34 lines
756 B
Scheme
34 lines
756 B
Scheme
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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
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; Fluid variables
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(define (make-fluid val)
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(vector '<fluid> val))
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(define (fluid f) (vector-ref f 1))
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(define (set-fluid! f val)
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(vector-set! f 1 val))
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(define (let-fluid f val thunk)
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(let ((swap (lambda () (let ((temp (fluid f)))
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(set-fluid! f val)
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(set! val temp)))))
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(dynamic-wind swap thunk swap)))
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(define (let-fluids . args) ;Kind of gross
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(let loop ((args args)
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(swap (lambda () #f)))
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(if (null? (cdr args))
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(dynamic-wind swap (car args) swap)
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(loop (cddr args)
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(let ((f (car args))
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(val (cadr args)))
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(lambda ()
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(swap)
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(let ((temp (fluid f)))
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(set-fluid! f val)
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(set! val temp))))))))
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