
+
+transform_spawn_call_1(Module, Name, List, MakeSpawn, Env, St) ->
+    case (erl_syntax:type(Module) =:= atom)
+	and (erl_syntax:type(Name) =:= atom)
+	and erl_syntax:is_proper_list(List)
+	of
+	true ->
+	    transform_spawn_call_2(Module, Name, List, MakeSpawn,
+				   Env, St);
+	_ ->
+	    %% We can't get enough information about the arguments to
+	    %% the `spawn' call, so we do nothing but warn.
+	    warning_unsafe_call(spawn, Env#code.module,
+				Env#code.target),
+	    {none, St}
+    end.
+
+transform_spawn_call_2(Module, Name, List, MakeSpawn, Env, St) ->
+    As = erl_syntax:list_elements(List),
+    Arity = length(As),
+    MakeLocal = fun (N) ->
+			%% By using `spawn-a-fun', we do not have to
+			%% force the callee to be exported.
+			A = rewrite(Name, erl_syntax:atom(N)),
+			B = erl_syntax:application(A, As),
+			C = erl_syntax:clause([], [B]),
+			F = erl_syntax:fun_expr([C]),
+			MakeSpawn([F])
+		end,
+    MakeRemote = fun () ->
+			 MakeSpawn([Module, Name, List])
+		 end,
+    MakeDynamic = fun (M, N) ->
+			  F = rewrite(Name, erl_syntax:atom(N)),
+			  MakeSpawn([erl_syntax:atom(M), F, List])
+		  end,
+    localise(erl_syntax:atom_value(Module),
+	     erl_syntax:atom_value(Name),
+	     Arity, MakeLocal, MakeRemote, MakeDynamic,
+	     4, Env, St).
+
+%% MakeLocal = (atom()) -> syntaxTree()
+%% MakeRemote = () -> syntaxTree()
+%% MakeDynamic = (atom(), atom()) -> syntaxTree()
+%% localise(...) -> {none, state()} | {{value, V}, State}
+
+localise(Module, Name, Arity, MakeLocal, MakeRemote, MakeDynamic,
+	 Depth, Env, St) ->
+    %% Is the callee in one of the source modules?
+    case sets:is_element(Module, Env#code.sources) of
+	false ->
+	    case dict:find(Module, Env#code.redirect) of
+		{ok, Module1} ->
+		    T = MakeDynamic(Module1, Name),
+		    V = {T, Depth, ["redirected call"]},
+		    {{value, V}, St};
+		error ->
+		    {none, St}    % Nothing needs doing.
+	    end;
+	true ->
+	    %% Remap the name of the callee, as necessary. Do a sanity
+	    %% check on the arity.
+	    Map = (Env#code.renaming)(Module),
+	    Name1 = case Map({Name, Arity}) of
+			{N, A} when A =:= Arity ->
+			    N
+		    end,
+
+	    %% See if the callee module is "safe" and/or "static".
+	    Safe = sets:is_element(Module, Env#code.safe),
+	    Static = (sets:is_element(Module, Env#code.static)
+		      or Safe),
+
+	    %% Select what kind of code to generate for the call:
+	    case Static of
+		false ->
+		    %% (This also implies that the called module is not
+		    %% the target module - which is always "static" -
+		    %% and that it is not "safe".) The called module
+		    %% could be replaced dynamically, independent of the
+		    %% target module, so we must protect the localised
+		    %% call. We strip all comments from the localised
+		    %% code, to avoid getting the same comments twice.
+		    L = MakeLocal(Name1),
+		    L1 = erl_syntax_lib:strip_comments(L),
+		    R = MakeRemote(),
+		    {T, Text} = protect_call(Module, L1, R),
+		    V = {T, Depth, Text},
+		    {{value, V}, St};
+		true ->
+		    %% In this case, the called module is never replaced
+		    %% unless the target module also is. (N.B.: These
+		    %% might be the same module.)
+		    case Safe of
+			false ->
+			    %% The normal code replacement semantics
+			    %% must be preserved here, so the generated
+			    %% call must be qualified with the name of
+			    %% the target module. (We assume this is
+			    %% efficiently compiled even if we do not
+			    %% insert an explicit "latest version"
+			    %% test.)
+			    Target = Env#code.target,
+			    case Module =:= Target of
+				true ->
+				    %% Already calling the target module
+				    %% - do not insert irritating notes.
+				    {none, St};
+				false ->
+				    %% We must ensure that the function
+				    %% is exported.
+				    St1 = state__add_export(Name1,
+							    Arity, St),
+				    T = MakeDynamic(Target, Name1),
+				    Text = ["localised call"],
+				    V = {T, Depth, Text},
+				    {{value, V}, St1}
+			    end;
+			true ->
+			    %% The call is regarded as safe to localise
+			    %% completely. Code replacement will in
+			    %% general not be detected (except for
+			    %% spawn/apply).
+			    T = MakeLocal(Name1),
+			    Text = ["localised safe call"],
+			    V = {T, Depth, Text},
+			    {{value, V}, St}
+		    end
+	    end
+    end.
+
+%%% %% This creates a test on whether there is a later loaded version of
+%%% %% Module: if not, select the `Local' expression, otherwise the `Remote'
+%%% %% expression. We knowingly duplicate code here, to allow better
+%%% %% optimisations, but we never duplicate work.
+%%%
+%%% protect_call(Module, Local, Remote) ->
+%%%     T = erl_syntax:if_expr(
+%%% 	  [erl_syntax:clause([erl_syntax:application(
+%%% 				erl_syntax:atom('not_replaced'),
+%%% 				[erl_syntax:atom(Module)])],
+%%% 			     [Local]),
+%%% 	   erl_syntax:clause([erl_syntax:atom('true')],
+%%% 			     [Remote])]),
+%%%     {T, ["localised dynamic call"]}.
+
+%% This "protects" a localised call by letting it remain a remote call.
+
+protect_call(_Module, _Local, Remote) ->
+    {Remote, ["dynamic call"]}.
+
+%% Renaming record declarations
+
+transform_attribute(T, Env, St) ->
+    {T1, St1} = TSt1 = default_transform(T, Env, St),
+    case erl_syntax_lib:analyze_attribute(T1) of
+	{record, {R, _}} ->
+	    F = fun(R) ->
+			[_ | As] = erl_syntax:attribute_arguments(T1),
+			erl_syntax:attribute(
+			  erl_syntax:attribute_name(T1),
+			  [erl_syntax:atom(R) | As])
+		end,
+	    {V, Text} = rename_record(R, F, Env),
+	    {maybe_modified(V, T1, 2, Text, Env), St1};
+	_ ->
+	    TSt1
+    end.
+
+%% This handles renaming of records.
+
+transform_record(T, Env, St) ->
+    {T1, St1} = TSt1 = default_transform(T, Env, St),
+    X = case catch erl_syntax_lib:analyze_record_expr(T1) of
+	    {record_expr, {R, _}} ->
+		F = fun (R) ->
+			    erl_syntax:record_expr(
+			      erl_syntax:record_expr_argument(T1),
+			      erl_syntax:atom(R),
+			      erl_syntax:record_expr_fields(T1))
+		    end,
+		{R, F};
+	    {record_index_expr, {R, _}} ->
+		F = fun (R) ->
+			    erl_syntax:record_index_expr(
+			      erl_syntax:atom(R),
+			      erl_syntax:record_index_expr_field(T1))
+		    end,
+		{R, F};
+	    {record_access, {R, _}} ->
+		F = fun (R) ->
+			    erl_syntax:record_access(
+			      erl_syntax:record_access_argument(T1),
+			      erl_syntax:atom(R),
+			      erl_syntax:record_access_field(T1))
+		    end,
+		{R, F};
+	    _Type ->
+		false
+	end,
+    case X of
+	{R1, F1} ->
+	    {V, Text} = rename_record(R1, F1, Env),
+	    {maybe_modified(V, T1, 1, Text, Env), St1};
+	false ->
+	    TSt1
+    end.
+
+rename_record(R, F, Env) ->
+    case map_record_name(R, Env#code.map) of
+	R ->
+	    %% Not renamed
+	    {none, []};
+	R1 ->
+	    %% Renamed
+	    {{value, F(R1)}, ["record was renamed"]}
+    end.
+
+%% Maybe-rewriting Node, adding modification notes.
+
+%% This is for non-primary modifications; they are not commented unless
+%% the `notes' option is set to `always'.
+
+maybe_modified_quiet(V, Node, Depth, Message, Env) ->
+    case Env#code.notes of
+	always ->
+	    maybe_modified_1(V, Node, Depth, Message, yes);
+	_ ->
+	    maybe_modified_1(V, Node, Depth, Message, no)
+    end.
+
+%% This is for important notes; they are only disabled if the `notes'
+%% option is set to `no'.
+
+maybe_modified(V, Node, Depth, Message, Env) ->
+    maybe_modified_1(V, Node, Depth, Message, Env#code.notes).
+
+maybe_modified_1(none, Node, _Depth, _Message, _Notes) ->
+    Node;
+maybe_modified_1({value, Node1}, Node, Depth, Message, Notes) ->
+    case Notes of
+	no ->
+	    rewrite(Node, Node1);
+	_ ->
+	    Code = erl_syntax:comment_text(
+		     erl_syntax_lib:to_comment(
+		       erl_syntax_lib:strip_comments(
+			 erl_syntax_lib:limit(Node, Depth)),
+		       "\040\040")),
+	    erl_syntax:add_precomments(
+	      [comment_note(Message ++
+			    ["Original code:" | Code])],
+	      rewrite(Node, Node1))
+    end.
+
+
+%% =====================================================================
+%% @spec create_stubs(Stubs::[stubDescriptor()], Options::[term()]) ->
+%%           [string()]
+%%
+%% @doc Creates stub module source files corresponding to the given stub
+%% descriptors. The returned value is the list of names of the created
+%% files. See `merge_sources/3' for more information about
+%% stub descriptors.
+%%
+%% Options:
+%% <dl>
+%%   <dt>`{backup_suffix, string()}'</dt>
+%%   <dt>`{backups, bool()}'</dt>
+%%   <dt>`{printer, Function}'</dt>
+%%   <dt>`{stub_dir, filename()}'</dt>
+%%   <dt>`{suffix, string()}'</dt>
+%%   <dt>`{verbose, bool()}'</dt>
+%% </dl>
+%% 
+%% See `merge/3' for details on these options.
