[antlr-interest] Problem with lexical nondeterminism - ANTLR 2.7.7

[Harald Mueller]

Just off my head, you could write something like (I did not check the syntax at all)

NUMBER
    : DIGIT+ 
      ( COMMA CHAR CHAR { $type = APAC_NUMERIC_TICKER; }
      |                 // remains a NUMBER
      )

- only ANTLR 3 can look that far ahead ... (and you dont need so many parentheses).

Regards
Harald

-------- Original-Nachricht --------
> Datum: Thu, 3 Jan 2008 13:24:35 +0000
> Von: clive.i.hill at jpmorgan.com
> An: antlr-interest at antlr.org
> Betreff: [antlr-interest] Problem with lexical nondeterminism - ANTLR 2.7.7

> Hi,
> 
> I get the following warning when building my lexer from stragegy.g:
> 
> /Grammar/strategy.g: warning:lexical nondeterminism between rules NUMBER 
> and APAC_NUMERIC_TICKER upon
> ./Grammar/strategy.g:     k==1:'0'..'9'
> ./Grammar/strategy.g:     k==2:'0'..'9'
> ./Grammar/strategy.g:     k==3:'0'..'9'
> ./Grammar/strategy.g:     k==4:'0'..'9'
> 
> Passing the following string fails:
> 
> "spx dec 1350 c 43 44"
> 
> As it takes 1350 to be an APAC_NUMERIC_TICKER when I it to be considered 
> to be a NUMBER.  Interestingly, the following works:
> 
> "spx dec 135 c 43 44"
> 
> My definition for the lexer rule is:
> 
> APAC_NUMERIC_TICKER
>     
>     ;
> 
> I want this to only be used if a string entered "has at least one DIGIT 
> and is followed by a COMMA then two CHARs".  This is clearly not the case 
> for the string 1350 - and yet it matches,  and then throws the exception:
> 
> 
> antlr.TokenStreamRecognitionException: expecting ',', found ' '
> 
> 
> Can anyone suggest a way to only match this rule if it is in the correct 
> format ((DIGIT)+ (COMMA) (CHAR) (CHAR)) ?
> 
> Thanks in advance,
> 
> Clive
> 
> 
> 
> Attached is my grammar file.
> 
> 
> 
> 
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