59 lines
1.6 KiB
Scheme
59 lines
1.6 KiB
Scheme
; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees. See file COPYING.
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; Lost: (ARITHMETIC-SHIFT 5 27) => -402653184 [wanted 671088640.]
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; Lost: (ARITHMETIC-SHIFT 5 28) => 268435456 [wanted 1342177280.]
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(define (testit name proc x y z)
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(let ((result (proc x y)))
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(if (not (= result z))
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(begin (display "Lost: ")
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(write `(,name ,x ,y))
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(display " => ")
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(write result)
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(display " [wanted ")
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(write z)
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(display "]")
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(newline)))))
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(define most-positive-fixnum
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(let ((n (arithmetic-shift 2 27))) (+ n (- n 1))))
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(define (test-left-shifts x)
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(let ((crossover (arithmetic-shift 2 27)))
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(do ((y 0 (+ y 1))
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(z x (* z (if (>= z crossover) 2. 2))))
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((= y 34))
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(testit 'arithmetic-shift arithmetic-shift x y z))))
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(test-left-shifts 5)
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(test-left-shifts -5)
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(define (test-right-shifts x)
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(do ((y 0 (- y 1))
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(z x (quotient z 2)))
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((= y -34))
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(testit 'arithmetic-shift arithmetic-shift x y z)))
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(test-right-shifts (* 5 (expt 2 36)))
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(test-right-shifts (* -5 (expt 2 36)))
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(define (bit1? x)
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(if (< x 0)
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(even? (quotient (- -1 x) 2))
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(odd? (quotient x 2))))
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(define (try-truth-table name proc predicate)
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(do ((x -4 (+ x 1)))
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((= x 4))
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(do ((y -4 (+ y 1)))
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((= y 4))
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(testit name proc x y
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(+ (if (predicate (odd? x) (odd? y)) 1 0)
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(if (predicate (bit1? x) (bit1? y)) 2 0)
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(if (predicate (negative? x) (negative? y)) -4 0))))))
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(try-truth-table 'bitwise-and bitwise-and (lambda (a b) (and a b)))
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(try-truth-table 'bitwise-ior bitwise-ior (lambda (a b) (or a b)))
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