ikarus/scheme/ikarus.control.ss

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;;; Ikarus Scheme -- A compiler for R6RS Scheme.
;;; Copyright (C) 2006,2007,2008 Abdulaziz Ghuloum
;;;
;;; This program is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License version 3 as
;;; published by the Free Software Foundation.
;;;
;;; This program is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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(library (ikarus control)
(export call/cf call/cc call-with-current-continuation dynamic-wind exit)
(import
(ikarus system $stack)
(except (ikarus) call/cf call/cc call-with-current-continuation
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dynamic-wind exit list-tail))
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(define primitive-call/cf
(lambda (f)
(if ($fp-at-base)
(f ($current-frame))
($seal-frame-and-call f))))
(define call/cf
(lambda (f)
(if (procedure? f)
(primitive-call/cf f)
(die 'call/cf "not a procedure" f))))
(define primitive-call/cc
(lambda (f)
(primitive-call/cf
(lambda (frm)
(f ($frame->continuation frm))))))
(define winders '())
(define len
(lambda (ls n)
(if (null? ls)
n
(len (cdr ls) (fxadd1 n)))))
(define list-tail
(lambda (ls n)
(if (fxzero? n)
ls
(list-tail (cdr ls) (fxsub1 n)))))
(define drop-uncommon-heads
(lambda (x y)
(if (eq? x y)
x
(drop-uncommon-heads (cdr x) (cdr y)))))
(define common-tail
(lambda (x y)
(let ([lx (len x 0)] [ly (len y 0)])
(let ([x (if (fx> lx ly) (list-tail x (fx- lx ly)) x)]
[y (if (fx> ly lx) (list-tail y (fx- ly lx)) y)])
(if (eq? x y)
x
(drop-uncommon-heads (cdr x) (cdr y)))))))
(define unwind*
(lambda (ls tail)
(unless (eq? ls tail)
(set! winders (cdr ls))
((cdar ls))
(unwind* (cdr ls) tail))))
(define rewind*
(lambda (ls tail)
(unless (eq? ls tail)
(rewind* (cdr ls) tail)
((caar ls))
(set! winders ls))))
(define do-wind
(lambda (new)
(let ([tail (common-tail new winders)])
(unwind* winders tail)
(rewind* new tail))))
(define call/cc
(lambda (f)
(unless (procedure? f)
(die 'call/cc "not a procedure" f))
(primitive-call/cc
(lambda (k)
(let ([save winders])
(f (case-lambda
[(v) (unless (eq? save winders) (do-wind save)) (k v)]
[() (unless (eq? save winders) (do-wind save)) (k)]
[(v1 v2 . v*)
(unless (eq? save winders) (do-wind save))
(apply k v1 v2 v*)])))))))
(define call-with-current-continuation
(lambda (f)
(unless (procedure? f)
(die 'call-with-current-continuation
"not a procedure" f))
(call/cc f)))
(define dynamic-wind
(lambda (in body out)
(unless (procedure? in)
(die 'dynamic-wind "not a procedure" in))
(unless (procedure? body)
(die 'dynamic-wind "not a procedure" body))
(unless (procedure? out)
(die 'dynamic-wind "not a procedure" out))
(in)
(set! winders (cons (cons in out) winders))
(call-with-values
body
(case-lambda
[(v) (set! winders (cdr winders)) (out) v]
[() (set! winders (cdr winders)) (out) (values)]
[(v1 v2 . v*)
(set! winders (cdr winders))
(out)
(apply values v1 v2 v*)]))))
(define exit
(case-lambda
[() (exit 0)]
[(status) (foreign-call "ikrt_exit" status)]))
)