+%%
+%% @see merge/3
+%% @see merge_sources/3
+
+create_stubs(Stubs, Opts) ->
+    Opts1 = Opts ++ ?DEFAULT_MERGE_OPTS,
+    lists:foldl(fun (S, Fs) ->
+			F = create_stub(S, Opts1),
+			[F | Fs]
+		end,
+		[], Stubs).
+
+maybe_create_stubs(Stubs, Opts) ->
+    case proplists:get_bool(stubs, Opts) of
+	true ->
+	    create_stubs(Stubs, Opts);
+	false ->
+	    []
+    end.
+
+create_stub({Name, Fs, Attrs}, Opts) ->
+    Defs = [stub_function(F) || F <- Fs],
+    Exports = [F || {F, _} <- Fs],
+    Forms = stub_header(Name, Exports, Attrs) ++ Defs,
+    Dir = proplists:get_value(stub_dir, Opts, ""),
+    verbose("creating stub file for module `~w'.", [Name], Opts),
+    write_module(erl_syntax:form_list(Forms), Name, Dir, Opts).
+
+%% We just follow the arity specifications naively when we create the
+%% stub funcion - it is not our responsibility to check them.
+
+stub_function({{F, A}, {M, {F1, A1}}}) ->
+    Vs = var_list(A),
+    Vs1 = var_list(A1),
+    R = erl_syntax:module_qualifier(erl_syntax:atom(M),
+				    erl_syntax:atom(F1)),
+    Call = erl_syntax:application(R, Vs1),
+    erl_syntax:function(erl_syntax:atom(F),
+			[erl_syntax:clause(Vs, [], [Call])]).
+
+var_list(N) ->
+    var_list(N, 1).
+
+var_list(N, I) when N > 0 ->
+    [erl_syntax:variable("X" ++ integer_to_list(I))
+     | var_list(N - 1, I + 1)];
+var_list(0, _) ->
+    [].
+
+stub_header(Name, Exports, Attrs) ->
+    [comment([?COMMENT_BAR,
+	      io_lib:fwrite("This is an automatically "
+			    "generated stub interface\n"
+			    "for the module `~w'.",
+			    [Name]),
+	      "",
+	      timestamp(),
+	      ""]),
+     erl_syntax:attribute(erl_syntax:atom('module'),
+			  [erl_syntax:atom(Name)]),
+     make_export(Exports)]
+	++ make_attributes(Attrs).
+
+
+%% =====================================================================
+%% @spec rename(Files::[filename()], Renamings) -> [string()]
+%% @equiv rename(Files, Renamings, [])
+
+rename(Files, Renamings) ->
+    rename(Files, Renamings, []).
+
+%% =====================================================================
+%% @spec rename(Files::[filename()], Renamings, Options::[term()]) ->
+%%           [string()]
+%%
+%%     Renamings = [{atom(), atom()}]
+%%
+%% @doc Renames a set of possibly interdependent source code modules.
+%% `Files' is a list of file names of source modules to be
+%% processed. `Renamings' is a list of pairs of <em>module
+%% names</em>, representing a mapping from old names to new. The
+%% returned value is the list of output file names.
+%%
+%% Each file in the list will be read and processed separately. For
+%% every file, each reference to some module M, such that there is an
+%% entry `{<em>M</em>, <em>M1</em>}' in
+%% `Renamings', will be changed to the corresponding M1.
+%% Furthermore, if a file F defines module M, and there is an entry
+%% `{<em>M</em>, <em>M1</em>}' in `Renamings', a
+%% new file named `<em>M1</em>.erl' will be created in the
+%% same directory as F, containing the source code for module M, renamed
+%% to M1. If M does not have an entry in `Renamings', the
+%% module is not renamed, only updated, and the resulting source code is
+%% written to `<em>M</em>.erl' (typically, this overwrites
+%% the original file). The `suffix' option (see below) can be
+%% used to change the default "`.erl'" suffix for the
+%% generated files.
+%%
+%% Stub modules will automatically be created (see the
+%% `stubs' and `stub_dir' options below) for each
+%% module that is renamed. These can be used to redirect any calls still
+%% using the old module names. The stub files are created in the same
+%% directory as the source file (typically overwriting the original
+%% file).
+%%
+%% Options:
+%% <dl>
+%%   <dt>`{backup_suffix, string()}'</dt>
+%%   <dt>`{backups, bool()}'</dt>
+%%   <dt>`{printer, Function}'</dt>
+%%   <dt>`{stubs, bool()}'</dt>
+%%   <dt>`{suffix, string()}'</dt>
+%% </dl>
+%% See `merge/3' for details on these options.
+%%
+%% <dl>
+%%   <dt>`{comments, bool()}'</dt>
+%%   <dt>`{preprocess, bool()}'</dt>
+%% </dl>
+%% See `merge_files/4' for details on these options.
+%%
+%% <dl>
+%%   <dt>`{no_banner, bool()}'</dt>
+%% </dl>
+%% For the `rename' function, this option is
+%% `true' by default. See `merge_sources/3' for
+%% details.
+%%
+%% <dl>
+%%   <dt>`{tidy, bool()}'</dt>
+%% </dl>
+%% For the `rename' function, this option is
+%% `false' by default. See `merge_sources/3' for
+%% details.
+%%
+%% <dl>
+%%   <dt>`{no_headers, bool()}'</dt>
+%%   <dt>`{stub_dir, filename()}'</dt>
+%% </dl>
+%% These options are preset by the `rename' function and
+%% cannot be overridden by the user.
+%%
+%% See `merge_sources/3' for further options.
+%%
+%% @see merge/3
+%% @see merge_sources/3
+%% @see merge_files/4
+
+rename(Files, Renamings, Opts) ->
+    Dict = case is_atom_map(Renamings) of
+	       true ->
+		   dict:from_list(Renamings);
+	       false ->
+		   report_error("bad module renaming: ~P.",
+				[Renamings, 10]),
+		   exit(error)
+	   end,
+    %% We disable *all* automatic source code lookup, for safety: you
+    %% are only allowed to do renaming on a module if you give its path.
+    Opts1 = [{find_src_rules, []}]
+	++ Opts ++ [{backup_suffix, ?DEFAULT_BACKUP_SUFFIX},
+		    backups, 
+		    {printer, fun default_printer/2},
+		    stubs,
+		    {suffix, ?DEFAULT_SUFFIX},
+		    comments, 
+		    {preprocess, false},
+		    {tidy, false},
+		    no_banner,
+		    {notes, no},
+		    {verbose, false}],
+    lists:flatmap(fun (F) -> rename_file(F, Dict, Opts1) end, Files).
+
+rename_file(File, Dict, Opts) ->
+    S = read_module(File, Opts),
+    M = get_module_info(S),
+    Name = M#module.name,
+    Name1 = case dict:find(Name, Dict) of
+		{ok, N} -> N;
+		error -> Name
+	    end,
+    %% We convert the dictionary to a new list to ensure that we use the
+    %% exact same renaming for redirections. We must remove the current
+    %% module from the redirection set.
+    Dict1 = dict:erase(Name, Dict),
+    Opts1 = [no_headers,
+	     {export, [Name]},
+	     {static, [Name]},
+	     {redirect, dict:to_list(Dict1)}] ++ Opts,
+    {Tree, Stubs} = merge_sources(Name1, [S], Opts1),
+    Dir = filename:dirname(filename(File)),
+    File1 = write_module(Tree, Name1, Dir, Opts),
+
+    %% We create the stub file in the same directory as the source file
+    %% and the target file.
+    [File1 | maybe_create_stubs(Stubs, [{stub_dir, Dir} | Opts1])].
+
+
+%% ---------------------------------------------------------------------
+%% Initialise a module-info record with data about the module
+%% represented by the syntax tree (or list of "forms"). Listed exports
+%% are guaranteed to be in the set of function names.
+
+get_module_info(Forms) ->
+    L = case catch {ok, erl_syntax_lib:analyze_forms(Forms)} of
+	    {ok, L1} ->
+		L1;
+	    syntax_error ->
+		report_error("syntax error in input."),
+		erlang:error(badarg);
+	    {'EXIT', R} ->
+		exit(R);
+	    R ->
+		throw(R)
+	end,
+    {Name, Vars} =
+	case lists:keyfind(module, 1, L) of
+	    {module, {_N, _Vs} = NVs} ->
+		NVs;
+	    {module, N} ->
+		{N, none};
+	    false ->
+		report_error("in source code: module name missing."),
+		exit(error)
+	end,
+    case lists:keyfind(errors, 1, L) of
+	{errors, Ds} when Ds =/= [] ->
+	    report_errors(Ds, Name),
+	    exit(error);
+	_ ->
+	    ok
+    end,
+    case lists:keyfind(warnings, 1, L) of
+	{warnings, Ds1} when Ds1 =/= [] ->
+	    report_warnings(Ds1, Name); 
+	_ ->
+	    ok
+    end,
+    Functions = case lists:keyfind(functions, 1, L) of
+		    {functions, Fs} ->
+			ordsets:from_list(Fs);
+		    _ ->
+			[]
+		end,
+    Exports = case lists:keyfind(exports, 1, L) of
+		  {exports, Es} ->
+		      ordsets:from_list(Es);
+		  _ ->
+		      []
+	      end,
+    Imports = case lists:keyfind(imports, 1, L) of
+		  {imports, Is} ->
+		      expand_imports(Is, Name);
+		  _ ->
+		      []
+	      end,
+    Attributes = case lists:keyfind(attributes, 1, L) of
+		     {attributes, As} ->
+			 ordsets:from_list(As);
+		     _ ->
+			 []
+		 end,
+    Records = case lists:keyfind(records, 1, L) of
+		  {records, Rs} ->
+		      fold_record_fields(Rs);
+		  _ ->
+		      []
+	      end,
+    check_records(Records, Name),
+    #module{name = Name,
+	    vars = Vars,
+	    functions = Functions,
+	    exports = ordsets:intersection(Exports, Functions),
+	    aliases = Imports,
+	    attributes = Attributes,
+	    records = Records}.
+
+fold_record_fields(Rs) ->
+    [{N, [fold_record_field(F) || F <- Fs]} || {N, Fs} <- Rs].
+
+fold_record_field({_Name, none} = None) ->
+    None;
+fold_record_field({Name, F}) ->
+    case erl_syntax:is_literal(F) of
+	true ->
+	    {Name, {value, erl_syntax:concrete(F)}};
+	false ->
+	    %% The default value for the field is not a constant, so we
+	    %% represent it by a hash value instead. (We don't want to
+	    %% do this in the general case.)
+	    {Name, {hash, erlang:phash(F, 16#ffffff)}}
+    end.
