(* 
 * ObservableFun - Observer Design Pattern, Functional Implementation v0.1
 * Copyright (C) 2007 Quôc Peyrot
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version,
 * with the following special exception.
 *
 * As a special exception to the GNU Library General Public License, you
 * may link, statically or dynamically, a "work that uses the Library"
 * with a publicly distributed version of the Library to produce an
 * executable file containing portions of the Library, and distribute
 * that executable file under terms of your choice, without any of the
 * additional requirements listed in clause 6 of the GNU Library General
 * Public License.  By "a publicly distributed version of the Library",
 * we mean either the unmodified Library as distributed, or a
 * modified version of the Library that is distributed under the
 * conditions defined in clause 3 of the GNU Library General Public
 * License.  This exception does not however invalidate any other reasons
 * why the executable file might be covered by the GNU Library General
 * Public License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *)

module Observable =
struct

  module ObserverMap = Map.Make (struct type t = string let compare = compare end)

  type 'a t = { value: 'a; observers: ('a -> unit) ObserverMap.t }

  let make value = { value = value; observers = ObserverMap.empty }

  let add_observer name callback a =
    { a with observers = ObserverMap.add name callback a.observers }

  let remove_observer name a =
    { a with observers = ObserverMap.remove name a.observers }

  let remove_all_observers a =
    { a with observers = ObserverMap.empty }

  let call_observers a =
    ObserverMap.iter (fun name callback -> callback a.value) a.observers

  let get a = a.value

  let set value a =
    let new_a = { a with value = value } in
    call_observers new_a;
    new_a

end

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