Extend char() to Unicode characters

The code related to the introduction of unicode_string() and
unicode_char() has been removed. The types char() and string() have
been extended to include Unicode characters.

In fact char() was changed some time ago; this commit is about
cleaning up the documentation and introduce better names for some
functions.

19 files changed, 258 insertions, 227 deletions

diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/inets b/lib/dialyzer/test/r9c_SUITE_data/results/inets
index d789d8d246..629378d673 100644
--- a/lib/dialyzer/test/r9c_SUITE_data/results/inets
+++ b/lib/dialyzer/test/r9c_SUITE_data/results/inets
@@ -35,7 +35,7 @@ mod_auth_plain.erl:159: The variable _ can never match since previous clauses co
 mod_auth_plain.erl:83: The variable O can never match since previous clauses completely covered the type [[any()]]
 mod_cgi.erl:372: The pattern {'http_response', NewAccResponse} can never match the type 'ok'
 mod_dir.erl:101: The call lists:flatten(nonempty_improper_list(atom() | [any()] | char(),atom())) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
-mod_dir.erl:72: The pattern {'error', Reason} can never match the type {'ok',[[[any()] | non_neg_integer()],...]}
+mod_dir.erl:72: The pattern {'error', Reason} can never match the type {'ok',[[[any()] | char()],...]}
 mod_get.erl:135: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | [any()] | char()]>
 mod_head.erl:80: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | [any()] | char()]>
 mod_htaccess.erl:460: The pattern {'error', BadData} can never match the type {'ok',_}
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 7631f5289e..0f88b32db1 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -2,7 +2,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2003-2012. All Rights Reserved.
+%% Copyright Ericsson AB 2003-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -63,7 +63,6 @@
 	 t_boolean/0,
 	 t_byte/0,
 	 t_char/0,
-	 t_charlist/0,
 	 t_collect_vars/1,
 	 t_cons/0,
 	 t_cons/2,
@@ -197,7 +196,6 @@
 	 t_tuple_size/1,
 	 t_tuple_sizes/1,
 	 t_tuple_subtypes/1,
-	 t_unicode_string/0,
 	 t_unify/2,
 	 t_unify/3,
 	 t_unit/0,
@@ -1458,21 +1456,6 @@ t_is_tuple(_) -> false.
 t_bitstrlist() ->
   t_iolist(1, t_bitstr()).
 
--spec t_charlist() -> erl_type().
-
-t_charlist() ->
-  t_charlist(1).
-
--spec t_charlist(non_neg_integer()) -> erl_type().
-
-t_charlist(N) when N > 0 ->
-  t_maybe_improper_list(t_sup([t_unicode_char(),
-			       t_unicode_binary(),
-			       t_charlist(N-1)]),
-		        t_sup(t_unicode_binary(), t_nil()));
-t_charlist(0) ->
-  t_maybe_improper_list(t_any(), t_sup(t_unicode_binary(), t_nil())).
-
 -spec t_constant() -> erl_type().
 
 t_constant() ->
@@ -1568,21 +1551,6 @@ t_parameterized_module() ->
 t_timeout() ->
   t_sup(t_non_neg_integer(), t_atom('infinity')).
 
--spec t_unicode_binary() -> erl_type().
-
-t_unicode_binary() ->
-  t_binary().  % with characters encoded in UTF-8 coding standard
-
--spec t_unicode_char() -> erl_type().
-
-t_unicode_char() ->
-  t_integer(). % representing a valid unicode codepoint
-
--spec t_unicode_string() -> erl_type().
-
-t_unicode_string() ->
-  t_list(t_unicode_char()).
-
 %%-----------------------------------------------------------------------------
 %% Some built-in opaque types
 %%
diff --git a/lib/parsetools/include/yeccpre.hrl b/lib/parsetools/include/yeccpre.hrl
index e4c3ba52be..855bff5fdc 100644
--- a/lib/parsetools/include/yeccpre.hrl
+++ b/lib/parsetools/include/yeccpre.hrl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -36,7 +36,7 @@ parse_and_scan({M, F, A}) ->
 
 -spec format_error(any()) -> [char() | list()].
 format_error(Message) ->
-    case io_lib:deep_unicode_char_list(Message) of
+    case io_lib:deep_char_list(Message) of
         true ->
             Message;
         _ ->
@@ -164,9 +164,9 @@ yecctoken_location(Token) ->
 yecctoken2string({atom, _, A}) -> io_lib:write(A);
 yecctoken2string({integer,_,N}) -> io_lib:write(N);
 yecctoken2string({float,_,F}) -> io_lib:write(F);
-yecctoken2string({char,_,C}) -> io_lib:write_unicode_char(C);
+yecctoken2string({char,_,C}) -> io_lib:write_char(C);
 yecctoken2string({var,_,V}) -> io_lib:format("~s", [V]);
-yecctoken2string({string,_,S}) -> io_lib:write_unicode_string(S);
+yecctoken2string({string,_,S}) -> io_lib:write_string(S);
 yecctoken2string({reserved_symbol, _, A}) -> io_lib:write(A);
 yecctoken2string({_Cat, _, Val}) -> io_lib:format("~p",[Val]);
 yecctoken2string({dot, _}) -> "'.'";
diff --git a/lib/parsetools/src/leex.erl b/lib/parsetools/src/leex.erl
index bbef4053b4..32c513f56c 100644
--- a/lib/parsetools/src/leex.erl
+++ b/lib/parsetools/src/leex.erl
@@ -1669,7 +1669,7 @@ quote($\d) -> "\\\\d";
 quote($\\) -> "\\\\";
 quote(C) when is_integer(C) ->
     %% Must remove the $ and get the \'s right.
-    case io_lib:write_unicode_char(C) of
+    case io_lib:write_char(C) of
         [$$,$\\|Cs] -> "\\\\" ++ Cs;
         [$$|Cs] -> Cs
     end;
diff --git a/lib/parsetools/src/yecc.erl b/lib/parsetools/src/yecc.erl
index dbb7d025ae..2f0f70f39b 100644
--- a/lib/parsetools/src/yecc.erl
+++ b/lib/parsetools/src/yecc.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -2494,8 +2494,8 @@ pp_tokens1([T | Ts], Line0, Enc, T0) ->
 
