[antlr-interest] (no subject)

[Imre András]

Gerald Rosenberg <gerald at certiv.net> írta: 


> At 06:39 PM 10/31/2008, =?ISO-8859-2?Q?Imre_Andr=E1s?= wrote:
> 
> >Now how can I explicitly tell that SEQUENCE is a keyword, and not a valid ID?
> 
> 
> tokens { SQ; }
> 
> ID:        { 'SEQUENCE' }=> 'SEQUENCE'  {$type = SQ}
>          | ('a'..'z'|'A'..'Z')+ ;
> it with some necessary changes (please find the current grammar below).
This compiles ok (I'm still wondering about the $type and token magic), but there is a problem with processing A ::= SEQUENCE { a, SEQUENCE, c} as input. A MismatchedTokenException occurs instead of treating SEQUENCE as an ID.
How can I tell ANTLR that 'SEQUENCE' means a list when followed by '{', otherwise it is an ID?


Thanks,
  András

--- grammar -------------------- 
grammar keyword;

tokens { SQ; }

DEFINES : '::=' ;
WS : (' '|'\t')+ {skip();} ;
SEQUENCE : 'SEQUENCE';

prog: stat+ ;

stat: assignment;

assignment : leftValue DEFINES rightValue {System.out.println($leftValue.value + "=" + $rightValue.value);};

leftValue returns [String value]: ID {$value = $ID.text;};
rightValue returns [String value]: ID {$value = $ID.text;}| sequence {$value = $sequence.value;};

sequence returns [String value]: SEQUENCE '{' e=rightValue {$value=$e.value;} (',' e=rightValue {$value += $e.value;})* '}';

ID: ( SEQUENCE )=> SEQUENCE {$type = SQ;} | ('a'..'z'|'A'..'Z')+ ;

--- end of grammar --- 
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