Réf. : RE: [antlr-interest] Warning/ambiguity suppression

[loic.lefevre at bnpparibas.com]

Indeed, the grammar was like that at the beginning.

After the changes, I had to change the primaryExpression rule to:

// the basic element of an expression
primaryExpression
      :   !"true" { #primaryExpression=#[TRUE,"TRUE"]; }
        | !"false" { #primaryExpression=#[FALSE,"FALSE"]; }
                  | constant
                  | identPrimary
        | LPAREN! logicalOrExpression RPAREN!
      ;

And now everything works perfectly.

Thanks Nigel and Oli.
Loïc




Internet
nbsherid at secsme.org.au@antlr.org - 22/07/2005 14:21


Envoyé par :      antlr-interest-bounces at antlr.org



Pour : antlr-interest

cc :


Objet :     RE: [antlr-interest] Warning/ambiguity suppression



> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Olivier Dragon
> Sent: Friday, 22 July 2005 10:06 PM
> To: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Warning/ambiguity suppression
>
> You could use predicates and match a non-identifier character after the
> word (you could have a variable named trueThat or falseData).
>
> TRUE:
>            ("true" ~(IDENTCHAR))=> "true" ;
> FALSE:
>            ("false" ~(IDENTCHAR))=> "false" ;
>
> protected IDENTCHAR:
>            ('a'..'z'|'A'..'Z'|'0'..'9'|'_') ;
>

Alternatively, you could make "true" and "false" literals to be tested, by
moving them out of the lexer and into the parser.

Remove these from lexer:

TRUE:"true";
FALSE:"false";


And modify this in parser:

primaryExpression
             :           "true"
               | "false"
    | constant
    |        identPrimary
               |         LPAREN! logicalOrExpression RPAREN!
             ;


They will be treated as IDENT tokens until the test for literals, and then
converted to "literal_TRUE" and "literal_FALSE" tokens. Consequently, you
might need to modify the tokens{} section of your parser accordingly, since
you are generating a Heterogeneous AST.

Nigel

--
Nigel Sheridan-Smith
PhD research student

Faculty of Engineering
University of Technology, Sydney
Phone: 02 9514 7946
Fax: 02 9514 2435





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