25 lines
720 B
Scheme
25 lines
720 B
Scheme
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;;; The procedure make-guardian is coped en verbatim
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;;; from Dybvig et al. Guardians paper.
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(library (ikarus guardians)
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(export make-guardian)
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(import (except (ikarus) make-guardian))
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(define make-guardian
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(lambda ()
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(let ([tc
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(let ([x (cons #f #f)])
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(cons x x))])
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(case-lambda
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[()
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(and (not (eq? (car tc) (cdr tc)))
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(let ([x (car tc)])
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(let ([y (car x)])
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(set-car! tc (cdr x))
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(set-car! x #f)
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(set-cdr! x #f)
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y)))]
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[(obj)
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(foreign-call "ikrt_register_guardian_pair" (cons tc obj))
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(void)])))))
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