Re: [Camllist] Polymorphic Variants and Number Parameterized Typ es
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Date:  20020502 (07:47) 
From:  Francois Pottier <francois.pottier@i...> 
Subject:  Re: [Camllist] Re: Encoding "abstract" signatures 
On Wed, May 01, 2002 at 03:19:29PM +0200, Andreas Rossberg wrote: > > This is just one reason. More generally, it's the need for a coherent > encoding in the higherorder setting we face. If we say that type > > functor(X : sig type t val x : t end) > ... > > maps to something like > > forall t. t > ... > > then consequently > > functor(Y : sig module type T end) > functor(X : Y.T) > ... > > must map to some type that yields the above as the result of some sequence > of applications. Oh, I see what you mean. It's a good point. But still I think I can encode the second functor as forall T. () > T > ... (where (), the empty structure type, corresponds to Y and T corresponds to X) which, when applied to an empty structure, yields forall T. T > ... as expected (provided the ``forall'' quantifier doesn't get in the way of application, i.e. polymorphic instantiation and abstraction are transparent, as in ML). > Well, besides the aforementioned problems, you don't represent type > abstraction at all (which, I would argue, is a central feature)  the > functor in question would not differ from > > functor F (X : sig module type T end) (Y : X.T) = Y Indeed it wouldn't. But I fail to see the point; if Y's type is X.T, there is no difference between Y and (Y : X.T), is there? The two functors in question have the same type in O'Caml.  François Pottier Francois.Pottier@inria.fr http://pauillac.inria.fr/~fpottier/  To unsubscribe, mail camllistrequest@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/camlbugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners