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; "withfile.scm", with-input-from-file and with-output-to-file for Scheme
; Copyright (c) 1992, 1993 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1. Any copy made of this software must include this copyright notice
;in full.
;
;2. I have made no warrantee or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3. In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.
(require 'dynamic-wind)
(define withfile:current-input (current-input-port))
(define withfile:current-output (current-output-port))
(define (current-input-port) withfile:current-input)
(define (current-output-port) withfile:current-output)
(define (with-input-from-file file thunk)
(define oport withfile:current-input)
(define port (open-input-file file))
(dynamic-wind (lambda () (set! oport withfile:current-input)
(set! withfile:current-input port))
(lambda() (let ((ans (thunk))) (close-input-port port) ans))
(lambda() (set! withfile:current-input oport))))
(define (with-output-from-file file thunk)
(define oport withfile:current-output)
(define port (open-output-file file))
(dynamic-wind (lambda() (set! oport withfile:current-output)
(set! withfile:current-output port))
(lambda() (let ((ans (thunk))) (close-output-port port) ans))
(lambda() (set! withfile:current-output oport))))
(define peek-char
(let ((peek-char peek-char))
(lambda opt
(peek-char (if (null? opt) withfile:current-input (car opt))))))
(define read-char
(let ((read-char read-char))
(lambda opt
(read-char (if (null? opt) withfile:current-input (car opt))))))
(define read
(let ((read read))
(lambda opt
(read (if (null? opt) withfile:current-input (car opt))))))
(define write-char
(let ((write-char write-char))
(lambda (obj . opt)
(write-char obj (if (null? opt) withfile:current-output (car opt))))))
(define write
(let ((write write))
(lambda (obj . opt)
(write obj (if (null? opt) withfile:current-output (car opt))))))
(define display
(let ((display display))
(lambda (obj . opt)
(display obj (if (null? opt) withfile:current-output (car opt))))))
(define newline
(let ((newline newline))
(lambda opt
(newline (if (null? opt) withfile:current-output (car opt))))))
(define force-output
(let ((force-output force-output))
(lambda opt
(force-output (if (null? opt) withfile:current-output (car opt))))))
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