[antlr-interest] Rewrite separators to root nodes.

[Gavin Lambert]

At 21:44 4/08/2008, craig at palantir.co.za wrote:
 >rules:	rule (('and'|'or') rule)*
 >                ;
 >rule
 >:	ROOT xn+=xname (':' xn+=xname)+
 >	-> ^(ROOT xname*);
 >
 >I want to use tree rewrites to produce a tree that matches what 
i
 >have below.
 >
 >rule:    ^(ROOT 'and' xname*)
 >        |^(ROOT 'or' xname*)
 >        |^(ROOT xname*)

It might be possible to do that, but it'd be much easier to 
generate a slightly different structure.  If you change the 
'rules' rule to this:

rules:	rule (('and'|'or')^ rule)*;

It will produce trees that can be matched like this:

rules
   : ^('or' a=rules b=rules)
   | ^('and' a=rules b=rules)
   | rule
   ;
rule
   : ^(ROOT xname*)
   ;

I think that's much easier to deal with :)