1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
;; -*-theme-d-*-
;; Copyright (C) 2016, 2021 Tommi Höynälänmaa
;; Distributed under GNU Lesser General Public License version 3,
;; see file doc/LGPL-3.
(define-body (standard-library promise)
(define-param-method make-promise (%type)
(((proc (:procedure () %type pure)))
(:promise %type)
pure)
(let-volatile ((result-ready? <boolean> #f)
(result (:maybe %type) null))
(lambda (() %type pure)
(if result-ready?
(cast %type result)
(let ((x (proc)))
(if result-ready?
(cast %type result)
(begin (set! result-ready? #t)
(set! result x)
x)))))))
(define-param-method force (%type)
(((promise (:promise %type)))
%type
pure)
(promise))
(define-param-method make-nonpure-promise (%type)
(((proc (:procedure () %type nonpure)))
(:nonpure-promise %type)
pure)
(let-mutable ((result-ready? <boolean> #f)
(result (:maybe %type) null))
(lambda (() %type nonpure)
(if result-ready?
(cast %type result)
(let ((x (proc)))
(if result-ready?
(cast %type result)
(begin (set! result-ready? #t)
(set! result x)
x)))))))
(define-param-method force-nonpure (%type)
(((promise (:nonpure-promise %type)))
%type
nonpure)
(promise)))
|
