[antlr-interest] Advanced matching in Tree Parsers

[Bryan Ewbank]

Another option is to use syntactic predicates and recursion...

   // this is the entry point
   root:
      ( (pattern) => takeaction
      |
         // first instance of root is "down"; second is "to the right"
         #(. (root)? ) (root)?
      );
   pattern:
      #(A B)
   ;
   take_action:
      #(A #(B .... ) )
      { ## = kaboommmmmm; }
   ;

> What I really want to do is match patterns against the tree. The difference
> to how ANTLR is handling this is that I just want to check if the pattern
> fits, and if it fits execute some action (e.g. rewrite the tree). If the
> pattern is not matched I want to continue recursively through the tree
> (recursion, e.g. whole new expressions, can occur only in well defined
> places, don't have to match everything).