[antlr-interest] Previous rule element reference in a scope
Scott Stanchfield
scott at javadude.com
Wed Apr 13 05:52:49 PDT 2011
I'd suggest parameter passing here. Something like
withStatement
: 'With' id=ID
memberCallStatement[id]+
;
memberCallStatement[Token id]
: '.' ID '()' -> ^(CALL {$id} '.' ID)
;
-- Scott
----------------------------------------
Scott Stanchfield
http://javadude.com
On Wed, Apr 13, 2011 at 5:29 AM, Graham Mer <gd.antlr at gmail.com> wrote:
> Hello list,
>
> I have a grammar that includes a "With" statement like the following:
>
> With anObject
> .method1()
> .method2()
>
> which is semantically equivalent to the following fragment:
>
> anObject.method1()
> anObject.method2()
>
>
> During AST construction, I want to distribute 'anObject' to its
> subordinate method calls, so that I get a tree like the following:
>
> ^(CALL anObject.method1)
> ^(CALL anObject.method2)
>
> This is a natural fit for a scope, but I'm not sure how to capture the
> 'anObject' reference in a scope.
>
> If I have a recognizer grammar with the following rules, how do I
> capture the withStatement ID in a scope, and how do I insert that
> reference into the AST generated by memberCallStatement?
>
> withStatement
> scope{ // what do I store here to save my ID? }
> : 'With' ID
> ;
>
> memberCallStatement
> : '.' ID '()' // how do i insert $scope::ID in my AST?
> ;
>
> Also, are there any special precautions I need to take to avoid
> inserting loops in the AST, for example, do I need to make a new
> instance of the with object every time I duplicate it in the AST, or
> can I just re-use it? Is it best to use a String or my own Java
> object, or can I capture the thing that the recognizer generates
> directly?
>
> I wish I could do essentially the following:
>
> withStatement
> scope{ Object id; }
> : 'With'! id=ID!
> ;
>
> memberCallStatement
> : '.' ID '()' -> ^(CALL $withStatement::id '.' $ID)
> ;
>
> I know that will give ANTLR a sad, but I hope it illustrates what I
> want to produce.
>
>
> Thanks.
>
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