[antlr-interest] Fwd: need help with predicates

[Alexandre Porcelli]

Hi Andy and All..

 As you are working with visual basic... I think you could create
something like it:

expression //just for this sample
        :       data_reference
        |       LITERAL
        ;

data_reference
        :       IDENTIFIER
        |       IDENTIFIER '!' IDENTIFIER
        |       IDENTIFIER '!' '[' expression ']'
        |       IDENTIFIER '(' expression ')'
        ;

LITERAL //With scape logic
        :       '"'
        {
                if (input.LA(1) == '"' && input.LA(2) == '"'){
                        matchAny();
                        matchAny();
                }
        }
        (options {greedy=false;} : .
        {
                if (input.LA(1) == '"' && input.LA(2) == '"'){
                        matchAny();
                        matchAny();
                }
        }
        )* '"'
        ;

IDENTIFIER
        :       LETTER (LETTER|DIGIT|'_')* DATA_TYPE?
        ;

fragment
DATA_TYPE
        :       '%'|'#'|'$'|'&'|'@'
        ;

fragment
LETTER
        :       'a'..'z' | '\u0080'..'\ufffe'
        ;

fragment
DIGIT
        :       '0'..'9'
        ;

wdyt?

Best Regards,
Alexandre Porcelli

On 8/9/07, Richard Clark <rdclark at gmail.com> wrote:
> The usual answer to dealing with context-dependant elements is to move
> the decision from the lexer into the parser.
>
> You might do this:
>
> identifier: (ID_FRAGMENT '!' ID_FRAGMENT) => ID_FRAGMENT '!' ID_FRAGMENT
>              | ID_FRAGMENT
>              /* You still have to deal with the other suffixes */
>              ;
>
> ID_FRAGMENT: LETTER (LETTER| DECIMAL_LITERAL)* ;
>
>  ...Richard
>