 pp_symbol({var,_,Var}, _Enc) -> Var;
 pp_symbol({string,_,String}, latin1) ->
-    io_lib:write_unicode_string_as_latin1(String);
-pp_symbol({string,_,String}, _Enc) -> io_lib:write_unicode_string(String);
+    io_lib:write_string_as_latin1(String);
+pp_symbol({string,_,String}, _Enc) -> io_lib:write_string(String);
 pp_symbol({_,_,Symbol}, latin1) -> io_lib:fwrite(<<"~p">>, [Symbol]);
 pp_symbol({_,_,Symbol}, _Enc) -> io_lib:fwrite(<<"~tp">>, [Symbol]);
 pp_symbol({Symbol, _}, _Enc) -> Symbol.
diff --git a/lib/parsetools/src/yeccparser.erl b/lib/parsetools/src/yeccparser.erl
index e4b8b06db5..54f9ba5a58 100644
--- a/lib/parsetools/src/yeccparser.erl
+++ b/lib/parsetools/src/yeccparser.erl
@@ -17,7 +17,7 @@ line_of(Token) ->
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -178,7 +178,7 @@ yecctoken2string({integer,_,N}) -> io_lib:write(N);
 yecctoken2string({float,_,F}) -> io_lib:write(F);
 yecctoken2string({char,_,C}) -> io_lib:write_char(C);
 yecctoken2string({var,_,V}) -> io_lib:format("~s", [V]);
-yecctoken2string({string,_,S}) -> io_lib:write_unicode_string(S);
+yecctoken2string({string,_,S}) -> io_lib:write_string(S);
 yecctoken2string({reserved_symbol, _, A}) -> io_lib:write(A);
 yecctoken2string({_Cat, _, Val}) -> io_lib:write(Val);
 yecctoken2string({dot, _}) -> "'.'";
diff --git a/lib/stdlib/doc/src/io_lib.xml b/lib/stdlib/doc/src/io_lib.xml
index 7487cb5740..001d34a7c2 100644
--- a/lib/stdlib/doc/src/io_lib.xml
+++ b/lib/stdlib/doc/src/io_lib.xml
@@ -4,7 +4,7 @@
 <erlref>
   <header>
     <copyright>
-      <year>1996</year><year>2012</year>
+      <year>1996</year><year>2013</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -53,6 +53,9 @@
     <datatype>
       <name name="fread_error"/>
     </datatype>
+    <datatype>
+      <name name="latin1_string"/>
+    </datatype>
   </datatypes>
   <funcs>
     <func>
@@ -207,8 +210,25 @@
       <name name="write_string" arity="1"/>
       <fsummary>Write a string</fsummary>
       <desc>
-        <p>Returns the list of characters needed to print <c><anno>String</anno></c>
-          as a string.</p>
+        <p>Returns the list of characters needed to print
+          <c><anno>String</anno></c> as a string.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="write_string_as_latin1" arity="1"/>
+      <fsummary>Write a string</fsummary>
+      <desc>
+        <p>Returns the list of characters needed to print
+          <c><anno>String</anno></c> as a string. Non-Latin-1
+          characters are escaped.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="write_latin1_string" arity="1"/>
+      <fsummary>Write an ISO-latin-1 string</fsummary>
+      <desc>
+        <p>Returns the list of characters needed to print
+          <c><anno>Latin1String</anno></c> as a string.</p>
       </desc>
     </func>
     <func>
@@ -216,6 +236,23 @@
       <fsummary>Write a character</fsummary>
       <desc>
         <p>Returns the list of characters needed to print a character
+          constant in the Unicode character set.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="write_char_as_latin1" arity="1"/>
+      <fsummary>Write a character</fsummary>
+      <desc>
+        <p>Returns the list of characters needed to print a character
+          constant in the Unicode character set. Non-Latin-1 characters
+          are escaped.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="write_latin1_char" arity="1"/>
+      <fsummary>Write an ISO-latin-1 character</fsummary>
+      <desc>
+        <p>Returns the list of characters needed to print a character
           constant in the ISO-latin-1 character set.</p>
       </desc>
     </func>
@@ -232,6 +269,14 @@
       <fsummary>Test for a list of characters</fsummary>
       <desc>
         <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a flat list of
+          characters in the Unicode range, otherwise it returns <c>false</c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="latin1_char_list" arity="1"/>
+      <fsummary>Test for a list of ISO-latin-1 characters</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a flat list of
           characters in the ISO-latin-1 range, otherwise it returns <c>false</c>.</p>
       </desc>
     </func>
@@ -240,11 +285,27 @@
       <fsummary>Test for a deep list of characters</fsummary>
       <desc>
         <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a, possibly deep, list
+          of characters in the Unicode range, otherwise it returns <c>false</c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="deep_latin1_char_list" arity="1"/>
+      <fsummary>Test for a deep list of characters</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a, possibly deep, list
           of characters in the ISO-latin-1 range, otherwise it returns <c>false</c>.</p>
       </desc>
     </func>
     <func>
       <name name="printable_list" arity="1"/>
+      <fsummary>Test for a list of printable characters</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a flat list of
+          printable Unicode characters, otherwise it returns <c>false</c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name name="printable_latin1_list" arity="1"/>
       <fsummary>Test for a list of printable ISO-latin-1 characters</fsummary>
       <desc>
         <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a flat list of
diff --git a/lib/stdlib/doc/src/unicode.xml b/lib/stdlib/doc/src/unicode.xml
index d235f3e180..deba6adb11 100644
--- a/lib/stdlib/doc/src/unicode.xml
+++ b/lib/stdlib/doc/src/unicode.xml
@@ -5,7 +5,7 @@
   <header>
     <copyright>
       <year>1996</year>
-      <year>2012</year>
+      <year>2013</year>
       <holder>Ericsson AB, All Rights Reserved</holder>
     </copyright>
     <legalnotice>
@@ -52,19 +52,10 @@
       </desc>
     </datatype>
     <datatype>
-      <name name="unicode_char"/>
-      <desc>
-        <p>An <c>integer()</c> representing a valid Unicode codepoint.</p>
-      </desc>
-    </datatype>
-    <datatype>
       <name name="chardata"/>
     </datatype>
     <datatype>
       <name name="charlist"/>
-      <desc>
-        <p>A <c>unicode_binary()</c> is allowed as the tail of the list.</p>
-      </desc>
     </datatype>
     <datatype>
       <name name="external_unicode_binary"/>
@@ -78,10 +69,6 @@
     </datatype>
     <datatype>
       <name name="external_charlist"/>
-      <desc>
-        <p>An <c>external_unicode_binary()</c> is allowed as the tail
-           of the list.</p>
-      </desc>
     </datatype>
     <datatype>
       <name name="latin1_binary"/>
@@ -96,11 +83,12 @@
     </datatype>
     <datatype>
       <name name="latin1_chardata"/>
+      <desc><p>The same as <c>iodata()</c>.</p>
+      </desc>
     </datatype>
     <datatype>
       <name name="latin1_charlist"/>
-      <desc><p>A <c>latin1_binary()</c> is allowed as the tail of
-        the list.</p>
+      <desc><p>The same as <c>iolist()</c>.</p>
       </desc>
     </datatype>
   </datatypes>
diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index ebabf8d700..475b1bf933 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -1276,9 +1276,9 @@ token_src({X, _}) when is_atom(X) ->
 token_src({var, _, X}) ->
     atom_to_list(X);
 token_src({char,_,C}) ->
-    io_lib:write_unicode_char(C);
+    io_lib:write_char(C);
 token_src({string, _, X}) ->
-    io_lib:write_unicode_string(X);
+    io_lib:write_string(X);
 token_src({_, _, X}) ->
     io_lib:format("~w", [X]).
 
