[antlr-interest] a simple (not for me :)) grammar problem

[Mark Volkmann]

Here is my attempt to stop parsing after the lexer gets a
NoViableAltException. It doesn't stop. Can someone tell me why? Here's
the output I get when I process "3 .14.hello". Note that the space
between the 3 and the dot isn't allowed by the grammar.

matched!
line 1:1 no viable alternative at character ' '

grammar Sample;

@lexer::members {
  protected void mismatch(IntStream input, int ttype, BitSet follow)
  throws RecognitionException {
    throw new MismatchedTokenException(ttype, input);
  }

  public void recoverFromMismatchedSet(
    IntStream input, RecognitionException e, BitSet follow)
  throws RecognitionException {
    throw e;
  }
}

@parser::members {
  protected void mismatch(IntStream input, int ttype, BitSet follow)
  throws RecognitionException {
    throw new MismatchedTokenException(ttype, input);
  }

  public void recoverFromMismatchedSet(
    IntStream input, RecognitionException e, BitSet follow)
  throws RecognitionException {
    throw e;
  }
}

@lexer::rulecatch {
  catch (RecognitionException e) {
    throw e;
  }
}

@parser::rulecatch {
  catch (RecognitionException e) {
    throw e;
  }
}

start
  options { backtrack = true; }
  : (floatValue | integerValue) DOT IDENTIFIER
    { System.out.println("matched!"); }
  ;

floatValue: NUMBER DOT NUMBER;
integerValue: NUMBER;

DOT: '.';
IDENTIFIER: LETTER+;
NUMBER: DIGIT+;
fragment LETTER: 'a'..'z';
fragment DIGIT: '0'..'9';

NEWLINE: '\r'? '\n' { skip(); };

On Jan 7, 2008 4:15 PM, Mark Volkmann <r.mark.volkmann at gmail.com> wrote:
> On Jan 7, 2008 2:35 PM, Fırat Küçük <firatkucuk at gmail.com> wrote:
> > no,
> > this is what i did.
> >
> > this grammar parses "3     .    4    . hello".
>
> The solution I emailed out doesn't parse that because it doesn't skip
> whitespace. Well, I should be more clear. This is the output I get.
>
>      [java] line 1:1 no viable alternative at character ' '
>      [java] matched!
>      [java] line 1:2 no viable alternative at character ' '
>      [java] line 1:4 no viable alternative at character ' '
>      [java] line 1:5 no viable alternative at character ' '
>      [java] line 1:8 no viable alternative at character ' '
>      [java] line 1:9 no viable alternative at character ' '
>      [java] line 1:11 no viable alternative at character ' '
>      [java] line 1:12 no viable alternative at character ' '
>
> So you see I get the message "matched!", but I also get all the "no
> viable alternative" messages. What we need is a way to make the parser
> stop when it gets one of those. I think this is addressed in section
> 10.4. I'll try that and let you know what happens.
>
>
> > so as gavin said.
> >
> >
> > "It's not a solution if it doesn't work :)"
> >
> >
> >
> >  2008/1/7, Mark Volkmann <r.mark.volkmann at gmail.com>:
> >
> > > On Jan 7, 2008 6:24 AM, Gavin Lambert <antlr at mirality.co.nz> wrote:
> > > > At 21:20 7/01/2008, =?ISO-8859-9?Q?F=FDrat_K=FC=E7=FCk?= wrote:
> > > >  >
> > > >  >this is my simple solution:
> > > >
> > > > It's not a solution if it doesn't work :)
> > > >
> > > > Try doing what I suggested.  You really should handle the floats
> > > > in the lexer, since you don't have to worry about whitespace
> > > > weirdness that way.  And if you do it the way I said, it should
> > > > work.
> > >
> > > I think this is what you want or at least really close.
> > >
> > > grammar Sample;
> > >
> > > start
> > >   options { backtrack = true; }
> > >   : (floatValue | integerValue) DOT IDENTIFIER
> > >     { System.out.println("matched!"); }
> > >   ;
> > >
> > > floatValue: NUMBER DOT NUMBER;
> > > integerValue: NUMBER;
> > >
> > > DOT: '.';
> > > IDENTIFIER: LETTER+;
> > > NUMBER: DIGIT+;
> > > fragment LETTER: 'a'..'z';
> > > fragment DIGIT: '0'..'9';
> > >
> > > NEWLINE: '\r'? '\n' { skip(); };
> > >
> > > --
> > > R. Mark Volkmann
> > > Object Computing, Inc.
> > >
> >
> >
> >
> >
> > --
> > Öğr. Gör. Fırat Küçük
> > ADAMYO Distance Learning
> > SAKARYA University / TURKEY
>
>
>
> --
>
> R. Mark Volkmann
> Object Computing, Inc.
>



-- 
R. Mark Volkmann
Object Computing, Inc.