40 lines
1.4 KiB
Scheme
40 lines
1.4 KiB
Scheme
;;; Ikarus Scheme -- A compiler for R6RS Scheme.
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;;; Copyright (C) 2006,2007,2008 Abdulaziz Ghuloum
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;;;
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License version 3 as
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;;; published by the Free Software Foundation.
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;;;
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;;; This program is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;; General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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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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