gistfile1.txt

module rec Value : sig
  type t =
    | Int of int
    | Tbl of t ValueTbl.t
  val hash : t -> int
  val equal : t -> t -> bool
end = struct
  type t =
    | Int of int
    | Tbl of t ValueTbl.t

  let hash = Hashtbl.hash

  let equal a b =
    match a, b with
    | Int x, Int y -> x = y
    | Tbl x, Tbl y -> x == y
    | _ -> false
end
and ValueTbl : Hashtbl.S with type key = Value.t = Hashtbl.Make (Value)