INCLUDE "utils.ml"
module type S = 
sig
  type data
  type t
  val make : data -> t
  val node : t -> data
  val hash : t -> int
  val uid : t -> int
  val equal : t -> t -> bool
end
module Make (H : Hashtbl.HashedType) : S with type data = H.t =
struct
  type data = H.t
  type t =  { id : int;
	      key : int; (* hash *)
	      node : data;
	    }
  
  let node t = t.node
  let hash t = t.key
  let uid t = t.id
  let gen_uid  =
    let id = ref ~-1 in 
      fun () -> incr id;!id
  let equal t1 t2 = t1 == t2 || t1.id == t2.id
  module WH = Weak.Make( struct 
			   type _t = t 
			   type t = _t 
			   let hash = hash
			   let equal a b = H.equal a.node b.node 
			 end)
  let pool = WH.create MED_H_SIZE
  let make x = 
    let cell = { id = gen_uid(); key = H.hash x; node = x } in
      WH.merge pool cell
end