diff --git a/lib/stdlib/src/erl_pp.erl b/lib/stdlib/src/erl_pp.erl
index 0e1156075a..a868867a81 100644
--- a/lib/stdlib/src/erl_pp.erl
+++ b/lib/stdlib/src/erl_pp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -179,12 +179,12 @@ state(_Hook) ->
     state().
 
 state() ->
-    #pp{string_fun = fun io_lib:write_unicode_string_as_latin1/1,
-        char_fun   = fun io_lib:write_unicode_char_as_latin1/1}.
+    #pp{string_fun = fun io_lib:write_string_as_latin1/1,
+        char_fun   = fun io_lib:write_char_as_latin1/1}.
 
 unicode_state() ->
-    #pp{string_fun = fun io_lib:write_unicode_string/1,
-        char_fun   = fun io_lib:write_unicode_char/1}.
+    #pp{string_fun = fun io_lib:write_string/1,
+        char_fun   = fun io_lib:write_char/1}.
 
 encoding(Options) ->
     case proplists:get_value(encoding, Options, epp:default_encoding()) of
diff --git a/lib/stdlib/src/erl_scan.erl b/lib/stdlib/src/erl_scan.erl
index bc0eaf015d..f4accde8e7 100644
--- a/lib/stdlib/src/erl_scan.erl
+++ b/lib/stdlib/src/erl_scan.erl
@@ -2,7 +2,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -115,7 +115,7 @@
 format_error({string,Quote,Head}) ->
     lists:flatten(["unterminated " ++ string_thing(Quote) ++
                    " starting with " ++
-                   io_lib:write_unicode_string(Head, Quote)]);
+                   io_lib:write_string(Head, Quote)]);
 format_error({illegal,Type}) ->
     lists:flatten(io_lib:fwrite("illegal ~w", [Type]));
 format_error(char) -> "unterminated character";
diff --git a/lib/stdlib/src/io.erl b/lib/stdlib/src/io.erl
index 9b436c224c..79cb988c5d 100644
--- a/lib/stdlib/src/io.erl
+++ b/lib/stdlib/src/io.erl
@@ -127,7 +127,7 @@ rows(Io) ->
 -spec get_chars(Prompt, Count) -> Data | server_no_data() when
       Prompt :: prompt(),
       Count :: non_neg_integer(),
-      Data :: [unicode:unicode_char()] | unicode:unicode_binary().
+      Data :: string() | unicode:unicode_binary().
 
 get_chars(Prompt, N) ->
     get_chars(default_input(), Prompt, N).
@@ -136,14 +136,14 @@ get_chars(Prompt, N) ->
       IoDevice :: device(),
       Prompt :: prompt(),
       Count :: non_neg_integer(),
-      Data :: [unicode:unicode_char()] | unicode:unicode_binary().
+      Data :: string() | unicode:unicode_binary().
 
 get_chars(Io, Prompt, N) when is_integer(N), N >= 0 ->
     request(Io, {get_chars,unicode,Prompt,N}).
 
 -spec get_line(Prompt) -> Data | server_no_data() when
       Prompt :: prompt(),
-      Data :: [unicode:unicode_char()] | unicode:unicode_binary().
+      Data :: string() | unicode:unicode_binary().
 
 get_line(Prompt) ->
     get_line(default_input(), Prompt).
@@ -151,7 +151,7 @@ get_line(Prompt) ->
 -spec get_line(IoDevice, Prompt) -> Data | server_no_data() when
       IoDevice :: device(),
       Prompt :: prompt(),
-      Data :: [unicode:unicode_char()] | unicode:unicode_binary().
+      Data :: string() | unicode:unicode_binary().
 
 get_line(Io, Prompt) ->
     request(Io, {get_line,unicode,Prompt}).
diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index df5f9b8c25..b7ec848e1e 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -64,29 +64,31 @@
 -export([print/1,print/4,indentation/2]).
 
