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7f918cf1 CE |
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 |