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

<H3>MODULE SUMMARY</H3>
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The Erlang Token Scanner
</DIV>

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

<P>This module contains functions for tokenizing characters into
Erlang tokens.

</DIV>

<H3>EXPORTS</H3>

<P><A NAME="string/2"><STRONG><CODE>string(CharList,StartLine]) -&#62; {ok, Tokens, EndLine} | Error</CODE></STRONG></A><BR>
<A NAME="string/1"><STRONG><CODE>string(CharList) -&#62; {ok, Tokens, EndLine} | Error</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<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>

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<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.

</DIV>

<P><A NAME="tokens/3"><STRONG><CODE>tokens(Continuation, CharList, StartLine) -&#62;Return</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<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>

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<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>

</DIV>

<P><A NAME="reserved_word/1"><STRONG><CODE>reserved_word(Atom) -&#62; bool()</CODE></STRONG></A><BR>

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<P>Returns <CODE>true</CODE> if <CODE>Atom</CODE> is an Erlang reserved
word, otherwise <CODE>false</CODE>.

</DIV>

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

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>ErrorDescriptor = errordesc()</CODE></STRONG><BR>

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<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).

</DIV>

<H3>Error Information</H3>
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<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>

</DIV>

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

<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.


</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>

</DIV>

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

</DIV>
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