+
+report_errors([D | Ds], Name) ->
+    report_error("error: " ++ error_text(D, Name)),
+    report_errors(Ds, Name);
+report_errors([], _) ->
+    ok.
+
+report_warnings([D | Ds], Name) ->
+    report_warning(error_text(D, Name)),
+    report_errors(Ds, Name);
+report_warnings([], _) ->
+    ok.
+
+error_text(D, Name) ->
+    case D of
+	{L, M, E} when is_integer(L), is_atom(M) ->
+	    case catch M:format_error(E) of
+		S when is_list(S) ->
+		    io_lib:fwrite("`~w', line ~w: ~s.",
+				  [Name, L, S]);
+		_ ->
+		    error_text_1(D, Name)
+	    end;
+	_E ->
+	    error_text_1(D, Name)
+    end.
+
+error_text_1(D, Name) ->
+    io_lib:fwrite("error: `~w', ~P.", [Name, D, 15]).
+
+check_records(Rs, Name) ->
+    case duplicates([N || {N, _} <- Rs]) of
+	[] ->
+	    ok;
+	Ns ->
+	    report_error("in module `~w': "
+			 "multiply defined records: ~p.",
+			 [Name, Ns]),
+	    exit(error)
+    end.
+
+expand_imports(Is, Name) ->
+    Fs = ordsets:from_list(lists:append([[{M, F} || F <- Fs]
+					 || {M, Fs} <- Is])),
+    As = erl_syntax_lib:function_name_expansions(Fs),
+    case duplicates([N || {N, _} <- As]) of
+	[] ->
+	    ordsets:from_list(As);
+	Ns ->
+	    report_error("in module `~w': "
+			 "multiply imported functions: ~p.",
+			 [Name, Ns]),
+	    exit(error)
+    end.
+
+
+%% ---------------------------------------------------------------------
+%% File handling
+
+%% open_output_file(filename()) -> filedescriptor()
+
+open_output_file(FName) ->
+    case catch file:open(FName, [write]) of
+	{ok, FD} ->
+	    FD;
+	{error, _} = Error ->
+	    error_open_output(FName),
+	    exit(Error);
+	{'EXIT', R} ->
+	    error_open_output(FName),
+	    exit(R);
+	R ->
+	    error_open_output(FName),
+	    exit(R)
+    end.
+
+%% read_module(Name, Options) -> syntaxTree()
+%%
+%% This also tries to locate the real source file, if "Name" does not
+%% point directly to a particular file.
+
+read_module(Name, Options) ->
+    case file_type(Name) of
+	{value, _} ->
+	    read_module_1(Name, Options);
+	none ->
+	    Rules = proplists:get_value(find_src_rules, Options),
+	    case find_src(Name, Rules) of
+		{error, _} ->
+		    %% It seems that we have no file - go on anyway,
+		    %% just to get a decent error message.
+		    read_module_1(Name, Options);
+		{Name1, _} ->
+		    read_module_1(Name1 ++ ".erl", Options)
+	    end
+    end.
+
+read_module_1(Name, Options) ->
+    verbose("reading module `~s'.", [filename(Name)], Options),
+    Forms = read_module_2(Name, Options),
+    case proplists:get_bool(comments, Options) of
+	false ->
+	    Forms;
+	true ->
+	    Comments = erl_comment_scan:file(Name),
+	    erl_recomment:recomment_forms(Forms, Comments)
+    end.
+
+read_module_2(Name, Options) ->
+    case read_module_3(Name, Options) of
+	{ok, Forms} ->
+	    check_forms(Forms, Name), 
+	    Forms;
+	{error, _} = Error ->
+	    error_read_file(Name),
+	    exit(Error)
+    end.
+
+read_module_3(Name, Options) ->
+    case proplists:get_bool(preprocess, Options) of
+	false ->
+	    epp_dodger:parse_file(Name);
+	true ->
+	    read_module_4(Name, Options)
+    end.
+
+read_module_4(Name, Options) ->
+    Includes = proplists:append_values(includes, Options)
+	++ [filename:dirname(Name) | ?DEFAULT_INCLUDES],
+    Macros = proplists:append_values(macros, Options)
+	++ ?DEFAULT_MACROS,
+    epp:parse_file(Name, Includes, Macros).
+
+check_forms([F | Fs], File) ->
+    case erl_syntax:type(F) of
+	error_marker ->
+	    S = case erl_syntax:error_marker_info(F) of
+		    {_, M, D} ->
+			M:format_error(D);
+		    _ ->
+			"unknown error"
+		end,
+	    report_error("in file `~s' at line ~w:\n  ~s",
+			 [filename(File), erl_syntax:get_pos(F), S]),
+	    exit(error);
+	_ ->
+	    check_forms(Fs, File)
+    end;
+check_forms([], _) ->
+    ok.
+
+find_src(Name, undefined) ->
+    filename:find_src(filename(Name));
+find_src(Name, Rules) ->
+    filename:find_src(filename(Name), Rules).
+
+%% file_type(filename()) -> {value, Type} | none
+
+file_type(Name) ->
+    case catch file:read_file_info(Name) of
+	{ok, Env} ->
+	    {value, Env#file_info.type};
+	{error, enoent} ->
+	    none;
+	{error, _} = Error ->
+	    error_read_file_info(Name),
+	    exit(Error);
+	{'EXIT', R} ->
+	    error_read_file_info(Name),
+	    exit(R);
+	R ->
+	    error_read_file_info(Name),
+	    throw(R)
+    end.
+
+%% Create the target directory and make a backup file if necessary, then
+%% open the file, output the text and close the file safely. Returns the
+%% file name.
+
+write_module(Tree, Name, Dir, Opts) ->
+    Name1 = filename(Name),
+    Dir1 = filename(Dir),
+    Base = if Dir1 =:= "" ->
+		   Name1;
+	      true ->
+		   case file_type(Dir1) of
+		       {value, directory} ->
+			   ok;
+		       {value, _} ->
+			   report_error("`~s' is not a directory.",
+					[Dir1]),
+			   exit(error);
+		       none ->
+			   case file:make_dir(Dir1) of
+			       ok ->
+				   verbose("created directory `~s'.",
+					   [Dir1], Opts),
+				   ok;
+			       E ->
+				   report_error("failed to create "
+						"directory `~s'.",
+						[Dir1]),
+				   exit({make_dir, E})
+			   end
+		   end,
+		   filename:join(Dir1, Name1)
+	   end,
+    Suffix = proplists:get_value(suffix, Opts, ""),
+    File = Base ++ Suffix,
+    case proplists:get_bool(backups, Opts) of
+	true ->
+	    backup_file(File, Opts);
+	false ->
+	    ok
+    end,
+    Printer = proplists:get_value(printer, Opts),
+    FD = open_output_file(File),
+    verbose("writing to file `~s'.", [File], Opts),
+    V = (catch {ok, output(FD, Printer, Tree, Opts)}),
+    ok = file:close(FD),
+    case V of
+	{ok, _} ->
+	    File;
+	{'EXIT', R} ->
+	    error_write_file(File),
+	    exit(R);
+	R ->
+	    error_write_file(File),
+	    throw(R)
+    end.
+
+output(FD, Printer, Tree, Opts) ->
+    io:put_chars(FD, Printer(Tree, Opts)),
+    io:nl(FD).
+
+%% If the file exists, rename it by appending the given suffix to the
+%% file name.
+
+backup_file(Name, Opts) ->
+    case file_type(Name) of
+	{value, regular} ->
+	    backup_file_1(Name, Opts);
+	{value, _} ->
+	    error_backup_file(Name),
+	    exit(error);
+	none ->
+	    ok
+    end.
+
+%% The file should exist and be a regular file here.
+
+backup_file_1(Name, Opts) ->
+    Name1 = filename(Name),
+    Suffix = proplists:get_value(backup_suffix, Opts, ""),
+    Dest = filename:join(filename:dirname(Name1),
+			 filename:basename(Name1) ++ Suffix),
+    case catch file:rename(Name1, Dest) of
+	ok ->
+	    verbose("made backup of file `~s'.", [Name1], Opts);
+	{error, R} ->
+	    error_backup_file(Name1),
+	    exit({error, R});
+	{'EXIT', R} ->
+	    error_backup_file(Name1),
+	    exit(R);
+	R ->
+	    error_backup_file(Name1),
+	    throw(R)
+    end.
+
+
+%% =====================================================================
+%% Utility functions
+
+%% The form sequence returned by 'erl_tidy:module' is flat, even if the
+%% given tree is not.
+
+tidy(Tree, Opts) ->
+    case proplists:get_bool(tidy, Opts) of
+	true ->
+	    verbose("tidying final module.", Opts),
+	    erl_tidy:module(Tree, ?TIDY_OPTS);
+	false ->
+	    Tree
+    end.
+
+make_attributes(As) ->
+    [make_attribute(A) || A <- As].
+
+make_attribute({Name, Term}) ->
+    erl_syntax:attribute(erl_syntax:atom(Name),
+			 [erl_syntax:abstract(Term)]).
+
+is_auto_import({F, A}) ->
+    erl_internal:bif(F, A);
+is_auto_import(_) ->
+    false.
+
+timestamp() ->
+    {{Yr, Mth, Dy}, {Hr, Mt, Sc}} = erlang:localtime(),
+    lists:flatten(io_lib:fwrite("Created by Igor "
+				"~w-~2.2.0w-~2.2.0w, "
+				"~2.2.0w:~2.2.0w:~2.2.0w.",
+				[Yr, Mth, Dy, Hr, Mt, Sc])).
+
+filename([C | T]) when is_integer(C), C > 0, C =< 255 ->
+    [C | filename(T)];
+filename([H|T]) ->
+    filename(H) ++ filename(T);
+filename([]) ->
+    [];
+filename(N) when is_atom(N) ->
+    atom_to_list(N);
+filename(N) ->
+    report_error("bad filename: `~P'.", [N, 25]),
+    exit(error).
+
+duplicates(Xs) ->
+    ordsets:from_list(Xs -- ordsets:from_list(Xs)).
+
+split_list(F, L) ->
+    split_list(L, F, [], []).
+
+split_list([H | T], F, A1, A2) ->
+    case F(H) of
+	true ->
+	    split_list(T, F, [H | A1], A2);
+	false ->
+	    split_list(T, F, A1, [H | A2])
+    end;
+split_list([], _, A1, A2) ->
+    {lists:reverse(A1), lists:reverse(A2)}.
+
+rewrite(Source, Target) ->
+    erl_syntax:copy_attrs(Source, Target).
+
+comment_note([L | Ls]) ->
+    comment([?NOTE_HEADER ++ L | Ls], ?NOTE_PREFIX).
