[antlr-interest] AntLR Bug solved

[mzukowski at bco.com]

What are you expecting when you see ".."?  You will get one token of type
GRAPHIC_TOKEN, is that what you want?

Monty

> -----Original Message-----
> From: Michael Labhard [mailto:ince at pacifier.com]
> Sent: Tuesday, February 05, 2002 1:53 AM
> To: AntLR Interest
> Subject: [antlr-interest] AntLR Bug solved
> 
> 
> All:
> 
> 	The following lexer file compiles without warnings and 
> does distinguish a 
> single END_CHAR from an END_CHAR followed by other GRAPHIC_TOKENS.
> 
> class L extends Lexer;
> options { k=2; }
> 
> NAME_TOKEN
>   : GRAPHIC_TOKEN
>   ;
> 
> END_TOKEN: 
>     END_CHAR 
>     (
> 	(END_CHAR | GRAPHIC_TOKEN_CHAR)+ 
> 	{$setType(GRAPHIC_TOKEN);}
>     )
>     ;
> 
> protected 
> GRAPHIC_TOKEN
>     :
>     GRAPHIC_TOKEN_CHAR 
>     (END_CHAR | GRAPHIC_TOKEN_CHAR)* 
>     ;
> 
> protected 
> GRAPHIC_TOKEN_CHAR
>   : GRAPHIC_CHAR | BACKSLASH_CHAR
>   ;
> 
> protected 
> GRAPHIC_CHAR
>   : ( options {greedy=true;} : 
>     '#'|'$'|'&'|'*'|'+'|'/'
>     |':'|'<'|'='|'>'|'?'|'@'|'^'|'~'
>     );
> 
> protected 
> END_CHAR: '.' ;
> 
> protected 
> BACKSLASH_CHAR: '\\' ;
> 
> 	From this experience I come to understand 
> "left-factoring" to mean, in 
> practice, move all cases of the left-hand part of the token 
> into a single 
> rule.  That was the trick here.  The rule END_TOKEN handles 
> all cases in 
> which END_CHAR is the first character.  Previously the 
> GRAPHIC_TOKEN rule was 
> also attempting to handle this condition, along with the 
> END_TOKEN rule.   
> Thanks to all for your encouragement.  It was very instructive.
> 
> -- Michael
> 
> 
>  
> 
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