[antlr-interest] question about example 'ANTLR masquerading as SED'

[Terence Parr]

On Sunday, December 22, 2002, at 03:42  PM, corno at dds.nl wrote:

> Hi all,
>
> The following example is from the reference manual.
>
> class T extends Lexer;
> options {
>   k=2;
>   filter=IGNORE;
>   charVocabulary = '\3'..'\177';
> }
>
> protected
> IGNORE
>   :  ( "\r\n" | '\r' | '\n' )
>      {newline(); System.out.println("");}
>   |  c:. {System.out.print(c);}
>   ;
>
>
> but it gives a warning about nondeterminism. However, when I comment 
> out the
> last code block (behind c:.), there's no warning, which seems strange 
> to me as
> it does not alter the logic (or does it).

It alters the logic because if you remove it takes out the alt that 
says "match anything (else)".  "anything" matches the newline stuff 
also so it's ambiguous.  You can shut off the warning if you want 
though with a subrule option.  Or, just ignore the warning ;)

Terence

> Can anybody tell me:
> a) Why this is
> b) If this can be ignored
> c) If not, how this can be solved
>
> TIA,
>
> Corno
>
>
>
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>
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