[antlr-interest] Why is Filter thwarting me?

[alan brown]

Thanks for the concise clarification.  You can't beat a good active
newsgroup where blocks get unblocked at midnight! (though I presume you're
probably not in my timezone).

Cheers,

alan

On Thu, Mar 6, 2008 at 12:05 AM, Gavin Lambert <antlr at mirality.co.nz> wrote:

> At 20:54 6/03/2008, alan brown wrote:
> >Hmmmm.  I was unaware that grammars and lexers are frequently
> >split into different files.  It seems that putting the lexer in
> >its own file is no problem, but when I put the parser in its own
> >file it complains (in red in intellij) that it can't find any of
> >the tokens my rule is referring to.
> >
> >Is there some sort of #include that enables my parser to know
> >where it's looking for the tokens or should I consider the red
> >squiggles under all my token names as decoration?  :)
>
> lexer grammar foo;
> options { filter=true; }
> ...
>
> parser grammar bar;
> options { tokenVocab=foo; }
> ...
>
> See: <http://www.antlr.org/wiki/display/ANTLR3/Grammar+options>
>
> >Also, I'm confused about your explanation (though it does seem to
> >help).  If filter=true is only a lexer rule then why should it be
> >a problem defining it in a hybrid (lexer/parser) grammar
> >file?  Surely, as a lexer rule it should only affect the lexer.
>
> Because the point of hybrid grammars is to let you introduce
> additional tokens in parser rules (which get autogenerated into
> lexer rules), and one of the points of filter mode is to have a
> specific author-defined ordering of lexer rules.  The two goals
> conflict.
>
>
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