[antlr-interest] semantic predicate affects nothing
Markus Kuhla
bace.spam at gmx.net
Sun Jun 17 22:52:56 PDT 2007
Oh yes, I tried this too, but does not changes the behavior. The block is still recognized as an inline element and throw the exception at the newline after '((('.
I didn't understand the meaning of the '|' so I omitted it ;)
Best regards!
Markus
> You're missing an '|' after the {false}? . That syntactic predict is
> always
> going to fail without it.
>
> text_paragr : (OPEN ((NEWLINE)=>{false}? |)) => text_line+;
>
>
>
> ----- Original Message -----
> From: "Markus Kuhla" <bace.spam at gmx.net>
> To: <antlr-interest at antlr.org>
> Sent: Sunday, June 17, 2007 8:31 PM
> Subject: [antlr-interest] semantic predicate affects nothing
>
>
> > Hi guys,
> >
> > I try to use the semantic predicate "match alpha if not followed by
> beta"
> > from http://www.antlr.org/blog/antlr3/lookahead.tml (section May 11,
> > 2006).
> >
> > I want to distinguish between an inline element in a text paragraph and
> > block (an extra paragraph). The block is indicated by '(((\n', in inline
> > is no newline allowed. Before a block begins, the text paragraph has to
> > end (out of the +loop).
> >
> > The problem is, that the parser does not change its behavior, it always
> > matches the block as an inline element and throws an exception at the
> > newline.
> >
> > I wrote the v3 grammar as short as possible to show this:
> >
> > page : paragraph *;
> > paragraph : text_parag | block;
> > text_paragr : (OPEN ((NEWLINE)=>{false}? )) => text_line+;
> > text_line : (TEXT | inline)+ NEWLINE;
> > inline : OPEN text CLOSE;
> > block : OPEN NEWLINE TEXT* NEWLINE CLOSE NEWLINE;
> > text : ANY *;
> >
> > OPEN : '(((';
> > CLOSE : ')))';
> > NEWLINE : '\r\n';
> > ANY : .;
> >
> >
> > Thanks for any assistance!
> > Best,
> > Markus
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