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
|
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Mike Sperber
;; This replaces trans-id REF in Reppy's code
(define-synchronized-record-type trans-id :trans-id
(really-make-trans-id thread-cell value)
(value)
trans-id?
(thread-cell trans-id-thread-cell)
(value trans-id-value set-trans-id-value!))
(define (make-trans-id)
(really-make-trans-id (make-cell (current-thread))
#f))
(define (maybe-commit-and-trans-id-value trans-id)
(cond
((trans-id-value trans-id)
=> (lambda (value)
(and (maybe-commit)
value)))
(else
(and (maybe-commit-and-block (trans-id-thread-cell trans-id))
(trans-id-value trans-id)))))
(define (trans-id-set-value! trans-id value)
(cond
((not value)
(assertion-violation 'trans-id-set-value! "trans-id value can't be #f"
trans-id value))
((trans-id-value trans-id)
(assertion-violation 'trans-id-set-value! "trans-id is already assigned"
trans-id value))
(else
(set-trans-id-value! trans-id value)) ))
(define (trans-id-cancelled? trans-id)
(and (trans-id-value trans-id) #t))
|
