120 lines
3.7 KiB
Scheme
120 lines
3.7 KiB
Scheme
;;;
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;;; Copyright (c) 1985 Massachusetts Institute of Technology
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;;;
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;;; This material was developed by the Scheme project at the
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;;; Massachusetts Institute of Technology, Department of
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;;; Electrical Engineering and Computer Science. Permission to
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;;; copy this software, to redistribute it, and to use it for any
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;;; purpose is granted, subject to the following restrictions and
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;;; understandings.
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;;;
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;;; 1. Any copy made of this software must include this copyright
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;;; notice in full.
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;;;
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;;; 2. Users of this software agree to make their best efforts (a)
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;;; to return to the MIT Scheme project any improvements or
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;;; extensions that they make, so that these may be included in
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;;; future releases; and (b) to inform MIT of noteworthy uses of
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;;; this software.
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;;;
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;;; 3. All materials developed as a consequence of the use of
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;;; this software shall duly acknowledge such use, in accordance
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;;; with the usual standards of acknowledging credit in academic
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;;; research.
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;;;
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;;; 4. MIT has made no warrantee or representation that the
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;;; operation of this software will be error-free, and MIT is
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;;; under no obligation to provide any services, by way of
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;;; maintenance, update, or otherwise.
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;;;
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;;; 5. In conjunction with products arising from the use of this
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;;; material, there shall be no use of the name of the
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;;; Massachusetts Institute of Technology nor of any adaptation
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;;; thereof in any advertising, promotional, or sales literature
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;;; without prior written consent from MIT in each case.
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;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;
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;;; Modified by Texas Instruments Inc 8/15/85
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;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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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-stack-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-ref l i)
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(cond ((null? l) (error "Index too large" 'LIST-REF))
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((zero? i) (car l))
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(else (list-ref (cdr l) (-1+ i)))))
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(define (list-set! l i o)
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(define (loop l i)
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(cond ((null? l) (error "Index too large" 'LIST-SET!))
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((zero? i) (set-car! l o))
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(else (list-ref (cdr l) (-1+ i)))))
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(loop l i))
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(define (list-truncate! l i)
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(cond ((null? l) 'DONE)
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((= i 1) (set-cdr! l '()))
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(else (list-truncate! (cdr l) (-1+ i)))))
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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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(let ((vec (make-vector 3)))
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(vector-set! vec 0 "Ring")
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(vector-set! vec 1 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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(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-stack-pop!
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(named-lambda (ring-stack-pop! ring n)
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(let ((l (vector-ref ring 2)))
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(if (> n (length l))
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(error "Ring does not have enteries" ring)
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(vector-set! ring 2 (list-tail l n))))))
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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) index)))
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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) index object)))
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)
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