+
+comment(Txt) ->
+    comment(Txt, ?COMMENT_PREFIX).
+
+comment(Txt, Prefix) ->
+    erl_syntax:comment(prefix_lines(split_lines(Txt), Prefix)).
+
+prefix_lines([L | Ls], Prefix) ->
+    [Prefix ++ L | prefix_lines(Ls, Prefix)];
+prefix_lines([], _) ->
+    [].
+
+split_lines(Ls) ->
+    split_lines(Ls, []).
+
+split_lines([L | Ls], Ls1) ->
+    split_lines(Ls, split_lines(L, [], Ls1));
+split_lines([], Ls1) ->
+    lists:reverse(Ls1).
+
+split_lines([$\r, $\n | Cs], Cs1, Ls) ->
+    split_lines_1(Cs, Cs1, Ls);
+split_lines([$\r | Cs], Cs1, Ls) ->
+    split_lines_1(Cs, Cs1, Ls);
+split_lines([$\n | Cs], Cs1, Ls) ->
+    split_lines_1(Cs, Cs1, Ls);
+split_lines([C | Cs], Cs1, Ls) ->
+    split_lines(Cs, [C | Cs1], Ls);
+split_lines([], Cs, Ls) ->
+    [lists:reverse(Cs) | Ls].
+
+split_lines_1(Cs, Cs1, Ls) ->
+    split_lines(Cs, [], [lists:reverse(Cs1) | Ls]).
+
+
+%% =====================================================================
+%% Reporting
+
+warning_unsafe_call(Name, Module, Target) ->
+    report_warning("call to `~w' in module `~w' "
+		   "possibly unsafe in `~s'.", [Name, Module, Target]).
+
+warning_apply_2(Module, Target) ->
+    report_warning("call to `apply/2' in module `~w' "
+		   "possibly unsafe in `~s'.", [Module, Target]).
+
+error_open_output(Name) ->
+    report_error("cannot open file `~s' for output.", [filename(Name)]).
+
+error_read_file(Name) ->
+    report_error("error reading file `~s'.", [filename(Name)]).
+
+error_read_file_info(Name) ->
+    report_error("error getting file info: `~s'.", [filename(Name)]).
+
+error_write_file(Name) ->
+    report_error("error writing to file `~s'.", [filename(Name)]).
+
+error_backup_file(Name) ->
+    report_error("could not create backup of file `~s'.",
+		 [filename(Name)]).
+
+verbose(S, Opts) ->
+    verbose(S, [], Opts).
+
+verbose(S, Vs, Opts) ->
+    case proplists:get_bool(verbose, Opts) of
+	true ->
+	    report(S, Vs);
+	false ->
+	    ok
+    end.
+
+report_error(S) ->
+    report_error(S, []).
+
+report_error(S, Vs) ->
+    report(S, Vs).
+
+report_warning(S) ->
+    report_warning(S, []).
+
+report_warning(S, Vs) ->
+    report("warning: " ++ S, Vs).
+
+% report(S) ->
+%     report(S, []).
+
+report(S, Vs) ->
+    io:fwrite(lists:concat([?MODULE, ": ", S, "\n"]), Vs).
+
diff --git a/lib/syntax_tools/src/prettypr.erl b/lib/syntax_tools/src/prettypr.erl
new file mode 100644
index 0000000000..4dd95a2b08
--- /dev/null
+++ b/lib/syntax_tools/src/prettypr.erl
@@ -0,0 +1,1301 @@
+%% =====================================================================
+%% This library is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU Lesser General Public License as
+%% published by the Free Software Foundation; either version 2 of the
+%% License, or (at your option) any later version.
+%%
+%% This library is distributed in the hope that it will be useful, but
+%% WITHOUT ANY WARRANTY; without even the implied warranty of
+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+%% Lesser General Public License for more details.
+%%
+%% You should have received a copy of the GNU Lesser General Public
+%% License along with this library; if not, write to the Free Software
+%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+%% USA
+%%
+%% $Id$
+%%
+%% @copyright 2000-2006 Richard Carlsson
+%% @author Richard Carlsson <[email protected]>
+%% @end
+%% =====================================================================
+
+%% @doc A generic pretty printer library. This module uses a
+%% strict-style context passing implementation of John Hughes algorithm,
+%% described in "The design of a Pretty-printing Library". The
+%% paragraph-style formatting, empty documents, floating documents, and
+%% null strings are my own additions to the algorithm.
+%%
+%% To get started, you should read about the {@link document()} data
+%% type; the main constructor functions: {@link text/1}, {@link
+%% above/2}, {@link beside/2}, {@link nest/2}, {@link sep/1}, and {@link
+%% par/2}; and the main layout function {@link format/3}.
+%%
+%% If you simply want to format a paragraph of plain text, you probably
+%% want to use the {@link text_par/2} function, as in the following
+%% example:
+%% ```
+%% prettypr:format(prettypr:text_par("Lorem ipsum dolor sit amet"), 20)
+%% '''
+
+%% @TODO can floats be moved in/out of sep:s without too much pain?
+
+-module(prettypr).
+
+-export([above/2, beside/2, best/3, break/1, empty/0, floating/1,
+	 floating/3, follow/2, follow/3, format/1, format/2, format/3,
+	 nest/2, par/1, par/2, sep/1, text/1, null_text/1, text_par/1,
+	 text_par/2]).
+
+%% ---------------------------------------------------------------------
+
+%% XXX: just an approximation
+-type deep_string() :: [char() | [_]].
+
+%% XXX: poor man's document() until recursive data types are supported
+-type doc() :: 'null'
+             | {'text' | 'fit', _}
+             | {'nest' | 'beside' | 'above' | 'union', _, _}
+             | {'sep' | 'float', _, _, _}.
+
+%% Document structures fully implemented and available to the user:
+-record(text,   {s  :: deep_string()}).
+-record(nest,   {n  :: integer(),   d :: doc()}).
+-record(beside, {d1 :: doc(),      d2 :: doc()}).
+-record(above,  {d1 :: doc(),      d2 :: doc()}).
+-record(sep,    {ds :: [doc()], i = 0 :: integer(), p = false :: boolean()}).
+
+%% Document structure which is not clear whether it is fully implemented: 
+-record(float,  {d  :: doc(), h :: integer(), v :: integer()}).
+
+%% Document structures not available to the user:
+-record(union,  {d1 :: doc(), d2 :: doc()}).
+-record(fit,    {d  :: doc()}).
+
+
+%% ---------------------------------------------------------------------
+%% A small warning for hackers: it's fairly easy to break this
+%% thing (in particular, to muck up the complexity) if you don't
+%% understand how it works.
+%% ---------------------------------------------------------------------
+
+
+%% =====================================================================
+%% @type document(). An abstract character-based "document" representing
+%% a number of possible layouts, which can be processed to produce a
+%% single concrete layout. A concrete layout can then be rendered as a
+%% sequence of characters containing linebreaks, which can be passed to
+%% a printer or terminal that uses a fixed-width font.
+%%
+%% For example, a document `sep([text("foo"), text("bar")])' 
+%% represents the two layouts
+%% ```foo bar'''
+%% and
+%% ```foo
+%%    bar'''
+%%
+%% Which layout is chosen depends on the available horizontal space.
+%% When processing a document, the main parameters are the <em>paper
+%% width</em> and the <em>line width</em> (also known as the "ribbon
+%% width"). In the resulting layout, no text should be printed beyond
+%% the paper width (which by default is 80 characters) as long as it can
+%% be avoided, and each single line of text (its indentation not
+%% counted, hence "ribbon") should preferably be no wider than the
+%% specified line width (which by default is 65).
+%%
+%% Documents can be joined into a single new document using the
+%% constructor functions of this module. Note that the new document
+%% often represents a larger number of possible layouts than just the
+%% sum of the components.
+
+-type document() :: 'null' | #text{} | #nest{} | #beside{}
+                  | #above{} | #sep{} | #float{} | #union{} | #fit{}.
+
+%% =====================================================================
+%% @spec text(Characters::string()) -> document()
+%%
+%% @doc Yields a document representing a fixed, unbreakable sequence of
+%% characters. The string should contain only <em>printable</em>
+%% characters (tabs allowed but not recommended), and <em>not</em>
+%% newline, line feed, vertical tab, etc. A tab character (`\t') is
+%% interpreted as padding of 1-8 space characters to the next column of
+%% 8 characters <em>within the string</em>.
+%%
+%% @see empty/0
+%% @see null_text/1
+%% @see text_par/2
+
+-spec text(string()) -> #text{}.
+
+text(S) ->
+    mktext(string(S)).	  % convert to internal representation
+
+%% This function is used internally only, and expects a string on
+%% the internal representation:
+
+mktext(S) ->
+    #text{s = S}.
+
+
+%% =====================================================================
+%% @spec null_text(Characters::string()) -> document()
+%%
+%% @doc Similar to {@link text/1}, but the result is treated as having
+%% zero width. This is regardless of the actual length of the string.
+%% Null text is typically used for markup, which is supposed to have no
+%% effect on the actual layout.
+%%
+%% The standard example is when formatting source code as HTML to be
+%% placed within `<pre>...</pre>' markup, and using e.g. `<i>' and `<b>'
+%% to make parts of the source code stand out. In this case, the markup
+%% does not add to the width of the text when viewed in an HTML browser,
+%% so the layout engine should simply pretend that the markup has zero
+%% width.
+%%
+%% @see text/1
+%% @see empty/0
+
+-spec null_text(string()) -> #text{}.
+
+null_text(S) ->
+    mktext(null_string(S)).    % convert to internal representation
+
+
+%% =====================================================================
+%% @spec text_par(Text::string()) -> document()
+%% @equiv text_par(Text, 0)
+
+-spec text_par(string()) -> document().
+
+text_par(S) ->
+    text_par(S, 0).
+
+
+%% =====================================================================
+%% @spec text_par(Text::string(), Indentation::integer()) -> document()
+%%
+%% @doc Yields a document representing paragraph-formatted plain text.
+%% The optional `Indentation' parameter specifies the extra indentation
+%% of the first line of the paragraph. For example, `text_par("Lorem
+%% ipsum dolor sit amet", N)' could represent
+%% ```Lorem ipsum dolor
+%%    sit amet'''
+%% if `N' = 0, or
+%% ```  Lorem ipsum
+%%    dolor sit amet'''
+%% if `N' = 2, or
+%% ```Lorem ipsum dolor
+%%      sit amet'''
+%% if `N' = -2.
