[antlr-interest] ANTLR & equals()/Equals() [Re: A way to find all subtrees of a particular type?]

[lgcraymer]

In other words, you wanted a context-dependent equality for ASTs.  
That strikes me as a really bad idea--AST nodes represent elements 
in context-free grammars and ANTLR manipulates these as context-free 
entities unless the programmer specifies the context dependency via 
semantic predicates.  The "text and type" approach is much more 
natural for the problem domain.

--Loring


--- In antlr-interest at yahoogroups.com, "micheal_jor" 
<open.zone at v...> wrote:
> > There is a quick fix.  Redefine "equals" in your base AST class 
so 
> > that some text string--say ""--matches anything.
> 
> <SNIP>
> 
> Sorry for hijacking this thread but this reminded of one of the 
items 
> on my ANTLR to-do list (no, seriously):
> 
> "Moan about ANTLR's use of equals() in Java/C++ (and Equals() in 
C#)."
> 
> We recently had a situation where we wished to consider Tokens/AST-
> Nodes equal only if they had the same type, text and came from the 
> same file. Simply re-defining equals/Equals for our Token/AST 
> subclass would have been the natural approach however, that broke 
> many other little bits since ANTLR generated code sometimes 
depends 
> on it's (re-)definition of equality.
> 
> Can we move ANTLR's notion of equality to some other method - 
perhaps 
> hasSameTypeAndText()/HasSameTypeAndText()- so that equals()/Equals
() 
> can once again assume their intended meanings please?
> 
> Cheers,
> 
> Micheal


 

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