lib/mlton/basic/clearable-promise.sml

   1 (* Copyright (C) 1999-2006 Henry Cejtin, Matthew Fluet, Suresh
   2  *    Jagannathan, and Stephen Weeks.
   3  *
   4  * MLton is released under a BSD-style license.
   5  * See the file MLton-LICENSE for details.
   6  *)
   7
   8 structure ClearablePromise: CLEARABLE_PROMISE =
   9 struct
  10
  11 datatype 'a t = T of (unit -> 'a) * 'a Promise.t
  12
  13 fun clear (T (f, p)) = Promise.reset (p, f)
  14
  15 fun delay f = T (f, Promise.delay f)
  16
  17 exception Force = Promise.Force
  18
  19 fun force (T (_, p)) = Promise.force p
  20
  21 end