[antlr-interest] How to access member of CommonTree subclass

Kaleb Pederson kaleb.pederson at gmail.com
Mon Oct 26 16:34:51 PDT 2009


On Monday 26 October 2009 04:18:21 pm Jim Idle wrote:
...
> > I'm working with a tree parser that is creating ASTs of a custom type.
> > This CommonTree subclass contains a member named elementType that
> > identifies the type represented by the tree.  How do I set the
> > elementType dynamically within an action?
> > 
> > I tried in the following way:
> > 
> > id:
> >   ^(AST_ID tok+=ID+)
> >   {
> >     $tree.setElementType( typeResolver.resolve(StringUtils.join($tok,
> > ".")) );
> >   }
> >   ;
> > 
> > This, however, doesn't work since the tree has not yet been set:
> 
> I presume that this is a tree walker that is producing another AST as output?

Correct.

> Anyway, why not return the value of typeResolver from the id rule, then set the resulting tree value?

That thought crossed my mind, but it seemed like it should be unnecessary. I gather then that it's not possible to set it directly?

>id : resolveID { $resovleID.tree.setElementType($resolveID.type); } ;
>
>resolveId
>returns [ xxx type]
>
>: ^AST_ID tok+=ID+) { $type =
>: typeResolver.resolve(StringUtils.join($tok,".")) );
>}
>;

Thanks for the suggestions.

--
Kaleb Pederson

Twitter - http://twitter.com/kalebpederson
Blog - http://kalebpederson.com


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