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