[antlr-interest] tree transformation in Parser PLEASE

[Bryan Ewbank]

Speaking just for me, I simply had to delete a weeks worth of mailing
list stuff (vacation)...

You have this:
    #( = A #( = B #( = C 4 ) ) )
And you want to replace it with this:
    #( = C 4 ) #( = B 4 ) #( = A 4 )

The hard part, from an ANTLR point of view, is knowing that you must
duplicate the node containing the constant.

Generally, in a following TreeParser, you can do this as shown below. 
There may be errors (I didn't test this), but it should be close to
what you need.  Note that I'm using C++ in my actions; if you're using
Java, your actions will be different.

// wrap resulting list of EQUALS nodes with a single root node
parent_rule
: xform_rule { ## = #( #[ROOT,"ROOT"], ## ); }
;

// flatten cascading EQUALS into a sequence of EQUALS nodes
xform_rule
returns [ RefAST r ]
    : #( EQUALS id
             ( c:constant
                    // node at the bottom of the EQUALS cascade
                    { r = #c; }
             | r=x:xform_rule
                    {
                        // intermediate node; convert to flattened
node.  the constant value
                        // is copied in this operation to avoid
destroying the tree...
                        ## = #( #[EQUALS,"="], #id, COPY(r) );
                        ##->setNextSibling(#x);
                    }
             ) // end of alternative
       )  // end of #EQUALS
;