]> Thomas Gazagnaire wrote: > Or you can also functorize your own piece of code : > > module Make (A : sig type t end) = > struct > > module rec H : > sig > type 'a node = > | Node of 'a node J.t > | Leaf of 'a > > type t = A.t node > val equal : t -> t -> bool > val hash : t -> int > end = > struct > type 'a node = > | Node of 'a node J.t > | Leaf of 'a > > type t = A.t node > let equal = (==) > let hash = Hashtbl.hash > end > > and J : Hashtbl.S with type key = A.t H.node = Hashtbl.Make( H ) > > end > Incredible! You have just provided a excellent solution. Works "out of the box": # module N = Make(struct type t = int end ) ;; # let jls = J.create 13 ;; val jls : '_a N.J.t = <abstr> # let r = H.Node(jls) ;; val r : '_a N.H.node = N.H.Node <abstr> # let _ = J.add jls r r ;; - : unit = () # let x = J.find jls r ;; val x : int N.H.node = N.H.Node <abstr> # let r = (x == r ) ;; val r : bool = true Hmmm... now I wonder if that node type can also be pulled in by the functor. If so we have a very general solution to the problem of equality checking of polymorphic types. Anyone care to comment? Once again Thomas, thank you. Hugo F. > 2009/1/20 Hugo Ferreira <hmf@inescporto.pt <mailto:hmf@inescporto.pt>> > > David Teller wrote: > > It's probably feasible without copy & paste by building a > functor on top > of the defunctorized hashtable in Batteries. Or by just using the > defunctorized hashtable of Batteries directly, although it's not > as safe > as the functorized version, due to the absence of existential types. > > > If I understand you correctly I would have to redefine equivalents for: > - HashedType > - S > - Make(H: HashedType) > > Basically copy & paste these and change the type. > Doable although not to my liking. > > TIA, > Hugo F. > > > > Cheers, > David > > On Tue, 2009-01-20 at 12:24 +0100, Daniel Bünzli wrote: > > Le 20 janv. 09 à 11:59, Hugo Ferreira a écrit : > > Is it possible to make H comply with Hashtbl.HashedType > i.e: make > J.Key = 'a H.node ? > > This issue is well known (e.g. see here [1]). Your are > running into limitations of the standard library. The only > unsatisfying answer is to copy the code from the standard > library and add the parameter yourself. > > Best, > > Daniel > > [1] > http://groups.google.com/group/fa.caml/browse_thread/thread/f2acb593da91553c?hl=fr&ie=UTF-8&q=type+var+in+functor+fa.caml > <http://groups.google.com/group/fa.caml/browse_thread/thread/f2acb593da91553c?hl=fr&ie=UTF-8&q=type+var+in+functor+fa.caml> > > ____________________________________________ugs > > > _______________________________________________ > Caml-list mailing list. Subscription management: > http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list > Archives: http://caml.inria.fr > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > Bug reports: http://caml.inria.fr/bin/caml-bugs > >