92 lines
2.4 KiB
Scheme
92 lines
2.4 KiB
Scheme
#| -*-Scheme-*-
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Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
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1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
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2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
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2017, 2018, 2019, 2020 Massachusetts Institute of Technology
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This file is part of MIT/GNU Scheme.
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MIT/GNU Scheme is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at
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your option) any later version.
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MIT/GNU Scheme 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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You should have received a copy of the GNU General Public License
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along with MIT/GNU Scheme; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
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USA.
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|#
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;;;; Rings
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(define (ring-list ring)
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(list-copy (vector-ref ring 2)))
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(define make-ring)
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(define ring-size)
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(define ring-clear!)
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(define ring-empty?)
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(define ring-push!)
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(define ring-pop!)
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(define ring-ref)
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(define ring-set!)
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(let ()
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(define (list-truncate! l i)
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(cond ((null? l) unspecific)
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((= i 1) (set-cdr! l '()))
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(else (list-truncate! (cdr l) (-1+ i))))
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unspecific)
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(set! make-ring
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(named-lambda (make-ring size)
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(if (< size 1)
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(error "Ring size too small" size)
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(vector "Ring" size '()))))
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(set! ring-size
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(named-lambda (ring-size ring)
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(length (vector-ref ring 2))))
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(set! ring-clear!
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(named-lambda (ring-clear! ring)
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(vector-set! ring 2 '())
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unspecific))
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(set! ring-empty?
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(named-lambda (ring-empty? ring)
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(null? (vector-ref ring 2))))
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(set! ring-push!
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(named-lambda (ring-push! ring object)
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(vector-set! ring 2 (cons object (vector-ref ring 2)))
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(list-truncate! (vector-ref ring 2) (vector-ref ring 1))))
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(set! ring-pop!
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(named-lambda (ring-pop! ring)
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(let ((l (vector-ref ring 2)))
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(if (null? l)
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(error "Ring empty" ring)
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(let ((object (car l)))
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(vector-set! ring 2 (append! (cdr l) (list object)))
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object)))))
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(set! ring-ref
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(named-lambda (ring-ref ring index)
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(list-ref (vector-ref ring 2) (modulo index (ring-size ring)))))
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(set! ring-set!
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(named-lambda (ring-set! ring index object)
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(list-set! (vector-ref ring 2) (modulo index (ring-size ring)) object)))
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)
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