On Apr 26, 2007, at 11:47 AM, Bradley Lucier wrote:
Here's a fix for the bug. (Marc, can you change this in _num.scm?)
Here's a somewhat better fix (faster for some "obvious" cases, which I hope are correct ;-).
(define-prim (##exact-int.div x y)
(define (big-quotient x y) (let* ((x-negative? (##negative? x)) (abs-x (if x-negative? (##negate x) x)) (y-negative? (##negative? y)) (abs-y (if y-negative? (##negate y) y))) (if (##< abs-x abs-y) (##cons 0 x) ;; at least one of x and y is a bignum, so ;; here abs-x must be a bignum (let ((result (##bignum.div abs-x abs-y))) (if (##not (##eq? x-negative? y-negative?)) (##set-car! result (##negate (##car result)))) (if x-negative? (##set-cdr! result (##negate (##cdr result)))) result))))
(cond ((##eq? y 1) (##cons x 0)) ((##eq? y -1) (##cons (##negate x) 0)) ((##eq? x y) ;; can come up in rational arithmetic (##cons 1 0)) ((##fixnum? x) (if (##fixnum? y) (##cons (##fixnum.quotient x y) ; note: y can't be -1 (##fixnum.remainder x y)) ;; y is a bignum, x is a fixnum (if (##fixnum.< 1 (##bignum.adigit-length y)) ;; y has at least two adigits, so ;; (abs y) > (abs x) (##cons 0 x) (big-quotient x y)))) ((and (##bignum? y) (##fixnum.< 1 (##fixnum.- (##bignum.adigit-length y) (##bignum.adigit-length x)))) ;; x and y are bignums, and y has at least two more adigits ;; than x, so (abs y) > (abs x) (##cons 0 x)) (else (big-quotient x y))))