[antlr-interest] Syntactic predicate in lexer rule

[Terence Parr]

On Jan 2, 2006, at 10:25 AM, Terence Parr wrote:

> On Jan 1, 2006, at 7:01 PM, Martin Traverso wrote:
>> FLOAT:  (DIGITS '.' DIGITS) => DIGITS '.' DIGITS;
>
> An alt with a single pred makes no sense, I'm afraid.  Predicates  
> indicate which of 2+ alts to match.

Actually, I take this back.  There is a quirk i just realized.  Syn  
preds are converted to sem preds (at least for now) for  
implementation, hence, they will be hoisted like any other  
predicate.  The (DIGITS '.' DIGITS) is converted to a boolean test  
and hoisted into the artificial Tokens rule and that might work.

I suggest looking at the DFA for Tokens rule to see how it  
looks...should be an option in antlrworks for that.

Ter