[antlr-interest] Token stream filter

[Ric Klaren]

On Thu, Jun 03, 2004 at 09:24:07AM +0100, Anthony Youngman wrote:
> Thanks. Actually, Monty's solution should work ...

It looks a lot simpler ;)

> but seeing as you seem to know these things, taking this line from my
> original post

I'm only theorizing ;)

> 	(id:IDENT {if text != "REM" throw tokenmatchexception}|"*"|"!")
>
> which is the exception I need to throw here?

If you're trying to make the rule work inside a ( )=>( ) construct then it
should be something RecognitionException like (or derived of it)

> So - I can feed the lexer output into my deremer parser - and I can then
> feed the output from that into my main parser?

If you follow Monty's framework you should be ok I guess.

> And if I have a rule like
>
> commentst : (EOL | SEMI) ("*" | "!")! (~(EOL)*)! ;
>
> it will then eat everything between the initial eol/semi and final eol,
> but it will let those two tokens through to the next parser?

If you write the code in nextToken to do that it will. The ! operator
controls treebuilding it's not the lexer's ! operator. At least I was under
the impression you wanted to use a parser to do the filtering not a lexer
in front of your original lexer.

Cheers,

Ric
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