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
|
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees
; Fluid variables
(define (make-fluid val)
(vector '<fluid> val))
(define (fluid f) (vector-ref f 1))
(define (set-fluid! f val)
(vector-set! f 1 val))
(define (let-fluid f val thunk)
(let ((swap (lambda () (let ((temp (fluid f)))
(set-fluid! f val)
(set! val temp)))))
(dynamic-wind swap thunk swap)))
(define (let-fluids . args) ;Kind of gross
(let loop ((args args)
(swap (lambda () #f)))
(if (null? (cdr args))
(dynamic-wind swap (car args) swap)
(loop (cddr args)
(let ((f (car args))
(val (cadr args)))
(lambda ()
(swap)
(let ((temp (fluid f)))
(set-fluid! f val)
(set! val temp))))))))
(define (fluid-cell-ref f)
(cell-ref (fluid f)))
(define (fluid-cell-set! f val)
(cell-set! (fluid f) val))
|
