[antlr-interest] Problems with semantic predicates

[Jim Idle]

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Gavin Lambert
> Sent: Thursday, April 17, 2008 1:31 PM
> To: Haralambi Haralambiev; antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Problems with semantic predicates
> 
> At 04:02 18/04/2008, Haralambi Haralambiev wrote:
> >r2[boolean flag]
> >:{flag}? Token1 -> ^(NODE Token1)
> >|Token1
> >;
> [...]
> >In the example above - the method synpred2_fragment() contains a
> >statement if ( !(flag) ) but the variable flag cannot be resolved.
> 
> As Johannes has already said, the problem is that the predicate is
> getting hoisted.  However, I think there's another way to get it
> to work -- rewrite the rule so that it doesn't *need* to hoist the
> predicate:

Right idea mate, slightly wrong syntax ;-) :

r2[boolean flag]
	:  Token1
	
		 {$flag}? 	-> ^(NODE Token1)
     				-> Token1
	;


> 
> r2[boolean flag]
>    :  Token1
>       ( {$flag}? => -> ^(NODE Token1)
>       | -> Token1
>       )
>    ;
> 

Jim
 

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