[antlr-interest] validating semantic predicates

[Harald Mueller]

Hi -

You are already in a tree-parser, aren't you?
So some syntax parser has produced your trees (I don't assume you create the trees manually in some other way).
That syntax parser can then - in its tree-building rules (-> ...) - create trees which actually DO have terminating tokens - there is some documentation on such artificial tokens in the Wiki and also - I think - in the ANTLR book.
Hope this helps ...
Regards
Harald

-------- Original-Nachricht --------
> Datum: Fri, 30 Nov 2007 09:37:19 -0600
> Von: "Mark Volkmann" <r.mark.volkmann at gmail.com>
> An: antlr-interest at antlr.org
> Betreff: [antlr-interest] validating semantic predicates

> I'm trying to determine how to use validating semantic predicates in a
> rule that has no terminating token. Here's an example of the approach
> I've tried.
> 
> statement
>   : simpleStatement
>   | ^('if' c=condition { $c.result }? simpleStatement)
>   ;
>   catch[FailedPredicateException fpe] {
>     consumeUntil(input, STMT_TERMINATOR);
>     input.consume();
>   }
> 
> The problem is that simpleStatements have no terminating token. They
> are a keyword optionally foIlowed by a number. I know whether to
> expect the number based on the keyword. There's no such thing as
> STMT_TERMINATOR in my grammar.
> 
> I think in order to continue parsing when the condition evaluates to
> false, I have to consume all the tokens that make up the
> simpleStatement being skipped. How can I consume those tokens?
> 
> -- 
> R. Mark Volkmann
> Object Computing, Inc.

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