[antlr-interest] distinquishing single from multiple characte rs

[mzukowski at bco.com]

I think this is covered in the lexer docs but I don't have the reference
handy, so here's how you combine the two rules which are ambiguous because
they have the same prefix.  This is a problem for lexers only because of the
synthesized nextToken() rule:

 END_TOKEN: ( options {greedy=true;} "." (GRAPHIC_CHAR
{$setType(GRAPHIC_TOKEN);})* );

Monty

> -----Original Message-----
> From: Michael Labhard [mailto:ince at pacifier.com]
> Sent: Friday, February 01, 2002 1:05 AM
> To: antlr-interest at yahoogroups.com
> Subject: [antlr-interest] distinquishing single from multiple 
> characters
> 
> 
> Question on Lexer.  The grammar (prolog) has two types of 
> tokens both of 
> which contain the same characters.  Specifically the "." may 
> appear alone as 
> the end token or it may appear together with other characters 
> such as "$&%", 
> etc. as a graphic token.  However, the rules:
> 
> GRAPHIC_TOKEN: ( options {greedy=true;} "." (GRAPHIC_CHAR)+ );
> 
> END_TOKEN: ".";
> 
> are flagged as ambiguous, even though in the graphic token 
> case there must be 
> at least 2 characters.  What is the best way to resolve such 
> an ambiguity?  
> Thanks.
> 
> -- Michael
> 
>  
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