 -export([write/1,write/2,write/3,nl/0,format_prompt/1,format_prompt/2]).
--export([write_atom/1,write_string/1,write_string/2,write_unicode_string/1,
-         write_unicode_string/2, write_char/1, write_unicode_char/1]).
+-export([write_atom/1,write_string/1,write_string/2,write_latin1_string/1,
+         write_latin1_string/2, write_char/1, write_latin1_char/1]).
 
--export([write_unicode_string_as_latin1/1, write_unicode_string_as_latin1/2,
-         write_unicode_char_as_latin1/1]).
+-export([write_string_as_latin1/1, write_string_as_latin1/2,
+         write_char_as_latin1/1]).
 
--export([quote_atom/2, char_list/1, unicode_char_list/1,
-	 deep_char_list/1, deep_unicode_char_list/1,
-	 printable_list/1, printable_unicode_list/1]).
+-export([quote_atom/2, char_list/1, latin1_char_list/1,
+	 deep_char_list/1, deep_latin1_char_list/1,
+	 printable_list/1, printable_latin1_list/1]).
 
 %% Utilities for collecting characters.
 -export([collect_chars/3, collect_chars/4,
 	 collect_line/2, collect_line/3, collect_line/4,
 	 get_until/3, get_until/4]).
 
--export_type([chars/0, unicode_chars/0, unicode_string/0, continuation/0,
-              fread_error/0]).
+%% The following functions were used by Yecc's include-file.
+-export([write_unicode_string/1, write_unicode_char/1,
+         deep_unicode_char_list/1]).
+
+-export_type([chars/0, latin1_string/0, continuation/0, fread_error/0]).
 
 %%----------------------------------------------------------------------
 
 -type chars() :: [char() | chars()].
--type unicode_chars() :: [unicode:unicode_char() | unicode_chars()].
--type unicode_string() :: [unicode:unicode_char()].
+-type latin1_string() :: [unicode:latin1_char()].
 -type depth() :: -1 | non_neg_integer().
 
 -opaque continuation() :: {Format :: string(),
@@ -108,10 +110,8 @@
 
 %% Interface calls to sub-modules.
 
--spec fwrite(Format, Data) -> chars() | UnicodeList when
+-spec fwrite(Format, Data) -> chars() when
       Format :: io:format(),
-      Data :: [term()],
-      UnicodeList :: [unicode:unicode_char()],
       Data :: [term()].
 
 fwrite(Format, Args) ->
@@ -142,10 +142,9 @@ fread(Chars, Format) ->
 fread(Cont, Chars, Format) ->
     io_lib_fread:fread(Cont, Chars, Format).
 
--spec format(Format, Data) -> chars() | UnicodeList when
+-spec format(Format, Data) -> chars() when
       Format :: io:format(),
-      Data :: [term()],
-      UnicodeList :: [unicode:unicode_char()].
+      Data :: [term()].
 
 format(Format, Args) ->
     case catch io_lib_format:fwrite(Format, Args) of
@@ -340,6 +339,11 @@ name_char($_) -> true;
 name_char($@) -> true;
 name_char(_) -> false.
 
+%%% There are two functions to write Unicode strings:
+%%% - they both escape control characters < 160;
+%%% - write_string() never escapes characters >= 160;
+%%% - write_string_as_latin1() also escapes characters >= 255.
+
 %% write_string([Char]) -> [Char]
 %%  Generate the list of characters needed to print a string.
 
@@ -352,33 +356,32 @@ write_string(S) ->
 -spec write_string(string(), char()) -> chars().
 
 write_string(S, Q) ->
-    [Q|write_string1(latin1, S, Q)].
+    [Q|write_string1(unicode_as_unicode, S, Q)].
 
-%%% There are two functions to write Unicode strings:
-%%% - they both escape control characters < 160;
-%%% - write_unicode_string() never escapes characters >= 160;
-%%% - write_unicode_string_as_latin1() also escapes characters >= 255.
+%% Backwards compatibility.
+write_unicode_string(S) ->
+    write_string(S).
 
--spec write_unicode_string(UnicodeString) -> unicode_string() when
-      UnicodeString :: unicode_string().
+-spec write_latin1_string(Latin1String) -> latin1_string() when
+      Latin1String :: latin1_string().
 
-write_unicode_string(S) ->
-    write_unicode_string(S, $").   %"
+write_latin1_string(S) ->
+    write_latin1_string(S, $").   %"
 
--spec write_unicode_string(unicode_string(), char()) -> unicode_string().
+-spec write_latin1_string(latin1_string(), char()) -> latin1_string().
 
-write_unicode_string(S, Q) ->
-    [Q|write_string1(unicode_as_unicode, S, Q)].
+write_latin1_string(S, Q) ->
+    [Q|write_string1(latin1, S, Q)].
 
--spec write_unicode_string_as_latin1(UnicodeString) -> string() when
-      UnicodeString :: unicode_string().
+-spec write_string_as_latin1(String) -> latin1_string() when
+      String :: string().
 
-write_unicode_string_as_latin1(S) ->
-    write_unicode_string_as_latin1(S, $").   %"
+write_string_as_latin1(S) ->
+    write_string_as_latin1(S, $").   %"
 
--spec write_unicode_string_as_latin1(unicode_string(), char()) -> string().
+-spec write_string_as_latin1(string(), char()) -> latin1_string().
 
