[antlr-interest] Help! Predicate failed messages

[Jim Idle]

On Wed, 2008-12-03 at 17:41 +0800, chain one wrote:
> procedure_id
>     : { isFirst }? id=IDENT { addId($id.getText(),PROCEDURE_IDENT); } 
>              |  nid=PROCEDURE_IDENT { $nid.setType(IDENT);} ->
> ^(PROCEDURE_ID[] PROCEDURE_IDENT)
>              ;
> In the first pass, isFirst  is true, and in the second pass, isFirst
> is set to be false. 
> When running the generated Java code, it seems every time
> the predicate fails, there will be an error message coming out like
> this:
> 
> 
> line 43:41 rule named_types failed predicate: { isFirst }?
> 
> 
> 
> Could it be ignored? or there is something wrong with my grammar file?
> 


You need to use a gated semantic predicate not a semantic predicate.

{ isFirst }?=>

You should also read through the getting started with ANTLR 3 links on
antlr.org as they will save you a lot of time.

Jim

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