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<H1>erl_pp</H1>
</CENTER>
<H3>MODULE</H3>
<DIV CLASS=REFBODY>
erl_pp
</DIV>
<H3>MODULE SUMMARY</H3>
<DIV CLASS=REFBODY>
The Erlang Pretty Printer
</DIV>
<H3>DESCRIPTION</H3>
<DIV CLASS=REFBODY>
<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>All functions can have an optional argument which specifies a hook
that is called if an attempt is made to print an unknown form.
</DIV>
<H3>EXPORTS</H3>
<P><A NAME="form/1"><STRONG><CODE>form(Form) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="form/2"><STRONG><CODE>form(Form, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Form = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Pretty prints a
<CODE>Form</CODE> which is an abstract form of a type which is
returned by <CODE>erl_parse:parse_form</CODE>.
</DIV>
<P><A NAME="attribute/1"><STRONG><CODE>attribute(Attribute) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="attribute/2"><STRONG><CODE>attribute(Attribute, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Attribute = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>The same as <CODE>form</CODE>, but only for the attribute
<CODE>Attribute</CODE>.
</DIV>
<P><A NAME="function/1"><STRONG><CODE>function(Function) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="function/2"><STRONG><CODE>function(Function, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Function = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>The same as <CODE>form</CODE>, but only for the function
<CODE>Function</CODE>.
</DIV>
<P><A NAME="guard/1"><STRONG><CODE>guard(Guard) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="guard/2"><STRONG><CODE>guard(Guard, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Form = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>The same as <CODE>form</CODE>, but only for the guard test
<CODE>Guard</CODE>.
</DIV>
<P><A NAME="exprs/1"><STRONG><CODE>exprs(Expressions) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="exprs/2"><STRONG><CODE>exprs(Expressions, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="exprs/3"><STRONG><CODE>exprs(Expressions, Indent, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Expressions = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>Indent = integer()</CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>The same as <CODE>form</CODE>, but only for the sequence of
expressions in <CODE>Expressions</CODE>.
</DIV>
<P><A NAME="expr/1"><STRONG><CODE>expr(Expression) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="expr/2"><STRONG><CODE>expr(Expression, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="expr/3"><STRONG><CODE>expr(Expression, Indent, HookFunction) -> DeepCharList</CODE></STRONG></A><BR>
<A NAME="expr/4"><STRONG><CODE>expr(Expression, Indent, Precedence, HookFunction) ->-> DeepCharList</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Expression = term()</CODE></STRONG><BR>
<STRONG><CODE>HookFunction = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>Indent = integer()</CODE></STRONG><BR>
<STRONG><CODE>Precedence = </CODE></STRONG><BR>
<STRONG><CODE>DeepCharList = [char()|DeepCharList]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>This function prints one expression. It is useful for implementing hooks (see below).
</DIV>
<H3>Unknown Expression Hooks</H3>
<DIV CLASS=REFBODY>
<P>The optional argument <CODE>HookFunction</CODE>, 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>
<DL>
<DT>
<CODE>Function</CODE>
</DT>
<DD>
The hook function is called by:<BR>
<PRE>
Function(Expr,
CurrentIndentation,
CurrentPrecedence,
HookFunction)
</PRE>
</DD>
<DT>
<CODE>none</CODE>
</DT>
<DD>
There is no hook function<BR>
</DD>
</DL>
<P>The called hook function should return a (possibly deep) list
of characters. <CODE>expr/4</CODE> is useful in a hook.
<P>If <CODE>CurrentIndentation</CODE> is negative, there will be no line
breaks and only a space is used as a separator.
</DIV>
<H3>Bugs</H3>
<DIV CLASS=REFBODY>
<P>It should be possible to have hook functions for unknown forms
at places other than expressions.
</DIV>
<H3>See Also</H3>
<DIV CLASS=REFBODY>
<P><A HREF="io.html">io(3)</A>,
<A HREF="erl_parse.html">erl_parse(3)</A>,
<A HREF="erl_eval.html">erl_eval(3)</A>
</DIV>
<H3>AUTHORS</H3>
<DIV CLASS=REFBODY>
Robert Virding - support@erlang.ericsson.se<BR>
</DIV>
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<SMALL>stdlib 1.14.2<BR>
Copyright © 1991-2006
<A HREF="http://www.erlang.se">Ericsson AB</A><BR>
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