-write_unicode_string_as_latin1(S, Q) ->
+write_string_as_latin1(S, Q) ->
     [Q|write_string1(unicode_as_latin1, S, Q)].
 
 write_string1(_,[], Q) ->
@@ -412,6 +415,11 @@ string_char(_,C, _, Tail) when C < $\240->	%Other control characters.
     C3 = (C band 7) + $0,
     [$\\,C1,C2,C3|Tail].
 
+%%% There are two functions to write a Unicode character:
+%%% - they both escape control characters < 160;
+%%% - write_char() never escapes characters >= 160;
+%%% - write_char_as_latin1() also escapes characters >= 255.
+
 %% write_char(Char) -> [char()].
 %%  Generate the list of characters needed to print a character constant.
 %%  Must special case SPACE, $\s, here.
@@ -420,48 +428,63 @@ string_char(_,C, _, Tail) when C < $\240->	%Other control characters.
       Char :: char().
 
 write_char($\s) -> "$\\s";			%Must special case this.
-write_char(C) when is_integer(C), C >= $\000, C =< $\377 ->
-    [$$|string_char(latin1,C, -1, [])].
+write_char(C) when is_integer(C), C >= $\000 ->
+    [$$|string_char(unicode_as_unicode, C, -1, [])].
 
-%%% There are two functions to write a Unicode character:
-%%% - they both escape control characters < 160;
-%%% - write_unicode_char() never escapes characters >= 160;
-%%% - write_unicode_char_as_latin1() also escapes characters >= 255.
+%% Backwards compatibility.
+write_unicode_char(C) ->
+    write_char(C).
 
--spec write_unicode_char(UnicodeChar) -> unicode_string() when
-      UnicodeChar :: unicode:unicode_char().
+-spec write_latin1_char(Latin1Char) -> latin1_string() when
+      Latin1Char :: unicode:latin1_char().
 
-write_unicode_char(Uni) when is_integer(Uni), Uni >= $\000 ->
-    [$$|string_char(unicode_as_unicode,Uni, -1, [])].
+write_latin1_char(Lat1) when is_integer(Lat1), Lat1 >= $\000, Lat1 =< $\377  ->
+    [$$|string_char(latin1, Lat1, -1, [])].
 
--spec write_unicode_char_as_latin1(UnicodeChar) -> string() when
-      UnicodeChar :: unicode:unicode_char().
+-spec write_char_as_latin1(Char) -> latin1_string() when
+      Char :: char().
 
-write_unicode_char_as_latin1(Uni) when is_integer(Uni), Uni >= $\000 ->
+write_char_as_latin1(Uni) when is_integer(Uni), Uni >= $\000 ->
     [$$|string_char(unicode_as_latin1,Uni, -1, [])].
 
-%% char_list(CharList)
-%% deep_char_list(CharList)
-%%  Return true if CharList is a (possibly deep) list of characters, else
-%%  false.
+%% latin1_char_list(CharList)
+%% deep_latin1_char_list(CharList)
+%%  Return true if CharList is a (possibly deep) list of Latin-1
+%%  characters, else false.
+
+-spec latin1_char_list(Term) -> boolean() when
+      Term :: term().
+
+latin1_char_list([C|Cs]) when is_integer(C), C >= $\000, C =< $\377 ->
+    latin1_char_list(Cs);
+latin1_char_list([]) -> true;
+latin1_char_list(_) -> false.			%Everything else is false
 
 -spec char_list(Term) -> boolean() when
       Term :: term().
 
-char_list([C|Cs]) when is_integer(C), C >= $\000, C =< $\377 ->
+char_list([C|Cs]) when is_integer(C), C >= 0, C < 16#D800;
+       is_integer(C), C > 16#DFFF, C < 16#FFFE;
+       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
     char_list(Cs);
 char_list([]) -> true;
 char_list(_) -> false.			%Everything else is false
 
--spec unicode_char_list(Term) -> boolean() when
+-spec deep_latin1_char_list(Term) -> boolean() when
       Term :: term().
 
-unicode_char_list([C|Cs]) when is_integer(C), C >= 0, C < 16#D800; 
-       is_integer(C), C > 16#DFFF, C < 16#FFFE;
-       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
-    unicode_char_list(Cs);
-unicode_char_list([]) -> true;
-unicode_char_list(_) -> false.			%Everything else is false
+deep_latin1_char_list(Cs) ->
+    deep_latin1_char_list(Cs, []).
+
+deep_latin1_char_list([C|Cs], More) when is_list(C) ->
+    deep_latin1_char_list(C, [Cs|More]);
+deep_latin1_char_list([C|Cs], More) when is_integer(C), C >= $\000, C =< $\377 ->
+    deep_latin1_char_list(Cs, More);
+deep_latin1_char_list([], [Cs|More]) ->
+    deep_latin1_char_list(Cs, More);
+deep_latin1_char_list([], []) -> true;
+deep_latin1_char_list(_, _More) ->			%Everything else is false
+    false.
 
 -spec deep_char_list(Term) -> boolean() when
       Term :: term().
@@ -471,43 +494,56 @@ deep_char_list(Cs) ->
 
 deep_char_list([C|Cs], More) when is_list(C) ->
     deep_char_list(C, [Cs|More]);
-deep_char_list([C|Cs], More) when is_integer(C), C >= $\000, C =< $\377 ->
+deep_char_list([C|Cs], More)
+  when is_integer(C), C >= 0, C < 16#D800;
+       is_integer(C), C > 16#DFFF, C < 16#FFFE;
+       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
     deep_char_list(Cs, More);
 deep_char_list([], [Cs|More]) ->
     deep_char_list(Cs, More);
 deep_char_list([], []) -> true;
-deep_char_list(_, _More) ->			%Everything else is false
+deep_char_list(_, _More) ->		%Everything else is false
     false.
 
