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<H1>erl_parse</H1>
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<H3>MODULE</H3>
<DIV CLASS=REFBODY>
erl_parse
</DIV>

<H3>MODULE SUMMARY</H3>
<DIV CLASS=REFBODY>
The Erlang Parser
</DIV>

<H3>DESCRIPTION</H3>
<DIV CLASS=REFBODY>

<P>This module is the basic Erlang parser which converts tokens into
the abstract form of either forms (i.e., top-level constructs),
expressions, or terms. The Abstract Format is described in the ERTS
User's Guide.
Note that a token list must end with the <STRONG>dot</STRONG> token in order
to be acceptable to the parse functions (see erl_scan).

</DIV>

<H3>EXPORTS</H3>

<P><A NAME="parse_form/1"><STRONG><CODE>parse_form(Tokens) -&#62; {ok, AbsForm} | {error, ErrorInfo}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Tokens = [Token]</CODE></STRONG><BR>
<STRONG><CODE>Token = {Tag,Line} | {Tag,Line,term()}</CODE></STRONG><BR>
<STRONG><CODE>Tag = atom()</CODE></STRONG><BR>
<STRONG><CODE>AbsForm = term()</CODE></STRONG><BR>
<STRONG><CODE>ErrorInfo = see section Error Information below.</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function parses <CODE>Tokens</CODE> as if it were a form. It returns:

<P>
<DL>

<DT>
<CODE>{ok, AbsForm}</CODE>
</DT>

<DD>
 The parsing was successful. <CODE>AbsForm</CODE> is the
         abstract form of the parsed form.
<BR>

</DD>

<DT>
<CODE>{error, ErrorInfo}</CODE>
</DT>

<DD>
An error occurred.<BR>

</DD>

</DL>

</DIV>

<P><A NAME="parse_exprs/1"><STRONG><CODE>parse_exprs(Tokens) -&#62; {ok, Expr_list} | {error, ErrorInfo}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Tokens = [Token]</CODE></STRONG><BR>
<STRONG><CODE>Token = {Tag,Line} | {Tag,Line,term()}</CODE></STRONG><BR>
<STRONG><CODE>Tag = atom()</CODE></STRONG><BR>
<STRONG><CODE>Expr_list = [AbsExpr]</CODE></STRONG><BR>
<STRONG><CODE>AbsExpr = term()</CODE></STRONG><BR>
<STRONG><CODE>ErrorInfo = see section Error Information below.</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function parses <CODE>Tokens</CODE> as if it were a list of expressions. It returns:

<P>
<DL>

<DT>
<CODE>{ok, Expr_list}</CODE>
</DT>

<DD>
 The parsing was successful. <CODE>Expr_list</CODE> is a
         list of the abstract forms of the parsed expressions.
<BR>

</DD>

<DT>
<CODE>{error, ErrorInfo}</CODE>
</DT>

<DD>
An error occurred.<BR>

</DD>

</DL>

</DIV>

<P><A NAME="parse_term/1"><STRONG><CODE>parse_term(Tokens) -&#62; {ok, Term} | {error, ErrorInfo}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Tokens = [Token]</CODE></STRONG><BR>
<STRONG><CODE>Token = {Tag,Line} | {Tag,Line,term()}</CODE></STRONG><BR>
<STRONG><CODE>Tag = atom()</CODE></STRONG><BR>
<STRONG><CODE>Term = term()</CODE></STRONG><BR>
<STRONG><CODE>ErrorInfo = see section Error Information below.</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function parses <CODE>Tokens</CODE> as if it were a term. It returns:

<P>
<DL>

<DT>
<CODE>{ok, Term}</CODE>
</DT>

<DD>
 The parsing was successful. <CODE>Term</CODE> is
         the Erlang term corresponding to the token list.
<BR>

</DD>

<DT>
<CODE>{error, ErrorInfo}</CODE>
</DT>

<DD>
An error occurred.<BR>


</DD>

</DL>

</DIV>

<P><A NAME="format_error/1"><STRONG><CODE>format_error(ErrorDescriptor) -&#62; Chars</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>ErrorDescriptor = errordesc()</CODE></STRONG><BR>
<STRONG><CODE>Chars = [char() | Chars]</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Uses an <CODE>ErrorDescriptor</CODE> and returns a string
which describes the error. This function is usually called
implicitly when an <CODE>ErrorInfo</CODE> structure is processed
(see below).

</DIV>

<P><A NAME="tokens/1"><STRONG><CODE>tokens(AbsTerm) -&#62; Tokens</CODE></STRONG></A><BR>
<A NAME="tokens/2"><STRONG><CODE>tokens(AbsTerm, MoreTokens) -&#62; Tokens</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Tokens = MoreTokens = [Token]</CODE></STRONG><BR>
<STRONG><CODE>Token = {Tag,Line} | {Tag,Line,term()}</CODE></STRONG><BR>
<STRONG><CODE>Tag = atom()</CODE></STRONG><BR>
<STRONG><CODE>AbsTerm = term()</CODE></STRONG><BR>
<STRONG><CODE>ErrorInfo = see section Error Information below.</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function generates a list of tokens representing the abstract
        form <CODE>AbsTerm</CODE> of an expression. Optionally, it appends
        <CODE>Moretokens</CODE>.

</DIV>

<P><A NAME="normalise/1"><STRONG><CODE>normalise(AbsTerm) -&#62; Data</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>AbsTerm = Data = term()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Converts the abstract form <CODE>AbsTerm</CODE> of a term into a
conventional Erlang data structure (i.e., the term itself).
         This is the inverse of <CODE>abstract/1</CODE>.

</DIV>

<P><A NAME="abstract/1"><STRONG><CODE>abstract(Data) -&#62; AbsTerm</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Data = AbsTerm = term()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Converts the Erlang data structure <CODE>Data</CODE> into an
abstract form of type <CODE>AbsTerm</CODE>. This is the inverse of
         <CODE>normalise/1</CODE>.

</DIV>

<H3>Error Information</H3>
<DIV CLASS=REFBODY>

<P>The <CODE>ErrorInfo</CODE> mentioned above is the standard
<CODE>ErrorInfo</CODE> structure which is returned from all IO
modules. It has the format:


<PRE>
    {ErrorLine, Module, ErrorDescriptor}
</PRE>

<P>A string which describes the error is obtained with the following call:


<PRE>
apply(Module, format_error, ErrorDescriptor)
</PRE>

</DIV>

<H3>See Also</H3>
<DIV CLASS=REFBODY>

<P><A HREF="io.html">io(3)</A>,
<A HREF="erl_scan.html">erl_scan(3)</A>,
ERTS User's Guide

</DIV>

<H3>AUTHORS</H3>
<DIV CLASS=REFBODY>
Robert Virding - support@erlang.ericsson.se<BR>

</DIV>
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