[antlr-interest] Lexer matching non-matching rule
Micha
micha-1 at fantasymail.de
Sun May 17 04:56:31 PDT 2009
On Sunday 17 May 2009 13:22:37 Jesper Larsson wrote:
> On Sun, 2009-05-17 at 12:48 +0200, Micha wrote:
> > On Sunday 17 May 2009 11:01:36 Jesper Larsson wrote:
> > > Not always so easy, however. My original example was, even more
> > > simplified, something like this:
> > >
> > > FOO: 'foo';
> > > BAR: 'bar';
> > > FOOZ: 'foo'* 'z';
> >
> > that works with the method mentioned earlier:
>
> Hm, as far as I can tell your variant has exactly the same problems as
> mine. The following grammar, incorporating the trick from yours, can
> match "foobar" as FOO BAR but fails on "foofoobar":
*Argh* you need the synpred again:
> ============================================
> grammar Y;
> options { output=AST; }
start : ( FOO { System.out.println("foo, ");}
| BAR { System.out.println("bar, ");}
| FOOZ { System.out.println("FOOZ, ");} )* EOF;
WS : (' ' | '\t' | '\n')+ { skip(); };
fragment
FOO : ;
BAR : 'bar';
fragment FOOZ
: ;
fragment FOOZ_LA
: 'foo'* 'z';
FOO_OR_FOOZ
: (
'foo' { $type = FOO; }
((FOOZ_LA) => FOOZ_LA { $type = FOOZ;})?
)
| 'z' { $type = FOOZ;};
Michael
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