[antlr-interest] behaviour of lexer

[Bart Kiers]

On Tue, Mar 2, 2010 at 5:25 PM, Philippe Frankson <
Philippe.Frankson at frsglobal.com> wrote:

> ...
> @int('444') is a function converting a string into integer.
> If I don't have parentheses, then it is not a function, it is only a column
> name. Ex.: @test, @integer, @in, ....
>
> Here is a part of lexer rules:
>
> fragment DIGIT  : ('0'..'9');
> fragment ALPHA  : ('a'..'z'|'A'..'Z'|'_');
>
> OB              : '(';
> INTTOKEN        : ('@int' OB)=> '@int'; // so I check if there is an open
> parenthesis to return INTTOKEN.
> AT              : '@';
> NAME            : ALPHA (ALPHA | DIGIT)*;   ...
>

Why not just include the OB in your lexer rule?
Something like this:

INT_METHOD      : AT 'int' OB; // or: AT 'int' OB STRING CB;
COLUMN          : AT NAME;

OB              : '(';
AT              : '@';
NAME            : ALPHA (ALPHA | DIGIT)*;

fragment DIGIT  : ('0'..'9');
fragment ALPHA  : ('a'..'z'|'A'..'Z'|'_');

and because lexer rules are matched from top to bottom, '@int' will be
matched as 'AT NAME'.

Regards,

Bart.