On 2/24/07, skaller <[EMAIL PROTECTED]> wrote:
> On Fri, 2007-02-23 at 15:24 +0100, Nicolas Pouillard wrote:
>
> > - Towards efficient, typed LR parsers:
> >    
> > http://cristal.inria.fr/~fpottier/publis/fpottier-regis-gianas-typed-lr.pdf
>
> Haskell 6.4 has GADTs already and Ocaml will have them soon?

<not official>
It was on plans but I think that Yann won't have enough time.
</ not official>

> Hmm .. ahh .. the key statement here says that tags of conventional
> constructors are stored physically in the variant object,
> but with a pushdown automaton the variant is already encoded
> in the automaton state variable, so the automaton state and
> stack cell variant tag are related. GADTs allow that relationship
> to be captured in a constraint which can be used to remove
> the redundant information.

Yep exactly, in some sense it's a way to get rid of this kind of code:

match f x with
| Some_case ... -> ...
| _ -> assert false (* it's not possible to go there *)

With GADT's you can eliminate the second case.

-- 
Nicolas Pouillard

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