[antlr-interest] Re: "return" in rule code

[lgcraymer]

--- In antlr-interest at y..., "Paul J. Lucas" <dude at d...> wrote:
> Is it "OK" to have a "return" statement in a rule?
> 
> 	FOO
> 		: "foo" { if ( cond ) return; } "bar"
> 		;
> 
> Will the above match only "foo" if cond is true, i.e., abort the 
matching?
> 
> - Paul

Paul--

The right way to do this is with a semantic predicate:

FOO
         :
             "foo"  ( {cond}? "bar" | )
         ;

This is guaranteed to work; using "return" in an action could well 
bypass ANTLR tree construction (right now it doesn't, but it probably 
will in the next big--3.0--release when AST construction is 
optimized).

--Loring


 

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