+%% 
+%% (The sign of the indentation is thus reversed compared to the {@link
+%% par/2} function, and the behaviour varies slightly depending on the
+%% sign in order to match the expected layout of a paragraph of text.)
+%%
+%% Note that this is just a utility function, which does all the work of
+%% splitting the given string into words separated by whitespace and
+%% setting up a {@link par/2. `par'} with the proper indentation,
+%% containing a list of {@link text/1. `text'} elements.
+%%
+%% @see text_par/1
+%% @see text/1
+%% @see par/2
+
+-spec text_par(string(), integer()) -> document().
+
+text_par(S, 0) ->
+    par(words(S));
+text_par(S, N) when N > 0 ->
+    nest(N, par(words(S), -N));
+text_par(S, N) when N < 0 ->
+    par(words(S), -N).
+
+words(S) ->
+    words(S, [], []).
+
+words([$\s | Cs], As, Ws) -> words_1(Cs, As, Ws);
+words([$\t | Cs], As, Ws) -> words_1(Cs, As, Ws);
+words([$\n | Cs], As, Ws) -> words_1(Cs, As, Ws);
+words([C | Cs], As, Ws) -> words(Cs, [C | As], Ws);
+words([], [], Ws) -> lists:reverse(Ws);
+words([], As, Ws) -> words_1([], As, Ws).
+
+words_1(Cs, [], Ws) ->
+    words(Cs, [], Ws);
+words_1(Cs, As, Ws) ->
+    words(Cs, [], [text(lists:reverse(As)) | Ws]).
+
+
+%% =====================================================================
+%% @spec empty() -> document()
+%%
+%% @doc Yields the empty document, which has neither height nor width.
+%% (`empty' is thus different from an empty {@link text/1. `text'}
+%% string, which has zero width but height 1.)
+%% 
+%% Empty documents are occasionally useful; in particular, they have the
+%% property that `above(X, empty())' will force a new line after `X'
+%% without leaving an empty line below it; since this is a common idiom,
+%% the utility function {@link break/1} will place a given document in
+%% such a context.
+%%
+%% @see text/1
+
+-spec empty() -> 'null'.
+
+empty() ->
+    null.
+
+
+%% =====================================================================
+%% @spec break(document()) -> document()
+%%
+%% @doc Forces a line break at the end of the given document. This is a
+%% utility function; see {@link empty/0} for details.
+
+-spec break(document()) -> #above{}.
+
+break(D) ->
+    above(D, empty()).
+
+
+%% =====================================================================
+%% @spec nest(N::integer(), D::document()) -> document()
+%%
+%% @doc Indents a document a number of character positions to the right.
+%% Note that `N' may be negative, shifting the text to the left, or
+%% zero, in which case `D' is returned unchanged.
+
+-spec nest(integer(), document()) -> document().
+
+nest(N, D) ->
+    if N =:= 0 ->
+	    D;
+       true ->
+	    #nest{n = N, d = D}
+    end.
+
+
+%% =====================================================================
+%% @spec beside(D1::document(), D2::document()) -> document()
+%%
+%% @doc Concatenates documents horizontally. Returns a document
+%% representing the concatenation of the documents `D1' and `D2' such
+%% that the last character of `D1' is horizontally adjacent to the first
+%% character of `D2', in all possible layouts. (Note: any indentation of
+%% `D2' is lost.)
+%%
+%% Examples:
+%% ```ab  cd  =>  abcd
+%%
+%%    ab  ef      ab
+%%    cd  gh  =>  cdef
+%%                  gh'''
+
+-spec beside(document(), document()) -> #beside{}.
+
+beside(D1, D2) ->
+    #beside{d1 = D1, d2 = D2}.
+
+
+%% =====================================================================
+%% @spec above(D1::document(), D2::document()) -> document()
+%%
+%% @doc Concatenates documents vertically. Returns a document
+%% representing the concatenation of the documents `D1' and `D2' such
+%% that the first line of `D2' follows directly below the last line of
+%% `D1', and the first character of `D2' is in the same horizontal
+%% column as the first character of `D1', in all possible layouts.
+%%
+%% Examples:
+%% ```ab  cd  =>  ab
+%%                cd
+%%
+%%                   abc
+%%    abc   fgh  =>   de
+%%     de    ij      fgh
+%%                    ij'''
+
+-spec above(document(), document()) -> #above{}.
+
+above(D1, D2) ->
+    #above{d1 = D1, d2 = D2}.
+
+
+%% =====================================================================
+%% @spec sep(Docs::[document()]) -> document()
+%%
+%% @doc Arranges documents horizontally or vertically, separated by
+%% whitespace. Returns a document representing two alternative layouts
+%% of the (nonempty) sequence `Docs' of documents, such that either all
+%% elements in `Docs' are concatenated horizontally, and separated by a
+%% space character, or all elements are concatenated vertically (without
+%% extra separation).
+%%
+%% Note: If some document in `Docs' contains a line break, the vertical
+%% layout will always be selected.
+%%
+%% Examples:
+%% ```                             ab
+%%    ab  cd  ef  =>  ab cd ef  |  cd
+%%                                 ef
+%%
+%%    ab           ab
+%%    cd  ef  =>   cd
+%%                 ef'''
+%%
+%% @see par/2
+
+-spec sep([document()]) -> #sep{}.
+
+sep(Ds) ->
+    #sep{ds = Ds}.
+
+
+%% =====================================================================
+%% @spec par(Docs::[document()]) -> document()
+%% @equiv par(Ds, 0)
+
+-spec par([document()]) -> #sep{}.
+
+par(Ds) ->
+    par(Ds, 0).
+
+
+%% =====================================================================
+%% @spec par(Docs::[document()], Offset::integer()) -> document()
+%%
+%% @doc Arranges documents in a paragraph-like layout. Returns a
+%% document representing all possible left-aligned paragraph-like
+%% layouts of the (nonempty) sequence `Docs' of documents. Elements in
+%% `Docs' are separated horizontally by a single space character and
+%% vertically with a single line break. All lines following the first
+%% (if any) are indented to the same left column, whose indentation is
+%% specified by the optional `Offset' parameter relative to the position
+%% of the first element in `Docs'. For example, with an offset of -4,
+%% the following layout can be produced, for a list of documents
+%% representing the numbers 0 to 15:
+%%
+%% ```    0 1 2 3
+%%    4 5 6 7 8 9
+%%    10 11 12 13
+%%    14 15'''
+%% or with an offset of +2:
+%% ```0 1 2 3 4 5 6
+%%      7 8 9 10 11
+%%      12 13 14 15'''
+%%
+%% The utility function {@link text_par/2} can be used to easily
+%% transform a string of text into a `par' representation by splitting
+%% it into words.
+%%
+%% Note that whenever a document in `Docs' contains a line break, it
+%% will be placed on a separate line. Thus, neither a layout such as
+%% ```ab cd
+%%       ef'''
+%% nor
+%% ```ab
+%%    cd ef'''
+%% will be generated. However, a useful idiom for making the former
+%% variant possible (when wanted) is `beside(par([D1, text("")], N),
+%% D2)' for two documents `D1' and `D2'. This will break the line
+%% between `D1' and `D2' if `D1' contains a line break (or if otherwise
+%% necessary), and optionally further indent `D2' by `N' character
+%% positions. The utility function {@link follow/3} creates this context
+%% for two documents `D1' and `D2', and an optional integer `N'.
+%%
+%% @see par/1
+%% @see text_par/2
+
+-spec par([document()], integer()) -> #sep{}.
+
+par(Ds, N) ->
+    mksep(Ds, N, true).
+
+%% Used internally only:
+
+mksep(Ds, N, P) when is_integer(N) ->
+    #sep{ds = Ds, i = N, p = P}.
+
+
+%% =====================================================================
+%% @spec follow(D1::document(), D2::document()) -> document()
+%% @equiv follow(D1, D2, 0)
+
+-spec follow(document(), document()) -> #beside{}.
+
+follow(D1, D2) ->
+    follow(D1, D2, 0).
+
+
+%% =====================================================================
+%% @spec follow(D1::document(), D2::document(), Offset::integer()) ->
+%%           document()
+%% 
+%% @doc Separates two documents by either a single space, or a line
+%% break and intentation. In other words, one of the layouts
+%% ```abc def'''
+%% or
+%% ```abc
+%%     def'''
+%% will be generated, using the optional offset in the latter case. This
+%% is often useful for typesetting programming language constructs.
+%%
+%% This is a utility function; see {@link par/2} for further details.
+%%
+%% @see follow/2
+
+-spec follow(document(), document(), integer()) -> #beside{}.
+
+follow(D1, D2, N) when is_integer(N) ->
+    beside(par([D1, nil()], N), D2).
+
+
+%% =====================================================================
+%% @spec floating(document()) -> document()
+%% @equiv floating(D, 0, 0)
+
+-spec floating(document()) -> #float{}.
+
+floating(D) ->
+    floating(D, 0, 0).
+
+
+%% =====================================================================
+%% @spec floating(D::document(), Hp::integer(), Vp::integer()) ->
+%%           document()
+%%
+%% @doc Creates a "floating" document. The result represents the same
+%% set of layouts as `D'; however, a floating document may be moved
+%% relative to other floating documents immediately beside or above it,
+%% according to their relative horizontal and vertical priorities. These
+%% priorities are set with the `Hp' and `Vp' parameters; if omitted,
+%% both default to zero.
+%%
+%% Notes: Floating documents appear to work well, but are currently less
+%% general than you might wish, losing effect when embedded in certain
+%% contexts. It is possible to nest floating-operators (even with
+%% different priorities), but the effects may be difficult to predict.
+%% In any case, note that the way the algorithm reorders floating
+%% documents amounts to a "bubblesort", so don't expect it to be able to
+%% sort large sequences of floating documents quickly.
+
+-spec floating(document(), integer(), integer()) -> #float{}.
+
+floating(D, H, V) when is_integer(H), is_integer(V) ->
+    #float{d = D, h = H, v = V}.
+
+
+%% =====================================================================
+%% @spec format(D::document()) -> string()
+%% @equiv format(D, 80)
+
+-spec format(document()) -> string().
+
+format(D) ->
+    format(D, 80).
+
+
+%% =====================================================================
+%% @spec format(D::document(), PaperWidth::integer()) -> string()
+%% @equiv format(D, PaperWidth, 65)
+
+-spec format(document(), integer()) -> string().
+
+format(D, W) ->
+    format(D, W, 65).
