(* Copyright (C) 2003-2006 Henry Cejtin, Matthew Fluet, Suresh
 *    Jagannathan, and Stephen Weeks.
 *
 * MLton is released under a BSD-style license.
 * See the file MLton-LICENSE for details.
 *)

structure MLtonWeak =
   struct
      structure Weak = Primitive.MLton.Weak

      type 'a t = 'a Weak.t

      val new = Weak.new

      fun get (w: 'a t): 'a option =
         let
            (* Need to do the canGet after the get.  If you did the canGet first,
             * there could be a GC that invalidates the pointer between the
             * canGet and the get.
             *)
            val x = Weak.get w
         in
            if Weak.canGet w
               then SOME x
            else NONE
         end
   end