is this the issue?
http://www.antlr.org:8888/browse/ANTLR-189
Ter
On Aug 13, 2008, at 8:57 AM, Ned Gill wrote:
> I think I've found a problem with ANTLR's lexer generation. Here's a
> small
> example that shows the problem:
>
> grammar Problem;
>
> EOL : '\n' ;
> BAB : 'BAB' ;
>
> SYMBOL : 'A'|'B' ;
>
> line
> : SYMBOL* EOL
> ;
>
> script
> :
> ( line
> {
> System.out.print($line.text);
> }
> )*
> ;
>
>
> My test input looks like this:
>
> AAA
> AAB
> ABB
> BAA
>
>
> Lines 1-3 parse fine, but the lexer barfs on line 4. Here's the
> output:
>
> line 4:2 mismatched character 'A' expecting 'B'
> AAA
> AAB
> ABB
>
>
> The prediction code in the lexer's mTokens method looks like this
> (with my
> comments):
>
> switch ( input.LA(1) ) {
> case '\n':
> {
> alt1=1; // EOL
> }
> break;
> case 'B':
> {
> int LA1_2 = input.LA(2);
>
> if ( (LA1_2=='A') ) {
> alt1=2; // BAB
> }
> else {
> alt1=3;} // SYMBOL
> }
> break;
> case 'A':
> {
> alt1=3; // SYMBOL
> }
> break;
> default:
> NoViableAltException nvae =
> new NoViableAltException("", 1, 0, input);
>
> throw nvae;
> }
>
>
> It looks like it's not looking far enough ahead to determine that what
> it's looking at is really a BAB. I've seen the same behaviour in 3.0
> and
> 3.1.
>
> Is this a problem with ANTLR or my expectations?
>
>
> Cheers,
> Ned.
>
> _______________________________________________
> antlr-dev mailing list
> [email protected]
> http://www.antlr.org:8080/mailman/listinfo/antlr-dev
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