+
+
+%% =====================================================================
+%% @spec format(D:: document(), PaperWidth::integer(),
+%%              LineWidth::integer()) -> string()
+%% @throws no_layout
+%%
+%% @doc Computes a layout for a document and returns the corresponding
+%% text. See {@link document()} for further information. Throws
+%% `no_layout' if no layout could be selected.
+%%
+%% `PaperWidth' specifies the total width (in character positions) of
+%% the field for which the text is to be laid out. `LineWidth' specifies
+%% the desired maximum width (in number of characters) of the text
+%% printed on any single line, disregarding leading and trailing white
+%% space. These parameters need to be properly balanced in order to
+%% produce good layouts. By default, `PaperWidth' is 80 and `LineWidth'
+%% is 65.
+%%
+%% @see best/3
+
+-spec format(document(), integer(), integer()) -> string().
+
+format(D, W, R) ->
+    case best(D, W, R) of
+	empty ->
+	    throw(no_layout);
+	L -> layout(L)
+    end.
+
+
+%% =====================================================================
+%% Representation:
+%%
+%%	document() = #text{s = string()}
+%%		   | #nest{n = integer(), d = document()}
+%%		   | #beside{d1 = document(), d2 = document()}
+%%		   | #above{d1 = document(), d2 = document()}
+%%		   | #sep{ds = [document()], i = integer(), p = boolean()}
+%%		   | null
+%%
+%% A `text' node simply represents a string (which should not contain
+%% linefeed or carriage return characters). A `nest' node specifies a
+%% relative indentation (in number of character positions) of a
+%% document. The indentation could be a negative number. A `beside' node
+%% specifies a horizontal composition of two documents, and an `above'
+%% node a vertical composition. A `sep' node specifies a list of
+%% alternative documents; the `i' field holds the extra indentation of
+%% all documents but the first in `ds', and if the `p' field is `true'
+%% then the list is typeset in paragraph mode.
+%%
+%% The function `best/3' yields a representation of a "best layout",
+%% suitable for direct conversion to text, having the following
+%% restricted form:
+%%
+%%	layout() = #text{s = string()}
+%%		 | #above{d1 = #text{s = string()}, d2 = layout()}
+%%		 | #nest{n = integer(), d = layout()}
+%%		 | null
+%%
+%% The function `layout/1' performs the final transformation to a single
+%% flat string from the restricted document form.
+
+layout(L) ->
+    lists:reverse(layout(0, L, [])).
+
+layout(N, #above{d1 = #text{s = S}, d2 = L}, Cs) ->
+    layout(N, L, [$\n | flatrev(string_chars(S), indent(N, Cs))]);
+layout(N, #nest{n = N1, d = L}, Cs) ->
+    layout(N + N1, L, Cs);
+layout(N, #text{s = S}, Cs) ->
+    flatrev(string_chars(S), indent(N, Cs));
+layout(_N, null, Cs) ->
+    Cs.
+
+indent(N, Cs) when N >= 8 ->
+    indent(N - 8, [$\t | Cs]);
+indent(N, Cs) when N > 0 ->
+    indent(N - 1, [$\s | Cs]);
+indent(_N, Cs) ->
+    Cs.
+
+flatrev(Cs, As) ->
+    flatrev(Cs, As, []).
+
+flatrev([C = [_|_] | Cs], As, Ss) ->
+    flatrev(C, As, [Cs | Ss]);
+flatrev([[] | Cs], As, Ss) ->
+    flatrev(Cs, As, Ss);
+flatrev([C | Cs], As, Ss) ->
+    flatrev(Cs, [C | As], Ss);
+flatrev([], As, [S | Ss]) ->
+    flatrev(S, As, Ss);
+flatrev([], As, []) ->
+    As.
+
+
+%% =====================================================================
+%% @spec best(document(), PaperWidth::integer(),
+%%            LineWidth::integer()) -> empty | document()
+%%
+%% @doc Selects a "best" layout for a document, creating a corresponding
+%% fixed-layout document. If no layout could be produced, the atom
+%% `empty' is returned instead. For details about `PaperWidth' and
+%% `LineWidth', see {@link format/3}. The function is idempotent.
+%%
+%% One possible use of this function is to compute a fixed layout for a
+%% document, which can then be included as part of a larger document.
+%% For example:
+%% ```above(text("Example:"), nest(8, best(D, W - 12, L - 6)))'''
+%% will format `D' as a displayed-text example indented by 8, whose
+%% right margin is indented by 4 relative to the paper width `W' of the
+%% surrounding document, and whose maximum individual line length is
+%% shorter by 6 than the line length `L' of the surrounding document.
+%%
+% This function is used by the {@link format/3} function to prepare a
+%% document before being laid out as text.
+
+%% Recall that a document represents a set of possible layouts. `best'
+%% selects the "best" layout of a document, returning a simplified
+%% representation that can be given directly to `layout', unless the
+%% returned value is `empty', signaling that no layout could be
+%% produced. In addition, documents on the form `#union{d1 = D1, d2 =
+%% D2}' and `#fit{d = D}' are used internally.
+%%
+%% Note: It is vital for this algorithm to maintain the invariant on
+%% unions that the left argument has a longer first line than the right
+%% argument!
+
+%% Contexts:
+%%
+%%	#c_best_nest{w = integer(), r = integer(), i = integer()}
+%%	#c_above_nest{d = doc(), i = integer(), c = ctxt()}
+%%	#c_beside{d = doc(), c = ctxt()}
+%%	#c_text_beside{s = string(), c = ctxt()}
+%%	#c_sep_nest{ds = [doc()], i = integer(), p = boolean(),
+%%		    c = ctxt()}
+%%	#c_best_nest_or{w = integer(), r = integer(), i = integer(),
+%%			d = doc()}
+%%	#c_fit{c = ctxt()}
+
+-record(c_best_nest, {w, r, i}).	%% best(w, r, nest(i, *))
+
+-record(c_above_nest, {d, i = 0, c}).	%% above(*, nest(i, d))
+
+-record(c_beside, {d, c}).		%% beside(*, d)
+
+-record(c_text_beside, {s, c}).		%% beside(text(s), *)
+
+%% p = false	=>	sep([* | map(nest i, ds)])
+%% p = true	=>	par([* | map(nest i, ds)])
+
+-record(c_sep_nest, {ds, i, p, c}).
+
+-record(c_best_nest_or, {w, r, i, d}).	%% nicest(
+					%%   best(w, r,
+					%%	  nest(i, *)),
+					%%   best(w, r, d))
+
+-record(c_fit, {c}).			%% fit(*)
+
+-record(c_float_beside, {d, h, v, c}).		%% beside(
+						%%   float(d, h,
+						%%         v),
+						%%   *)
+-record(c_float_above_nest, {d, h, v, i, c}).	%% above(
+						%%   float(d, h,
+						%%         v),
+						%%   nest(i, *))
+
+%% Contexts introduced:		In case:
+%%
+%%	c_best_nest		top-level call
+%%	c_above_nest		above (c_best_nest)
+%%	c_beside		beside (c_best_nest)
+%%	c_text_beside		text (c_beside)
+%%	c_sep_nest		sep (c_best_nest)
+%%	c_best_nest_or		union (c_best_nest)
+%%	c_fit			fit
+%%	c_float_beside		float (c_beside)
+%%	c_float_above_nest	float (c_above_nest)
+
+%% Entry point for the layout algorithm:
+
+-spec best(document(), integer(), integer()) -> 'empty' | document().
+
+best(D, W, R) ->
+    rewrite(D, #c_best_nest{w = W, r = R, i = 0}).
+
+rewrite(#text{s = S}, C) ->
+    case C of
+	#c_best_nest{i = N} ->
+	    nest(N, mktext(S));		% finish
+	#c_above_nest{d = D1, i = N1, c = C1} ->
+	    case C1 of
+		#c_best_nest{w = W, r = R, i = N} ->
+		    %% Move out completed line.
+		    %% (Note new indentation N1.)
+		    nest(N,
+			 above(mktext(S),
+			       rewrite(D1,
+				       #c_best_nest{w = W - N,
+						    r = R,
+						    i = N1})));
+		#c_beside{d = D2, c = C2} ->
+		    %% Associativity (not symmetric)
+		    rewrite(above(mktext(S),
+				  nest(N1, beside(D1, D2))), C2);
+		#c_text_beside{s = S1, c = C2} ->
+		    %% Join segments (note the indentation!)
+		    rewrite(above(mktext(concat(S1, S)),
+				  nest(N1 + width(S1), D1)),
+			    C2);
+		#c_sep_nest{ds = Ds, i = N, c = C2} ->
+		    case is_empty_string(S) of
+			false ->
+			    %% Move out the prefix (note the
+			    %% indentation!)
+			    W = width(S),
+			    rewrite(beside(
+				      mktext(S),
+				      mksep([above(nil(),
+						   nest(N1 - W,
+							D1))
+					     | Ds],
+					    N - W,
+					    C1#c_sep_nest.p)),
+				    C2);
+			true ->
+			    %% Like when we have just an empty
+			    %% string and nothing else, this
+			    %% forces us to expand the `sep'. The
+			    %% line break will then force a normal
+			    %% `sep' to select the vertical
+			    %% alternative, but for a `par', we
+			    %% need to force a line break before
+			    %% the remaining elements are laid
+			    %% out. (Note the indentation!)
+			    case C1#c_sep_nest.p of
+				false ->
+				    rewrite(expand_sep(
+					      above(nil(),
+						    nest(N1, D1)),
+					      Ds, N),
+					    C2);
+				true ->
+				    rewrite(expand_par(
+					      above(nil(),
+						    nest(N1, D1)),
+					      Ds, N),
+					    C2)
+			    end
+		    end;
+		#c_best_nest_or{w = W, r = R, i = N, d = D} ->
+		    L = width(S),
+		    case ((L + N) > W) or (L > R) of
+			true ->
+			    %% The first line of the LHS layout is
+			    %% not nice, so select the RHS.
+			    rewrite(D, #c_best_nest{w = W, r = R,
+						    i = N});
+			false ->
+			    %% Select the LHS. (Note the
+			    %% indentation!)
+			    rewrite(above(mktext(S),
+					  nest(N1, D1)),
+				    #c_best_nest{w = W, r = R,
+						 i = N})
+		    end;
+		#c_float_beside{d = D2, c = C2} ->
+		    rewrite(beside(D2, above(mktext(S),
+					     nest(N1, D1))),
+			    C2);
+		#c_float_above_nest{d = D2, i = N2, c = C2} ->
+		    rewrite(above(D2,
+				  nest(N2, above(mktext(S),
+						 nest(N1, D1)))),
+			    C2);
+		#c_above_nest{} ->
+		    exit(badarg);	% this can't happen
+		#c_fit{} ->
+		    exit(badarg)	% this can't happen
+	    end;
+	#c_beside{d = D1, c = C1} ->
+	    case C1 of
+		#c_above_nest{d = D2, i = N, c = C2} ->
+		    case is_empty_string(S) of
+			false ->
+			    %% Move out the prefix (note the
+			    %% indentation!)
