57 lines
2.2 KiB
Scheme
57 lines
2.2 KiB
Scheme
;;; scratch.scm - a scheme utility library
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;;;
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;;; Copyright (c) 2011-2012 Johan Ceuppens
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;;;
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;;; All rights reserved.
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;;;
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;;; Redistribution and use in source and binary forms, with or without
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;;; modification, are permitted provided that the following conditions
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;;; are met:
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;;; 1. Redistributions of source code must retain the above copyright
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;;; notice, this list of conditions and the following disclaimer.
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;;; 2. Redistributions in binary form must reproduce the above copyright
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;;; notice, this list of conditions and the following disclaimer in the
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;;; documentation and/or other materials provided with the distribution.
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;;; 3. The name of the authors may not be used to endorse or promote products
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;;; derived from this software without specific prior written permission.
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;;;
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;;; THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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;;; IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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;;; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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;;; IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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;;; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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;;; NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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;;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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;;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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;;; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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;; inner syntax
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;; test
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;; (list-generate-element a b c) generates an element with each call
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(define (list-generate-element lst)
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(define (get-char return)
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(for-each
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(lambda (element)
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(set! return (call-with-current-continutation
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(lambda (r)
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(set! get-char r)
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(return element)))))
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lst)
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(return 'end-generate))
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(define (gen)
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(call-with-current-continuation get-char))
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gen)
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;; outer syntax
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;; test
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;; (list-gen a b c) gives an element of '(a b c) each call
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(define-syntax list-gen
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(syntax-rules ()
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((_ a ...)
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(list-generate-element (make-list a ...)))))
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