[antlr-interest] Re: Syntactic predicate in lexer rule

[Xue Yong Zhi]

The lexer will definitely "try" to match FLOAT, if the token starts with 
DIGITS. But it will not accept it, since the syntactic predication will 
fail. That's expected behavior.

Martin Traverso wrote:
> Hi all,
> 
> Happy new year!
> 
> I'm having some trouble with the following grammar. I would think the 
> syntactic predicate in FLOAT should be enough to distinguish between a 
> FLOAT and an INTEGER followed by two dots, but when parsing stuff like 
> "1..2" the lexer tries to match a FLOAT. Any ideas why?
> 
> 
> grammar T;
> 
> range:  number ('..' number)?;
> number: INTEGER | FLOAT;
> 
> FLOAT:  (DIGITS '.' DIGITS) => DIGITS '.' DIGITS;
> 
> INTEGER : DIGITS;
> 
> fragment
> DIGITS: ('0'..'9')+;
> 
> 
> Thanks!
> 
> Martin