specialization.ml

module type s = sig
  type 'a t
  val hash : 'a t -> int
  val equal : 'a t -> 'a t -> bool
end


module Id: s = struct
  type 'a t = {
    id : int;
    contents : 'a;
  }

  let hash { id; _ } = id

  let equal a b = a.id = b.id

end

module Spec(T:sig type t end) =
struct
  type 'a aux = T.t Id.t
  type t = T.t aux
  include (Id:  s with type 'a t := 'a aux)
end


module H = Hashtbl.Make(Spec(struct type t = int end))