(*

 * Global - Mutable global variable

 * Copyright (C) 2003 Nicolas Cannasse

 * 

 * 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 special exception on linking described in file 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

 *)

exception Global_not_initialized of string

type 'a t = ('a option ref * string)

let empty name = ref None,name

let name = snd

let set (r,_) v = r := Some v

let get (r,name) =

  match !r with

  | None -> raise (Global_not_initialized name)

  | Some v -> v

let undef (r,_) = r := None

let isdef (r,_) = !r <> None

let opt (r,_) = !r