+			    W = width(S),
+			    rewrite(beside(mktext(S),
+					   above(
+					     beside(nil(), D1),
+					     nest(N - W, D2))),
+				    C2);
+			true ->
+			    %% Pass on
+			    rewrite(D1, #c_text_beside{s = S,
+						       c = C1})
+		    end;
+		#c_text_beside{s = S1, c = C2} ->
+		    %% Associativity (we simplify early)
+		    rewrite(beside(mktext(concat(S1, S)), D1),
+			    C2);
+		#c_sep_nest{ds = Ds, i = N, c = C2} ->
+		    case is_empty_string(S) of
+			false ->
+			    %% Move out the prefix (note the
+			    %% indentation!)
+			    W = width(S),
+			    rewrite(beside(mktext(S),
+					   mksep(
+					     [beside(nil(), D1)
+					      | Ds],
+					     N - W,
+					     C1#c_sep_nest.p)),
+				    C2);
+			true ->
+			    %% Pass on
+			    rewrite(D1, #c_text_beside{s = S,
+						       c = C1})
+		    end;
+		#c_best_nest_or{w = W, r = R, i = N, d = D} ->
+		    L = width(S),
+		    case ((L + N) > W) or (L > R) of
+			true ->
+			    %% The first line of the LHS layout is
+			    %% not nice, so select the RHS.
+			    rewrite(D, #c_best_nest{w = W, r = R,
+						    i = N});
+			false ->
+			    %% Pass on
+			    rewrite(D1, #c_text_beside{s = S,
+						       c = C1})
+		    end;
+		#c_float_beside{d = D2, c = C2} ->
+		    rewrite(beside(D2, beside(mktext(S), D1)),
+			    C2);
+		#c_float_above_nest{d = D2, i = N, c = C2} ->
+		    rewrite(above(D2,
+				  nest(N, beside(mktext(S), D1))),
+			    C2);
+		_ ->
+		    %% Pass on
+		    rewrite(D1, #c_text_beside{s = S, c = C1})
+	    end;
+	#c_text_beside{s = S1, c = C1} ->
+	    rewrite(mktext(concat(S1, S)), C1);	% join segments
+	#c_sep_nest{ds = Ds, i = N, c = C1} ->
+	    case is_empty_string(S) of
+		false ->
+		    %% Move out the prefix (note the indentation!)
+		    rewrite(beside(mktext(S),
+				   mksep([nil() | Ds],
+					 N - width(S),
+					 C#c_sep_nest.p)),
+			    C1);
+		true ->
+		    %% This is the only place where we are forced to
+		    %% introduce a union. Recall the invariant that the
+		    %% left argument must have a longer first line than
+		    %% the right argument; also recall that `Ds' is
+		    %% always nonempty here. Now, since [D | Ds]
+		    %% contains at least two elements, the first line of
+		    %% the horizontal layout will always contain at
+		    %% least one space character more than the first
+		    %% line of the vertical layout.
+		    case C#c_sep_nest.p of
+			false ->
+			    rewrite(expand_sep(nil(), Ds, N), C1);
+			true ->
+			    rewrite(expand_par(nil(), Ds, N), C1)
+		    end
+	    end;
+	#c_best_nest_or{w = W, r = R, i = N, d = D} ->
+	    L = width(S),
+	    case ((L + N) > W) or (L > R) of
+		true ->
+		    %% The first line of the LHS layout is not
+		    %% nice, so select the RHS (which contains
+		    %% at least two lines).
+		    rewrite(D, #c_best_nest{w = W, r = R, i = N});
+		false ->
+		    nest(N, mktext(S))	  % finish
+	    end;
+	#c_fit{c = C1} ->
+	    %% Identity:
+	    rewrite(mktext(S), C1);
+	#c_float_beside{d = D1, c = C1} ->
+	    rewrite(beside(D1, mktext(S)), C1);
+	#c_float_above_nest{d = D1, i = N, c = C1} ->
+	    rewrite(above(D1, nest(N, mktext(S))), C1)
+    end;
+rewrite(#nest{n = N, d = D}, C) ->
+    case C of
+	#c_best_nest{w = W, r = R, i = N1} ->
+	    %% Note that we simplify by not creating an actual `nest'
+	    %% node, but instead just modifying the context:
+	    %% rewrite(nest(N1, nest(N, D))) = rewrite(nest(N1 + N, D)).
+	    rewrite(D, #c_best_nest{w = W, r = R, i = N + N1});
+	#c_above_nest{d = D1, i = N1, c = C1} ->
+	    %% Distributivity
+	    %% (Note the indentation!)
+	    rewrite(nest(N, above(D, nest(N1 - N, D1))), C1);
+	#c_beside{d = D1, c = C1} ->
+	    %% Associativity (not symmetric):
+	    rewrite(nest(N, beside(D, D1)), C1);
+	#c_text_beside{} ->
+	    rewrite(D, C);   % (`beside' kills RHS indentation)
+	#c_sep_nest{ds = Ds, i = N1, c = C1} ->
+	    %% Distributivity (in the vertical form, the RHS
+	    %% indentation is killed)
+	    rewrite(nest(N, mksep([D | Ds],
+				  N1 - N,
+				  C#c_sep_nest.p)),
+		    C1);
+	#c_fit{c = C1} ->
+	    %% Distributivity:
+	    rewrite(nest(N, fit(D)), C1);
+	#c_float_beside{} ->
+	    rewrite(D, C);    % (`beside' kills RHS indentation)
+	#c_float_above_nest{d = D1, h = H, v = V, i = N1,
+			    c = C1} ->
+	    rewrite(D, #c_float_above_nest{d = D1, h = H, v = V,
+					   i = N + N1, c = C1});
+	#c_best_nest_or{} ->
+	    exit(badarg)    % this can't happen
+    end;
+rewrite(#above{d1 = D1, d2 = D2}, C) ->
+    case C of
+	#c_above_nest{d = D3, i = N, c = C1} ->
+	    %% Associativity:
+	    %% (Note the indentation!)
+	    rewrite(D1, #c_above_nest{d = above(D2, nest(N, D3)),
+				      c = C1});
+	#c_beside{d = D3, c = C1} ->
+	    %% Associativity (not symmetric):
+	    rewrite(above(D1, beside(D2, D3)), C1);
+	#c_fit{c = C1} ->
+	    rewrite(empty, C1);	% this is the whole point of `fit'
+	_ ->
+	    rewrite(D1, #c_above_nest{d = D2, c = C})	% pass on
+    end;
+rewrite(#beside{d1 = D1, d2 = D2}, C) ->
+    case C of
+	#c_beside{d = D3, c = C1} ->
+	    %% Associativity:
+	    rewrite(D1, #c_beside{d = beside(D2, D3), c = C1});
+	#c_fit{c = C1} ->
+	    %% Distributivity:
+	    rewrite(beside(fit(D1), fit(D2)), C1);
+	_ ->
+	    rewrite(D1, #c_beside{d = D2, c = C})	% pass on
+    end;
+rewrite(#sep{ds = Ds, i = N, p = P}, C) ->
+    case C of
+	#c_fit{c = C1} ->
+	    %% The vertical layout is thus impossible, and the
+	    %% extra indentation has no effect.
+	    rewrite(fit(horizontal(Ds)), C1);
+	#c_float_beside{d = D1, c = C1} ->
+	    %% Floats are not moved in or out of sep's
+	    rewrite(beside(D1, mksep(Ds, N, P)), C1);
+	#c_float_above_nest{d = D1, i = N1, c = C1} ->
+	    %% Floats are not moved in or out of sep's
+	    rewrite(above(D1, nest(N1, mksep(Ds, N, P))), C1);
+	_ ->
+	    enter_sep(Ds, N, P, C)		% pass on
+    end;
+rewrite(#union{d1 = D1, d2 = D2}, C) ->
+    %% Introduced by the occurrence of an empty `text' string in a
+    %% `sep' context. See the note above about the invariant for
+    %% unions!
+    case C of
+	#c_best_nest{w = W, r = R, i = N} ->
+	    %% Pass on
+	    rewrite(D1, #c_best_nest_or{w = W, r = R, i = N,
+					d = D2});
+	#c_above_nest{d = D3, i = N, c = C1} ->
+	    %% Distributivity:
+	    %% (Note the indentation!)
+	    rewrite(union(above(D1, nest(N, D3)),
+			  above(D2, nest(N, D3))),
+		    C1);
+	#c_beside{d = D3, c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(beside(D1, D3), beside(D2, D3)), C1);
+	#c_text_beside{s = S, c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(beside(mktext(S), D1),
+			  beside(mktext(S), D2)),
+		    C1);
+	#c_sep_nest{ds = Ds, i = N, c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(mksep([D1 | Ds], N, C#c_sep_nest.p),
+			  mksep([D2 | Ds], N, C#c_sep_nest.p)),
+		    C1);
+	#c_best_nest_or{w = W, r = R, i = N, d = D3} ->
+	    %% Associativity:
+	    rewrite(D1, #c_best_nest_or{w = W, r = R, i = N,
+					d = union(D2, D3)});
+	#c_fit{c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(fit(D1), fit(D2)), C1);
+	#c_float_beside{d = D3, h = H, v = V, c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(beside(floating(D3, H, V), D1),
+			  beside(floating(D3, H, V), D2)),
+		    C1);
+	#c_float_above_nest{d = D3, h = H, v = V, i = N, c = C1} ->
+	    %% Distributivity:
+	    rewrite(union(above(floating(D3, H, V), nest(N, D1)),
+			  above(floating(D3, H, V), nest(N, D2))),
+		    C1)
+    end;
+rewrite(empty, C) ->
+    %% Introduced by `sep'.
+    case C of
+	#c_best_nest{} ->
+	    empty;		% preserve `empty'
+	#c_above_nest{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_beside{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_text_beside{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_sep_nest{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_best_nest_or{w = W, r = R, i = N, d = D} ->
+	    %% Try the other layout
+	    rewrite(D, #c_best_nest{w = W, r = R, i = N});
+	#c_fit{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_float_beside{c = C1} ->
+	    rewrite(empty, C1);	% preserve `empty'
+	#c_float_above_nest{c = C1} ->
+	    rewrite(empty, C1)	% preserve `empty'
+	end;
+rewrite(#fit{d = D}, C) ->
+    %% Introduced by the occurrence of an empty `text' string in a
+    %% `sep' context.