--spec deep_unicode_char_list(Term) -> boolean() when
-      Term :: term().
+deep_unicode_char_list(Term) ->
+    deep_char_list(Term).
 
-deep_unicode_char_list(Cs) ->
-    deep_unicode_char_list(Cs, []).
+%% printable_latin1_list([Char]) -> boolean()
+%%  Return true if CharList is a list of printable Latin1 characters, else
+%%  false.
 
-deep_unicode_char_list([C|Cs], More) when is_list(C) ->
-    deep_unicode_char_list(C, [Cs|More]);
-deep_unicode_char_list([C|Cs], More) 
-  when is_integer(C), C >= 0, C < 16#D800; 
-       is_integer(C), C > 16#DFFF, C < 16#FFFE;
-       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
-    deep_unicode_char_list(Cs, More);
-deep_unicode_char_list([], [Cs|More]) ->
-    deep_unicode_char_list(Cs, More);
-deep_unicode_char_list([], []) -> true;
-deep_unicode_char_list(_, _More) ->		%Everything else is false
-    false.
+-spec printable_latin1_list(Term) -> boolean() when
+      Term :: term().
+
+printable_latin1_list([C|Cs]) when is_integer(C), C >= $\040, C =< $\176 ->
+    printable_latin1_list(Cs);
+printable_latin1_list([C|Cs]) when is_integer(C), C >= $\240, C =< $\377 ->
+    printable_latin1_list(Cs);
+printable_latin1_list([$\n|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\r|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\t|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\v|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\b|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\f|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([$\e|Cs]) -> printable_latin1_list(Cs);
+printable_latin1_list([]) -> true;
+printable_latin1_list(_) -> false.			%Everything else is false
 
 %% printable_list([Char]) -> boolean()
 %%  Return true if CharList is a list of printable characters, else
-%%  false.
+%%  false. The notion of printable in Unicode terms is somewhat floating.
+%%  Everything that is not a control character and not invalid unicode
+%%  will be considered printable.
 
 -spec printable_list(Term) -> boolean() when
       Term :: term().
 
 printable_list([C|Cs]) when is_integer(C), C >= $\040, C =< $\176 ->
     printable_list(Cs);
-printable_list([C|Cs]) when is_integer(C), C >= $\240, C =< $\377 ->
+printable_list([C|Cs])
+  when is_integer(C), C >= 16#A0, C < 16#D800;
+       is_integer(C), C > 16#DFFF, C < 16#FFFE;
+       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
     printable_list(Cs);
 printable_list([$\n|Cs]) -> printable_list(Cs);
 printable_list([$\r|Cs]) -> printable_list(Cs);
@@ -517,33 +553,7 @@ printable_list([$\b|Cs]) -> printable_list(Cs);
 printable_list([$\f|Cs]) -> printable_list(Cs);
 printable_list([$\e|Cs]) -> printable_list(Cs);
 printable_list([]) -> true;
-printable_list(_) -> false.			%Everything else is false
-
-%% printable_unicode_list([Char]) -> boolean()
-%%  Return true if CharList is a list of printable characters, else
-%%  false. The notion of printable in Unicode terms is somewhat floating.
-%%  Everything that is not a control character and not invalid unicode 
-%%  will be considered printable.
-
--spec printable_unicode_list(Term) -> boolean() when
-      Term :: term().
-
-printable_unicode_list([C|Cs]) when is_integer(C), C >= $\040, C =< $\176 ->
-    printable_unicode_list(Cs);
-printable_unicode_list([C|Cs]) 
-  when is_integer(C), C >= 16#A0, C < 16#D800; 
-       is_integer(C), C > 16#DFFF, C < 16#FFFE;
-       is_integer(C), C > 16#FFFF, C =< 16#10FFFF ->
-    printable_unicode_list(Cs);
-printable_unicode_list([$\n|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\r|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\t|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\v|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\b|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\f|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([$\e|Cs]) -> printable_unicode_list(Cs);
-printable_unicode_list([]) -> true;
-printable_unicode_list(_) -> false.		%Everything else is false
+printable_list(_) -> false.		%Everything else is false
 
 %% List = nl()
 %%  Return a list of characters to generate a newline.
diff --git a/lib/stdlib/src/io_lib_format.erl b/lib/stdlib/src/io_lib_format.erl
index 5680f83ab6..6a06d9448b 100644
--- a/lib/stdlib/src/io_lib_format.erl
+++ b/lib/stdlib/src/io_lib_format.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %% 
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -22,7 +22,7 @@
 
 -export([fwrite/2,fwrite_g/1,indentation/2]).
 
-%% fwrite(Format, ArgList) -> [unicode:unicode:char()].
+%% fwrite(Format, ArgList) -> string().
 %%  Format the arguments in ArgList after string Format. Just generate
 %%  an error if there is an error in the arguments.
 %%
@@ -133,7 +133,7 @@ pcount([{$P,_As,_F,_Ad,_P,_Pad,_Enc}|Cs], Acc) -> pcount(Cs, Acc+1);
 pcount([_|Cs], Acc) -> pcount(Cs, Acc);
 pcount([], Acc) -> Acc.
 
-%% build([Control], Pc, Indentation) -> [unicode:unicode_char()].
+%% build([Control], Pc, Indentation) -> string().
 %%  Interpret the control structures. Count the number of print
 %%  remaining and only calculate indentation when necessary. Must also
 %%  be smart when calculating indentation for characters in format.
@@ -154,7 +154,7 @@ decr_pc($p, Pc) -> Pc - 1;
 decr_pc($P, Pc) -> Pc - 1;
 decr_pc(_, Pc) -> Pc.
 
-%% indentation([unicode:unicode_char()], Indentation) -> Indentation.
+%% indentation(String, Indentation) -> Indentation.
 %%  Calculate the indentation of the end of a string given its start
 %%  indentation. We assume tabs at 8 cols.
 
