[antlr-interest] unknown parameters

[Corno Schraverus]

> You cannot use parameters in predicates I am afraid, as when the
> predicate
> fragment is generated, the rule parameter is no longer in scope. I
> suspect
> that you are using the backtrack=true; option, which is where these
> options
> are coming from. If you wish to pass in such a parameter AND you wish
> to use
> backtrack=true, then you will need to use scopes rather than local
> parameters.
> 
> Overall it is probably best to get a grammar that does not use
> backtrack=true, but using scopes will solve your issue with parameters.
> 
> Jim
> 
That's correct, I'm using the 'backtrack=true' option, I'm working with the
Java 1.5 grammar that Terence made for Antlr3. If he wasn't able to create a
grammar without backtracking, I'm very much afraid that I won't be able to
improve on that.

I'm trying to understand if the fact that you can't combine parameters and
backtracking is an implementation issue or a conceptual issue. I could
imagine that the same fragment function is generated twice by antlr; one
with and one without parameters and actions. The first one is used during
probing and the second one is used when the right 'path' is found. Would
that be possible?

The actual issue I have is a bit more complicated than the example I showed,
I'm not passing the parameter directly, the parameter is a container and for
every matched subrule a component will have to be added to that container.
If I was to use scopes; would the following code be a 'good' solution?

bar [Bar * myBar]
	scope {
		Bar * bar_;
	}
	@init {
		$bar::bar_ = myBar;
	}
	:
	(
		{
			Foo * myFoo = new Foo();
			$bar::bar_.addFoo(myFoo);
		}
		foo [myFoo]
	 )*
	;

TIA,

Corno