[antlr-interest] Re: Local lookahead depth

[Oliver Zeigermann]

--- In antlr-interest at yahoogroups.com, "lgcraymer" <lgc at m...> wrote:
> --- In antlr-interest at yahoogroups.com, Oliver Zeigermann 
> <oliver at z...> wrote:
> > Admitted, this is not a really practical example, but consider
the 
> > following grammar:
> > 
> > {
> >      int cnt = 0;
> > }
> > 
> > LANGUAGE
> >      : ( SHORTWORD ) => SHORTWORD { System.out.println("SHORT"); }
> >      | LONGWORD { System.out.println("LONG"); }
> >      ;
> > 
> > protected SHORTWORD : { cnt = 0; } ( {cnt < 1000}? '*' { cnt++; }
)
> + '#' ;
> > protected LONGWORD : { cnt = 0; } ( {cnt < 10000}? '*' { cnt++; }
)
> + '#' ;
> > 
> > It describes a language with two words:
> > 1.) SHORTWORD: exactly 1000 '*' followed by a single '#'
> > 2.) LONGWORD: exactly 10000 '*' followed by a single '#'
> 
> Personally, I prefer:
> 
> STAR_WORD
> { int count = 0; }
>     :
>     ( '*' { count++; } )+ '#'
>     { if (count == 1000)
>           $setType(SHORTWORD);
>       else if (count == 10000)
>           $setType(LONGWORD);
>     }
> }
>     ;

It does not work. This grammar would accept 1001 (etc.) stars followed
by a single '#' as well.

Oliver


 

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