@@ -167,8 +167,7 @@ indentation([C|Cs], I) ->
 indentation([], I) -> I.
 
 %% control(FormatChar, [Argument], FieldWidth, Adjust, Precision, PadChar,
-%%	   Encoding, Indentation) ->
-%%	[unicode:unicode_char()]
+%%	   Encoding, Indentation) -> String
 %%  This is the main dispatch function for the various formatting commands.
 %%  Field widths and precisions have already been calculated.
 
@@ -613,7 +612,7 @@ prefixed_integer(Int, F, Adj, Base, Pad, Prefix, Lowercase)
 	    term([Prefix|S], F, Adj, none, Pad)
     end.
 
-%% char(Char, Field, Adjust, Precision, PadChar) -> [unicode:unicode_char()].
+%% char(Char, Field, Adjust, Precision, PadChar) -> string().
 
 char(C, none, _Adj, none, _Pad) -> [C];
 char(C, F, _Adj, none, _Pad) -> chars(C, F);
diff --git a/lib/stdlib/src/io_lib_pretty.erl b/lib/stdlib/src/io_lib_pretty.erl
index 99ad281a9b..dbf6fd74e4 100644
--- a/lib/stdlib/src/io_lib_pretty.erl
+++ b/lib/stdlib/src/io_lib_pretty.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %% 
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -51,7 +51,6 @@ print(Term) ->
 -type max_chars() :: integer().
 
 -type chars() :: io_lib:chars().
--type unicode_chars() :: io_lib:unicode_chars().
 -type option() :: {column, column()}
                 | {line_length, line_length()}
                 | {depth, depth()}
@@ -60,8 +59,8 @@ print(Term) ->
                 | {encoding, latin1 | utf8 | unicode}.
 -type options() :: [option()].
 
--spec print(term(), rec_print_fun()) -> chars() | unicode_chars();
-           (term(), options()) -> chars() | unicode_chars().
+-spec print(term(), rec_print_fun()) -> chars();
+           (term(), options()) -> chars().
 
 print(Term, Options) when is_list(Options) ->
     Col = proplists:get_value(column, Options, 1),
@@ -74,24 +73,23 @@ print(Term, Options) when is_list(Options) ->
 print(Term, RecDefFun) ->
     print(Term, -1, RecDefFun).
 
--spec print(term(), depth(), rec_print_fun()) -> chars() | unicode_chars().
+-spec print(term(), depth(), rec_print_fun()) -> chars().
 
 print(Term, Depth, RecDefFun) ->
     print(Term, 1, 80, Depth, RecDefFun).
 
--spec print(term(), column(), line_length(), depth()) ->
-                   chars() | unicode_chars().
+-spec print(term(), column(), line_length(), depth()) -> chars().
 
 print(Term, Col, Ll, D) ->
     print(Term, Col, Ll, D, _M=-1, no_fun, latin1).
 
 -spec print(term(), column(), line_length(), depth(), rec_print_fun()) ->
-                   chars() | unicode_chars().
+                   chars().
 print(Term, Col, Ll, D, RecDefFun) ->
     print(Term, Col, Ll, D, _M=-1, RecDefFun).
 
 -spec print(term(), column(), line_length(), depth(), max_chars(),
-            rec_print_fun()) -> chars() | unicode_chars().
+            rec_print_fun()) -> chars().
 
 print(Term, Col, Ll, D, M, RecDefFun) ->
     print(Term, Col, Ll, D, M, RecDefFun, latin1).
@@ -369,13 +367,13 @@ print_length(<<_/bitstring>>=Bin, D, _RF, Enc) ->
                     S = io_lib:write_string(List, $"), %"
 	            {[$<,$<,S,$>,$>], 4 + length(S)};
                 {false, List} when is_list(List) ->
-                    S = io_lib:write_unicode_string(List, $"), %"
+                    S = io_lib:write_string(List, $"), %"
 	            {[$<,$<,S,"/utf8>>"], 9 + length(S)};
 	        {true, true, Prefix} ->
 	            S = io_lib:write_string(Prefix, $"), %"
 	            {[$<,$<, S | "...>>"], 7 + length(S)};
 	        {false, true, Prefix} ->
-                    S = io_lib:write_unicode_string(Prefix, $"), %"
+                    S = io_lib:write_string(Prefix, $"), %"
 	            {[$<,$<, S | "/utf8...>>"], 12 + length(S)};
 	        false ->
 	            S = io_lib:write(Bin, D),
@@ -451,9 +449,9 @@ list_length_tail({_, Len}, Acc) ->
 printable_list(_L, 1, _Enc) ->
     false;
 printable_list(L, _D, latin1) ->
-    io_lib:printable_list(L);
+    io_lib:printable_latin1_list(L);
 printable_list(L, _D, _Uni) ->
-    io_lib:printable_unicode_list(L).
+    io_lib:printable_list(L).
 %% Truncated lists could break some existing code.
 % printable_list(L, D, Enc) when D >= 0 ->
 %     Len = ?CHARS * (D - 1),
@@ -538,9 +536,9 @@ printable_unicode(Bin, I, L) ->
     {I, Bin, lists:reverse(L)}.
 
 write_string(S, latin1) ->
-    io_lib:write_string(S, $"); %"
+    io_lib:write_latin1_string(S, $"); %"
 write_string(S, _Uni) ->
-    io_lib:write_unicode_string(S, $"). %"
+    io_lib:write_string(S, $"). %"
 
 %% Throw 'no_good' if the indentation exceeds half the line length
 %% unless there is room for M characters on the line.
diff --git a/lib/stdlib/src/lib.erl b/lib/stdlib/src/lib.erl
index b2ce2a5a8f..b778f3bf64 100644
--- a/lib/stdlib/src/lib.erl
+++ b/lib/stdlib/src/lib.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 1996-2012. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
 %% 
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -426,9 +426,9 @@ brackets_to_parens(S, Enc) ->
     [$(,R,$)].
 
