(**************************************************************************)
(* The OUnit library                                                      *)
(*                                                                        *)
(* Copyright (C) 2002-2008 Maas-Maarten Zeeman.                           *)
(* Copyright (C) 2010 OCamlCore SARL                                      *)
(* Copyright (C) 2013 Sylvain Le Gall                                     *)
(*                                                                        *)
(* The package OUnit is copyright by Maas-Maarten Zeeman, OCamlCore SARL  *)
(* and Sylvain Le Gall.                                                   *)
(*                                                                        *)
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(* a copy of this document and the OUnit software ("the Software"), to    *)
(* deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute,           *)
(* sublicense, and/or sell copies of the Software, and to permit persons  *)
(* to whom the Software is furnished to do so, subject to the following   *)
(* conditions:                                                            *)
(*                                                                        *)
(* The above copyright notice and this permission notice shall be         *)
(* included in all copies or substantial portions of the Software.        *)
(*                                                                        *)
(* The Software is provided ``as is'', without warranty of any kind,      *)
(* express or implied, including but not limited to the warranties of     *)
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(* In no event shall Maas-Maarten Zeeman be liable for any claim, damages *)
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(*                                                                        *)
(* See LICENSE.txt for details.                                           *)
(**************************************************************************)

(** Property list.

   @see <http://mlton.org/PropertyList> MLton property list.
  *)

type t = (int, unit -> unit) Hashtbl.t

let create () = Hashtbl.create 13

let new_property default =
  let id = Oo.id (object end) in
  let v = ref default in
  let set t x =
    Hashtbl.replace t id (fun () -> v := x)
  in
  let get t =
    try
      let x =
        (Hashtbl.find t id) ();
        !v
      in
        v := default;
        x
    with Not_found ->
      default
  in
    (set, get)
