Re: [Caml-list] possible to define a type where = is forbidden ?

[Thomas Fischbacher <Thomas.Fischbacher@Physik.Uni-Muenchen.DE>]

On Mon, 10 Oct 2005, yoann padioleau wrote:

> > http://caml.inria.fr/pub/ml-archives/caml-list/2003/09/ 
> > f81c8063ed4878e06f1ddd8010256050.en.html
> 
> Interesting technique :)  but I think that it would not solve my problem. 
> 
> To be more precise my program analysis tool  try to compute "diff" between differents AST.
> So we love to use pattern-patching and to (ab)use the polymorphic  =  to compare stuff.
> 
> I don't see how your ExprAt technique will make this easier (not to mention that it also makes 
> the pattern matching ugly because I would have to wrap every  expression  with his ExprAt  because I want
> that the resultting  Ast_diff  contain also line number.

When you want to associate extra data to stuff that should retain nice 
comparison properties, another technique which might be useful or not is 
to use a weak pointer hash, mapping subtrees to positions.

I would not go so far as to say that this is the favored approach one 
should use, but sometimes this idea may be useful. At least, it's nice to 
have that trick available.

-- 
regards,               tf@cip.physik.uni-muenchen.de              (o_
 Thomas Fischbacher -  http://www.cip.physik.uni-muenchen.de/~tf  //\
(lambda (n) ((lambda (p q r) (p p q r)) (lambda (g x y)           V_/_
(if (= x 0) y (g g (- x 1) (* x y)))) n 1))                  (Debian GNU)