 printable_list(latin1, As) ->
-    io_lib:printable_list(As);
+    io_lib:printable_latin1_list(As);
 printable_list(_, As) ->
-    io_lib:printable_unicode_list(As).
+    io_lib:printable_list(As).
 
 mfa_to_string(M, F, A) ->
     io_lib:fwrite(<<"~s/~w">>, [mf_to_string({M, F}, A), A]).
diff --git a/lib/stdlib/src/unicode.erl b/lib/stdlib/src/unicode.erl
index 8b9412fb1b..10b652cdde 100644
--- a/lib/stdlib/src/unicode.erl
+++ b/lib/stdlib/src/unicode.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 2008-2012. All Rights Reserved.
+%% Copyright Ericsson AB 2008-2013. All Rights Reserved.
 %% 
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -25,25 +25,32 @@
 
 -export_type([chardata/0, charlist/0, encoding/0, external_chardata/0,
               external_charlist/0, latin1_chardata/0,
-              latin1_charlist/0, unicode_binary/0, unicode_char/0]).
+              latin1_charlist/0, unicode_binary/0]).
 
 -type encoding()  :: 'latin1' | 'unicode' | 'utf8'
                    | 'utf16' | {'utf16', endian()}
                    | 'utf32' | {'utf32', endian()}.
 -type endian()    :: 'big' | 'little'.
 -type unicode_binary() :: binary().
--type unicode_char() :: non_neg_integer().
--type charlist() :: [unicode_char() | unicode_binary() | charlist()].
+-type charlist() ::
+        maybe_improper_list(char() | unicode_binary() | charlist(),
+                            unicode_binary() | nil()).
 -type chardata() :: charlist() | unicode_binary().
 -type external_unicode_binary() :: binary().
 -type external_chardata() :: external_charlist() | external_unicode_binary().
--type external_charlist() :: [unicode_char() | external_unicode_binary()
-                              | external_charlist()].
+-type external_charlist() ::
+        maybe_improper_list(char() |
+                              external_unicode_binary() |
+                              external_charlist(),
+                            external_unicode_binary() | nil()).
 -type latin1_binary() :: binary().
 -type latin1_char() :: byte().
 -type latin1_chardata() :: latin1_charlist() | latin1_binary().
--type latin1_charlist() :: [latin1_char() | latin1_binary()
-                            | latin1_charlist()].
+-type latin1_charlist() ::
+        maybe_improper_list(latin1_char() |
+                              latin1_binary() |
+                              latin1_charlist(),
+                            latin1_binary() | nil()).
 
 %%% BIFs
 %%%
diff --git a/lib/stdlib/test/io_SUITE.erl b/lib/stdlib/test/io_SUITE.erl
index 521d7255ea..4d2b53b265 100644
--- a/lib/stdlib/test/io_SUITE.erl
+++ b/lib/stdlib/test/io_SUITE.erl
@@ -2051,15 +2051,15 @@ otp_10302(Suite) when is_list(Suite) ->
     "<<228,...>>" = fmt("~tP", [<<"äppl">>, 2]),
 
     Chars = lists:seq(0, 512), % just a few...
-    [] = [C || C <- Chars, S <- io_lib:write_unicode_char_as_latin1(C),
+    [] = [C || C <- Chars, S <- io_lib:write_char_as_latin1(C),
                not is_latin1(S)],
-    L1 = [S || C <- Chars, S <- io_lib:write_unicode_char(C),
+    L1 = [S || C <- Chars, S <- io_lib:write_char(C),
                not is_latin1(S)],
     L1 = lists:seq(256, 512),
 
-    [] = [C || C <- Chars, S <- io_lib:write_unicode_string_as_latin1([C]),
+    [] = [C || C <- Chars, S <- io_lib:write_string_as_latin1([C]),
                not is_latin1(S)],
-    L2 = [S || C <- Chars, S <- io_lib:write_unicode_string([C]),
+    L2 = [S || C <- Chars, S <- io_lib:write_string([C]),
                not is_latin1(S)],
     L2 = lists:seq(256, 512),
 
diff --git a/lib/syntax_tools/src/erl_syntax.erl b/lib/syntax_tools/src/erl_syntax.erl
index 41a1708925..bdb2b5bcd7 100644
--- a/lib/syntax_tools/src/erl_syntax.erl
+++ b/lib/syntax_tools/src/erl_syntax.erl
@@ -1700,11 +1700,11 @@ char_literal(Node) ->
 -spec char_literal(syntaxTree(), encoding()) -> nonempty_string().
 
 char_literal(Node, unicode) ->
-    io_lib:write_unicode_char(char_value(Node));
+    io_lib:write_char(char_value(Node));
 char_literal(Node, utf8) ->
-    io_lib:write_unicode_char(char_value(Node));
+    io_lib:write_char(char_value(Node));
 char_literal(Node, latin1) ->
-    io_lib:write_unicode_char_as_latin1(char_value(Node)).
+    io_lib:write_char_as_latin1(char_value(Node)).
 
 
 %% =====================================================================
@@ -1801,11 +1801,11 @@ string_literal(Node) ->
 -spec string_literal(syntaxTree(), encoding()) -> nonempty_string().
 
 string_literal(Node, utf8) ->
-    io_lib:write_unicode_string(string_value(Node));
+    io_lib:write_string(string_value(Node));
 string_literal(Node, unicode) ->
-    io_lib:write_unicode_string(string_value(Node));
+    io_lib:write_string(string_value(Node));
 string_literal(Node, latin1) ->
-    io_lib:write_unicode_string_as_latin1(string_value(Node)).
+    io_lib:write_string_as_latin1(string_value(Node)).
 
 
 %% =====================================================================