+    case C of
+	#c_fit{} ->
+	    %% Idempotency:
+	    rewrite(D, C);
+	_ ->
+	    rewrite(D, #c_fit{c = C})	% pass on
+    end;
+rewrite(#float{d = D, h = H, v = V}, C) ->
+    case C of
+	#c_beside{d = D1, c = C1} ->
+	    case C1 of
+		#c_float_beside{d = D2, h = H1, v = V1, c = C2}
+		when H1 > H ->
+		    %% Move left
+		    rewrite(beside(floating(D, H, V),
+				   beside(floating(D2, H1, V1),
+					  D1)),
+			    C2);
+		#c_float_beside{d = D2, h = H1, v = V1, c = C2}
+		when V1 /= V ->
+		    %% Align vertically
+		    rewrite(above(floating(D2, H1, V1),
+				  beside(floating(D, H, V), D1)),
+			    C2);
+		#c_float_above_nest{d = D2, h = H1, v = V1,
+				    i = N1, c = C2}
+		when V1 > V ->
+		    %% Move up (note the indentation, and note
+		    %% that all three become aligned vertically)
+		    rewrite(above(nest(N1, floating(D, H, V)),
+				  above(floating(D2, H1, V1),
+					D1)),
+			    C2);
+		#c_float_above_nest{d = D2, h = H1, v = V1,
+				    i = _N1, c = C2}
+		when V1 == V, H1 /= H ->
+		    %% Align horizontally
+		    rewrite(beside(floating(D2, H1, V1),
+				   beside(floating(D, H, V),
+					  D1)),
+			    C2);
+		_ ->
+		    rewrite(D1, #c_float_beside{d = D, h = H,
+						v = V, c = C1})
+	    end;
+	#c_above_nest{d = D1, i = N, c = C1} ->
+	    case C1 of
+		#c_float_beside{d = D2, h = H1, v = V1, c = C2}
+		when H1 > H ->
+		    %% Move left (indentation is lost; note that
+		    %% all three become aligned horizontally)
+		    rewrite(beside(floating(D, H, V),
+				   beside(floating(D2, H1, V1),
+					  D1)),
+			    C2);
+		#c_float_beside{d = D2, h = H1, v = V1, c = C2}
+		when V1 /= V ->
+		    %% Align vertically
+		    rewrite(above(floating(D2, H1, V1),
+				  above(floating(D, H, V),
+					nest(N, D1))),
+			    C2);
+		#c_float_above_nest{d = D2, h = H1, v = V1,
+				    i = N1, c = C2}
+		when V1 > V ->
+		    %% Move up (note the indentation)
+		    rewrite(above(nest(N1, floating(D, H, V)),
+				  above(floating(D2, H1, V1),
+					nest(N + N1, D1))),
+			    C2);
+		#c_float_above_nest{d = D2, h = H1, v = V1,
+				    i = _N1, c = C2}
+		when V1 == V, H1 /= H ->
+		    %% Align horizontally
+		    rewrite(beside(
+			      floating(D2, H1, V1),
+			      above(floating(D, H, V),
+				    nest(N, D1))),
+			    C2);
+		_ ->
+		    rewrite(D1, #c_float_above_nest{d = D, h = H,
+						    v = V, i = N,
+						    c = C1})
+	    end;
+	#c_fit{c = C1} ->
+	    rewrite(floating(fit(D), H, V), C1);
+	#c_float_beside{d = D1, h = H1, v = V1, c = C1} ->
+	    if H1 > H ->
+		    %% Swap
+		    rewrite(beside(floating(D, H, V),
+				   floating(D1, H1, V1)),
+			    C1);
+	       V1 /= V ->
+		    %% Align vertically
+		    rewrite(above(floating(D, H, V),
+				  floating(D1, H1, V1)),
+			    C1);
+	       true ->
+		    %% Drop the 'float' wrapper of the rightmost.
+		    rewrite(beside(floating(D1, H1, V1), D), C1)
+	    end;
+	#c_float_above_nest{d = D1, h = H1, v = V1, i = N,
+			    c = C1} ->
+	    if V1 > V ->
+		    %% Swap (note the indentation)
+		    rewrite(above(nest(N, floating(D, H, V)),
+				  floating(D1, H1, V1)),
+			    C1);
+	       V1 == V, H1 /= H ->
+		    %% Align horizontally
+		    rewrite(beside(floating(D, H, V),
+				   floating(D1, H1, V1)),
+			    C1);
+	       true ->
+		    %% Drop the 'float' wrapper of the lower.
+		    rewrite(above(floating(D1, H1, V1),
+				  nest(N, D)),
+			    C1)
+	    end;
+	_ ->
+	    %% All other cases simply drop the `float' wrapper.
+	    rewrite(D, C)
+    end;
+rewrite(null, C) ->
+    case C of
+	#c_best_nest{} ->
+	    null;    % done
+	#c_above_nest{d = D, i = N, c = C1} ->
+	    rewrite(nest(N, D), C1);
+	#c_beside{d = D, c = C1} ->
+	    rewrite(D, C1);
+	#c_text_beside{s = S, c = C1} ->
+	    rewrite(mktext(S), C1);
+	#c_sep_nest{} ->
+	    %% In a `nest' context, an empty document behaves like
+	    %% the empty string.
+	    rewrite(nil(), C);
+	#c_best_nest_or{w = W, r = R, i = N} ->
+	    %% An empty document as "nice" as it can be, so we
+	    %% discard the alternative.
+	    rewrite(null, #c_best_nest{w = W, r = R, i = N});
+	#c_fit{c = C1} ->
+	    rewrite(null, C1);    % identity
+	#c_float_beside{d = D, h = _H, v = _V, c = C1} ->
+	    %% We just remove the float wrapper; cf. below.
+	    rewrite(beside(D, null), C1);
+	#c_float_above_nest{d = D, h = _H, v = _V, i = N, c = C1} ->
+	    %% It is important that this case just removes the
+	    %% float wrapper; the empty document must be preserved
+	    %% until later, or it will not be useful for forcing
+	    %% line breaks.
+	    rewrite(above(D, nest(N, null)), C1)
+    end.
+
+%% Both `null' and `empty' are already in use, so what do you do?
+
+nil() ->
+    text("").
+
+hspace() ->
+    text([$\s]).
+
+union(D1, D2) ->
+    #union{d1 = D1, d2 = D2}.
+
+fit(D) ->
+    #fit{d = D}.
+
+enter_sep(Ds, N, P, C) ->
+    case Ds of
+	[D] ->
+	    rewrite(D, C);    % Handle this case separately
+	[D | Ds1] ->
+	    %% Note that we never build a `sep'-context with an
+	    %% empty "tail" list! `Ds1' is nonempty here!
+	    rewrite(D, #c_sep_nest{ds = Ds1, i = N, p = P, c = C})
+    end.
+
+%% When we expand a `sep', the extra indentation appears as `nest'
+%% operators, but not until then.
+
+expand_sep(D, Ds, N) ->
+    union(fit(horizontal([D | Ds])),
+	  vertical([D | [nest(N, D1) || D1 <- Ds]])).
+
+expand_par(D, [D1 | Ds] = DL, N) ->
+    union(beside(fit(D),
+		 beside(hspace(),
+			mksep([fit(D1) | Ds], N - 1, true))),
+	  above(D, nest(N, par(DL)))).
+
+horizontal(Ds) ->
+    foldr1(fun (D1, D2) ->
+		   beside(D1, beside(hspace(), D2))
+	   end, Ds).
+
+vertical(Ds) ->
+    foldr1(fun above/2, Ds).
+
+foldr1(_F, [H]) ->
+    H;
+foldr1(F, [H | T]) ->
+    F(H, foldr1(F, T)).
+
+%% Internal representation of strings; stores the field width and does
+%% not perform list concatenation until the text is requested. Strings
+%% are thus deep lists whose first element is the length of the string.
+%% Null strings are strings whose "official width" is zero, typically
+%% used for markup that is not supposed to affect the indentation.
+
+string(S) ->
+    [strwidth(S) | S].
+
+null_string(S) ->
+    [0 | S].
+
+concat([_ | []], [_ | _] = S) ->
+    S;
+concat([_ | _] = S, [_ | []]) ->
+    S;
+concat([L1 | S1], [L2 | S2]) ->
+    [L1 + L2 | [S1 | S2]].
+
+string_chars([_ | S]) ->
+    S.
+
+width(S) ->
+    hd(S).
+
+is_empty_string([_ | []]) ->
+    true;
+is_empty_string([_ | _]) ->
+    false.
+
+%% We need to use `strwidth' instead of list `length', to properly
+%% handle Tab characters in the text segments. Note that the width of
+%% tabs is hard-coded as 8 character positions, and that strings are
+%% individually considered to be aligned at column 0; Tab characters are
+%% not really nice to give to a prettyprinter, and this seems to be the
+%% best interpretation.
+
+strwidth(S) ->
+    strwidth(S, 0).
+
+strwidth([$\t | Cs], N) ->
+    strwidth(Cs, N - (N rem 8) + 8);
+strwidth([_ | Cs], N) ->
+    strwidth(Cs, N + 1);
+strwidth([], N) ->
+    N.
+
+%% =====================================================================
diff --git a/lib/syntax_tools/src/syntax_tools.app.src b/lib/syntax_tools/src/syntax_tools.app.src
new file mode 100644
index 0000000000..dc0b9edd62
--- /dev/null
+++ b/lib/syntax_tools/src/syntax_tools.app.src
@@ -0,0 +1,17 @@
+% This is an -*- erlang -*- file.
+
+{application, syntax_tools,
+ [{description, "Syntax tools"},
+  {vsn, "%VSN%"},
+  {modules, [epp_dodger,
+	     erl_comment_scan,
+	     erl_prettypr,
+	     erl_recomment,
+	     erl_syntax,
+	     erl_syntax_lib,
+	     erl_tidy,
+	     igor,
+	     prettypr]},
+  {registered,[]},
+  {applications, [stdlib]},
+  {env, []}]}.
diff --git a/lib/syntax_tools/src/syntax_tools.appup.src b/lib/syntax_tools/src/syntax_tools.appup.src
new file mode 100644
index 0000000000..54a63833e6
--- /dev/null
+++ b/lib/syntax_tools/src/syntax_tools.appup.src
@@ -0,0 +1 @@
+{"%VSN%",[],[]}.