[antlr-interest] Re: TreeParsing with various roots

[Bryan Ewbank]

Paul,

Another option is to have each node have "type" (the usual beastie) and
provide a "subtype" field as well that contains the actual operator.

I'm doing that for qualifiers - "const", "static", etc all report as
#[QUALIFIER,name], but have a subtype field that contain a bitfield telling
me which qualifer was seen.

It requires intermediate rules in the parser to morph the tokens, but it
seems worth it to me...

    qualifier:
        : CONST  { ## = #[QUALIFIER, CONST->getText()]; ## ->
setSubtype(QUAL_CONST); }
        | STATIC { .... }


-- Bryan Ewbank
----- Original Message ----- 
From: "lgcraymer" <lgc at mail1.jpl.nasa.gov>
To: <antlr-interest at yahoogroups.com>
Sent: Wednesday, November 03, 2004 17:42
Subject: [antlr-interest] Re: TreeParsing with various roots


>
>
> Paul--
>
> Unfortunately, the answer to your question is "not yet".  Alternatives
> for roots should be supported--I started to do that for 2.8, but did
> not finish--but 2.x currently does not support them.
>
> 3.0 will:  Ter, Monty, and I discussed this at last summer's cabal.
>
> --Loring
>
>
> --- In antlr-interest at yahoogroups.com, "Paul J. Lucas"
> <pauljlucas at m...> wrote:
> > Suppose I have in a parser:
> >
> > compExpr
> >     : re1rangeExpr
> >       (co:compOp! re:rangeExpr!
> >       {
> >     ## = #(co, re1, re2)
> > }
> >       )?
> >     ;
> >
> > compOp
> >     : EQ | NE | LT | LE | GT | GE
> >     ;
> >
> > How to I write the corresponding Treeparser?
> >
> > compExpr
> >     : #( xxx re1=rangeExpr re2=RangeExpr )
> >     ;
> >
> > What goes in the place of the "xxx"?  Ideally, I'd like to
> > share the code for all compOps.
> >
> > I *could* do:
> >
> > compOp
> >     : (EQ | NE | LT | LE | GT | GE)
> >     {
> >     ##.setType( COMP_OP );
> > }
> >     ;
> >
> > then:
> >
> > compExpr
> >     : #( co:COMP_OP re1=rangeExpr re2=RangeExpr )
> >     {
> >     // do something with co.getText()
> > }
> >     ;
> >
> > But having to use the text of the original token seems a bit
> > hokey to me.  Is there a better way?
> >
> > - Paul
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>



 
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