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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
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The R13B03 release.OTP_R13B03
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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE erlref SYSTEM "erlref.dtd">
+
+<erlref>
+ <header>
+ <copyright>
+ <year>1996</year>
+ <year>2007</year>
+ <holder>Ericsson AB, All Rights Reserved</holder>
+ </copyright>
+ <legalnotice>
+ 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
+ compliance with the License. You should have received a copy of the
+ Erlang Public License along with this software. If not, it can be
+ retrieved online at http://www.erlang.org/.
+
+ Software distributed under the License is distributed on an "AS IS"
+ basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ the License for the specific language governing rights and limitations
+ under the License.
+
+ The Initial Developer of the Original Code is Ericsson AB.
+ </legalnotice>
+
+ <title>erl_pp</title>
+ <prepared>Robert Virding</prepared>
+ <responsible>Bjarne D&auml;cker</responsible>
+ <docno>1</docno>
+ <approved>Bjarne D&auml;cker</approved>
+ <checked></checked>
+ <date>97-01-24</date>
+ <rev>B</rev>
+ <file>erl_pp.sgml</file>
+ </header>
+ <module>erl_pp</module>
+ <modulesummary>The Erlang Pretty Printer</modulesummary>
+ <description>
+ <p>The functions in this module are used to generate
+ aesthetically attractive representations of abstract
+ forms, which are suitable for printing. All functions return (possibly deep)
+ lists of characters and generate an error if the form is wrong.</p>
+ <p>All functions can have an optional argument which specifies a hook
+ that is called if an attempt is made to print an unknown form.</p>
+ </description>
+ <funcs>
+ <func>
+ <name>form(Form) -> DeepCharList</name>
+ <name>form(Form, HookFunction) -> DeepCharList</name>
+ <fsummary>Pretty print a form</fsummary>
+ <type>
+ <v>Form = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>Pretty prints a
+ <c>Form</c> which is an abstract form of a type which is
+ returned by <c>erl_parse:parse_form</c>.</p>
+ </desc>
+ </func>
+ <func>
+ <name>attribute(Attribute) -> DeepCharList</name>
+ <name>attribute(Attribute, HookFunction) -> DeepCharList</name>
+ <fsummary>Pretty print an attribute</fsummary>
+ <type>
+ <v>Attribute = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>The same as <c>form</c>, but only for the attribute
+ <c>Attribute</c>.</p>
+ </desc>
+ </func>
+ <func>
+ <name>function(Function) -> DeepCharList</name>
+ <name>function(Function, HookFunction) -> DeepCharList</name>
+ <fsummary>Pretty print a function</fsummary>
+ <type>
+ <v>Function = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>The same as <c>form</c>, but only for the function
+ <c>Function</c>.</p>
+ </desc>
+ </func>
+ <func>
+ <name>guard(Guard) -> DeepCharList</name>
+ <name>guard(Guard, HookFunction) -> DeepCharList</name>
+ <fsummary>Pretty print a guard</fsummary>
+ <type>
+ <v>Form = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>The same as <c>form</c>, but only for the guard test
+ <c>Guard</c>.</p>
+ </desc>
+ </func>
+ <func>
+ <name>exprs(Expressions) -> DeepCharList</name>
+ <name>exprs(Expressions, HookFunction) -> DeepCharList</name>
+ <name>exprs(Expressions, Indent, HookFunction) -> DeepCharList</name>
+ <fsummary>Pretty print <c>Expressions</c></fsummary>
+ <type>
+ <v>Expressions = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>Indent = integer()</v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>The same as <c>form</c>, but only for the sequence of
+ expressions in <c>Expressions</c>.</p>
+ </desc>
+ </func>
+ <func>
+ <name>expr(Expression) -> DeepCharList</name>
+ <name>expr(Expression, HookFunction) -> DeepCharList</name>
+ <name>expr(Expression, Indent, HookFunction) -> DeepCharList</name>
+ <name>expr(Expression, Indent, Precedence, HookFunction) ->-> DeepCharList</name>
+ <fsummary>Pretty print one <c>Expression</c></fsummary>
+ <type>
+ <v>Expression = term()</v>
+ <v>HookFunction = see separate description below.</v>
+ <v>Indent = integer()</v>
+ <v>Precedence = </v>
+ <v>DeepCharList = [char()|DeepCharList]</v>
+ </type>
+ <desc>
+ <p>This function prints one expression. It is useful for implementing hooks (see below).</p>
+ </desc>
+ </func>
+ </funcs>
+
+ <section>
+ <title>Unknown Expression Hooks</title>
+ <p>The optional argument <c>HookFunction</c>, shown in the functions described above, defines a function which is called when an unknown form occurs where there
+ should be a valid expression. It can have the following formats:</p>
+ <taglist>
+ <tag><c>Function</c></tag>
+ <item>
+ <p>The hook function is called by:</p>
+ <code type="none">
+Function(Expr,
+ CurrentIndentation,
+ CurrentPrecedence,
+ HookFunction) </code>
+ </item>
+ <tag><c>none</c></tag>
+ <item>
+ <p>There is no hook function</p>
+ </item>
+ </taglist>
+ <p>The called hook function should return a (possibly deep) list
+ of characters. <c>expr/4</c> is useful in a hook.
+ </p>
+ <p>If <c>CurrentIndentation</c> is negative, there will be no line
+ breaks and only a space is used as a separator.</p>
+ </section>
+
+ <section>
+ <title>Bugs</title>
+ <p>It should be possible to have hook functions for unknown forms
+ at places other than expressions.</p>
+ </section>
+
+ <section>
+ <title>See Also</title>
+ <p><seealso marker="io">io(3)</seealso>,
+ <seealso marker="erl_parse">erl_parse(3)</seealso>,
+ <seealso marker="erl_eval">erl_eval(3)</seealso></p>
+ </section>
+</erlref>
+