[antlr-interest] Error in predicate logic

[Gerald B. Rosenberg]

At 12:57 AM 2/16/2007, Gavin Lambert wrote:
>At 06:42 16/02/2007, Gerald B. Rosenberg wrote:
>>SPCHAR
>>: ( AMP GRIDLET INT SEMI ) => AMP GRIDLET INT SEMI
>>| ( AMP LETTERS SEMI ) => AMP LETTERS SEMI
>>| ( AMP ) => AMP { $type=PCCHAR; }
>>;
>
>Ok, I could be wrong, but I don't think you need any of those 
>syntactic predicates, since your lookahead matches what you're 
>trying to parse anyway.

Right, but seems I still have to take care of the intervening states 
somehow to prevent getting the error message -- after a bit of trial 
and error, I found this to work:

SPCHAR :
     ( AMP GRIDLET INT SEMI    { printState("SpDigit "); }
     | AMP LETTERS SEMI        { printState("SpLettr "); }
     | AMP LETTERS ~';'        { $type=PCDATA; printState("P1Data  "); }
     | AMP GRIDLET INT ~';'    { $type=PCDATA; printState("P2Data  "); }
     | AMP GRIDLET ~INT        { $type=PCDATA; printState("P3Data  "); }
     | AMP                     { $type=PCDATA; printState("PcData  "); }
     ) ;

A bit literal.  Still, is there a better way?

Also, using ~SEMI  produced a lexer with an undefined set 
variable.  Using an explicit ~';' works, but seems counter-intuitive 
given that both the plain SEMI and  ~INT work.

>Oh, and what you call a GRIDLET is normally called a "hash 
>mark".  Except for some Americans, who inexplicably call it a "pound sign".

I have always taken "Gridlet" to be far more descriptive ;)

Thanks,
Gerald
----
Gerald B. Rosenberg, Esq.
NewTechLaw
285 Hamilton Avenue, Suite 520
Palo Alto, CA  94301-2576

650.325.2100  (office)  /  650.703.1724  (cell)
650.325.2107  (fax)

www.newtechlaw.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.antlr.org/pipermail/antlr-interest/attachments/20070216/65f1db64/attachment.html