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<HTML>
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<TITLE>erl_scan</TITLE>
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<H1>erl_scan</H1>
</CENTER>
<H3>MODULE</H3>
<UL>
erl_scan</UL>
<H3>MODULE SUMMARY</H3>
<UL>
The Erlang Token Scanner</UL>
<H3>DESCRIPTION</H3>
<UL>
<P>This module contains functions for tokenizing characters into
Erlang tokens.
</UL>
<H3>EXPORTS</H3>
<P><A NAME="string%2"><STRONG><CODE>string(CharList,StartLine]) -> {ok, Tokens, EndLine} | Error</CODE></STRONG></A><BR>
<A NAME="string%1"><STRONG><CODE>string(CharList) -> {ok, Tokens, EndLine} | Error</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>CharList = string()</CODE></STRONG><BR>
<STRONG><CODE>StartLine = EndLine = Line = integer()</CODE></STRONG><BR>
<STRONG><CODE>Tokens = [{atom(),Line}|{atom(),Line,term()}]</CODE></STRONG><BR>
<STRONG><CODE>Error = {error, ErrorInfo, EndLine}</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Takes the list of characters <CODE>CharList</CODE> and tries to scan (tokenize) them. Returns <CODE>{ok, Tokens, EndLine}</CODE>, where <CODE>Tokens</CODE> are the Erlang tokens
from <CODE>CharList</CODE>. <CODE>EndLine</CODE> is the last line where a token was found.
<P><CODE>StartLine</CODE> indicates the initial line when scanning starts. <CODE>string/1</CODE> is equivalent to <CODE>string(CharList,1)</CODE>.
<P><CODE>{error, ErrorInfo, EndLine}</CODE> is returned if an error occurs.
<CODE>EndLine</CODE> indicates where the error occurred.
</UL>
<P><A NAME="tokens%3"><STRONG><CODE>tokens(Continuation, CharList, StartLine) ->Return</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Return = {done, Result, LeftOverChars} | {more, Continuation}</CODE></STRONG><BR>
<STRONG><CODE>Continuation = [] | string()</CODE></STRONG><BR>
<STRONG><CODE>CharList = string()</CODE></STRONG><BR>
<STRONG><CODE>StartLine = EndLine = integer()</CODE></STRONG><BR>
<STRONG><CODE>Result = {ok, Tokens, EndLine} | {eof, EndLine}</CODE></STRONG><BR>
<STRONG><CODE>Tokens = [{atom(),Line}|{atom(),Line,term()}]</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>This is the re-entrant scanner which scans characters until
a <STRONG>dot</STRONG> ('.' whitespace) has been reached. It returns:
<P><DL>
<DT><CODE>{done, Result, LeftOverChars}</CODE></DT>
<DD> This return indicates that there is sufficient input data to get an
input. <CODE>Result</CODE> is:
<BR>
<BR>
<DL>
<DT><CODE>{ok, Tokens, EndLine}</CODE></DT>
<DD> The scanning was successful. <CODE>Tokens</CODE> is the
list of tokens including <STRONG>dot</STRONG>.
<BR>
</DD>
<DT><CODE>{eof, EndLine}</CODE></DT>
<DD> End of file was encountered before any more tokens.
<BR>
</DD>
<DT><CODE>{error, ErrorInfo, EndLine}</CODE></DT>
<DD> An error occurred.
<BR>
</DD>
</DL>
</DD>
<DT><CODE>{more, Continuation}</CODE></DT>
<DD> More data is required for building a term.
<CODE>Continuation</CODE> must be passed in a new call to
<CODE>tokens/3</CODE> when more data is available.
<BR>
</DD>
</DL>
</UL>
<P><A NAME="reserved_word%1"><STRONG><CODE>reserved_word(Atom) -> bool()</CODE></STRONG></A><BR>
<UL>
<P>Returns <CODE>true</CODE> if <CODE>Atom</CODE> is an Erlang reserved
word, otherwise <CODE>false</CODE>.
</UL>
<P><A NAME="format_error%1"><STRONG><CODE>format_error(ErrorDescriptor) -> string() </CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>ErrorDescriptor = errordesc()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Takes an <CODE>ErrorDescriptor</CODE> and returns a string which
describes the error or warning. This function is usually
called implicitly when processing an <CODE>ErrorInfo</CODE>
structure (see below).
</UL>
<H3>Error Information</H3>
<UL>
<P>The <CODE>ErrorInfo</CODE> mentioned above is the standard
<CODE>ErrorInfo</CODE> structure which is returned from all IO
modules. It has the following 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></UL>
<H3>Notes</H3>
<UL>
<P>The continuation of the first call to the re-entrant input
functions must be <CODE>[]</CODE>. Refer to Armstrong, Virding and Williams, 'Concurrent Programming in Erlang', Chapter 13, for a complete description of how
the re-entrant input scheme works.
</UL>
<H3>See Also</H3>
<UL>
<P><A HREF="io.html">io</A>
<A HREF="erl_parse.html">erl_parse</A>
</UL>
<H3>AUTHORS</H3>
<UL>
Robert Virding - support@erlang.ericsson.se<BR>
</UL>
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<FONT SIZE=-1>stdlib 1.10<BR>
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<A HREF="http://www.erlang.se">Ericsson Utvecklings AB</A><BR>
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