[antlr-interest] Tree Operators vs. Tree Rewrite Rules

[Jim Idle]

On Sat, 2008-10-25 at 11:57 +0200, Simon wrote:

> Is it so obvious? Or is it simply not possible to achieve the same  
> thing using rewrite rules?


Have you tried a few things yourself? It won't explode if you do it
wrong :-)

Try things akin to:

e
: p -> $p
   (
     a='.' i=id
       ->^($a $e $i) // Or $a $i $e
   )*
;

Jim


> 
> On Oct 22, 2008, at 3:07 PM, cocoa at gmx.ch wrote:
> 
> > Hi
> >
> > I try to build an AST for the following sentences:
> >
> > a.b.c;
> >
> > or
> >
> > a.b.c.d.e;
> >
> > The grammar is shown below. The expected tree (for the first  
> > example) is
> >
> > ^('.' ^('.' 'a' 'b') 'c')
> >
> > It works as expected with tree operators:
> >
> > prog
> > 	:	expr ';'!
> > 	;
> > 	
> > expr
> > 	:	primary ('.'^ ID )*
> > 	;
> >
> > primary
> > 	:	ID
> > 	;
> >
> > However, I can't get the same tree using tree rewrite rules. Is it  
> > possible at all? If so, could somebody please show me how?
> >
> > Thanks
> > Simon
> >
> > PS: ultimately, I want to build an AST for a Java like language  
> > (method calls, field access, ...)
> > -- 
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> >
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