[antlr-interest] ANTLR 2: single-line comment lexing with no newline

[Matt Benson]

--- Gavin Lambert <antlr at mirality.co.nz> wrote:

> At 08:03 9/03/2007, Matt Benson wrote:
>  >I have the following lexer rules (can't remember
> how
>  >much of them are copied vs. original).  My intent
> is,
>  >as implied by my subject line, to recognize a
>  >single-line comment at the end of the file--an old
>  >problem.  I am seeing ANTLR spin forever when it
> hits
>  >the comment with these rules.  Can anyone see what
>  >might be wrong?  Rules follow.
> [...]
>  >// Single-line comments
>  >SL_COMMENT
>  >	:	"//"
>  >		(~('\n'|'\r'))* (NL)?
>  >		{$setType(Token.SKIP);}
>  >	;
> 
> My first thought is that since you've made NL
> optional and 
> permitted just about anything before it, it's doing
> the greediest 
> possible match first (the entire file) and working
> its way back, 
> spinning for ages.
> 
> Try either making NL not optional, or using NL|EOF
> (also not 
> optional).
> 
> 
Actually, I tried ( NL | EOF ) but I get the error
that there is no EOF token.  That would probably work
better in a parser rule.  How can I recognize EOF as a
"character" in a lexer?

Thanks,
Matt


 
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