38 lines
807 B
Scheme
38 lines
807 B
Scheme
(library
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(utils)
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(export inc!
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dec!
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swap!
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fluid-let)
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(import (rnrs))
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(define-syntax inc!
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(syntax-rules ()
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((_ v) (set! v (+ 1 v)))
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((_ v n) (set! v (+ n v)))))
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(define-syntax dec!
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(syntax-rules ()
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((_ v) (set! v (- v 1)))
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((_ v n) (set! v (- v n)))))
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(define-syntax swap!
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(syntax-rules ()
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((_ x y)
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(let ((tmp x))
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(set! x y)
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(set! y tmp)))))
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(define-syntax fluid-let
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(syntax-rules ()
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((_ ((x e)) b1 b2 ...)
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(let ((y e))
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(let ((swap (lambda ()
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(let ((t x))
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(set! x y)
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(set! y t)))))
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(dynamic-wind swap (lambda ()
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b1 b2 ...)
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swap))))))
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)
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