[antlr-interest] Abstract syntax tree

[Bryan Ewbank]

To extend on normalizing the tree, I find it easier to avoid "(..)?"
operator when doing tree building; instead, I use an empty alternative
and build the tree explicitly.

// always a scope
interf: scope I_IDENT! IDENTIFIER^ ...

// but it might be empty, but the node is always in the tree
scope
    : (  /* NULL MATCH */
            { ## = #[NO_SCOPE]; }
      | PUBLIC
      | PRIVATE
      )
    ;

On Wed, 23 Feb 2005 06:38:44 -0800, John D. Mitchell
<johnm-antlr at non.net> wrote:
> One of the key tricks is reducing the complexity in each successive stage.
> 
> Don't make things in the AST optional.  I.e., in your parser, build an AST
> that has either a SCOPE node or a NO_SCOPE node.