[antlr-interest] ANTLR 2.7.7 TreeParser transformation question

[Kevin J. Cummings]

Never mind!  My bad!  I forgot to put (back?) the buildAST=true; option.
(I *hate* it when I do that!)  Things are working *much* better now.

Kevin J. Cummings wrote:
> Ric Klaren wrote:
>> Hi,
>>
>> On 4/14/07, Kevin J. Cummings <cummings at kjchome.homeip.net> wrote:
>>>> aexpr :! #( PLUS  p1:aexpr p2:aexpr )
>>>>          {
>>>>          // Anything plus 0 is Anything
>>>>            if (isZero(p1))
>>>>               {
>>>>                 #aexpr = #p2;
>>>>               }
>>>>            else if (isZero(p2))
>>>>               {
>>>>                 #aexpr = #p1;
>>>>               }
>>>>            else
>>>>               {
>>>>                 #aexpr = #(PLUS, p1, p2);
>>>>               }
>>>>          }
>>>>       |! ( #( MINUS aexpr aexpr ) )=> #( minus:MINUS m1:aexpr
>>> m2:aexpr )
>>>>       |! #( mult:MULT mu1:aexpr mu2:aexpr )
>>>>       |! #( div:DIV d1:aexpr d2:aexpr )
>>>>       |! #( neg:MINUS n:aexpr )
>>>>       | NUM
>>>>       | STRING
>>>>       ;
>>> What I'm trying to do is transform the tree passed into aexpr in those
>>> cases when I can remove complexity.  My isZero() method is correctly
>>> recognizing those NUM trees which contain the number "0".
>>> If I examine #aexpr before leaving this rule, I can see that:
>>>         (PLUS 2 0)
>>> is correctly reduced to just
>>>          2
>>>
>>> My problem is that the assignment to #aexpr appears in the .cpp code as
>>> a reference to:   aexpr_AST_in, but it is never used again after it gets
>>> assigned!
>>>
>>> The end of the case continues with assigning _retTree = _t and not my
>>> new tree.  The result of this is that when I examine my aexpr subtree in
>>> the bexpr rule, it is the original (PLUS 2 0) tree!  Not the transformed
>>> one!
>> Try using ## in stead of #aexpr. Does removing the ! from the first
>> alternative work as well?
> 
> Using ## generates:
> 
> 	aexpr_AST = RefGenevaAST(currentAST.root);
> 
> before the actions for the rule, but neither aexpr_AST nor currentAST
> are declared inside the code blocks in which they are used, and G++
> complains about this.
> 
> It doesn't seem to matter if I take the ! off the production rule or not.
> 
>> Cheers,
>>
>> Ric
>>
> 
> 

-- 
Kevin J. Cummings
kjchome at rcn.com
cummings at kjchome.homeip.net
cummings at kjc386.framingham.ma.us
Registered Linux User #1232 (http://counter.li.org)