[antlr-interest] Re: Building trees with the correct associativity

[Paul J. Lucas]

On Thu, 2 Dec 2004, lgcraymer wrote:

> I miswrote the second case which should have been
> 
> addExpr
>     :
>     mulExpr  (addOp addExpr)?
>     ;
> 
> and you can do the rewrite within the ()?.

	That still doesn't work: the tree is still right-associative,
	i.e., 5 - 2 + 3 equals 0 instead of 6.

> Out of curiosity, why are you avoiding the more compact
> 
> addExpr
>     :
>     mulExpr (addOp^ mulExpr)*
>     ;
> 
> The binary trees avoid inserting the extra node.

	Because that's illegal syntax in ANTLR 2.7.x.  addOp is not a
	token.  But this is orthoganal to the problem at hand.

	- Paul



 
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