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Ensuring exact-integer-sqrt always returns positive remainders.

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Moving out of (chibi) into only (scheme base).
This commit is contained in:
Alex Shinn 2013-01-05 23:45:30 +09:00
parent c559ae11be
commit 0daa2f270a
2 changed files with 10 additions and 7 deletions
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7
lib/init-7.scm
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@ -1039,13 +1039,6 @@
(define (eqv? a b) (if (eq? a b) #t (and (number? a) (equal? a b))))
(define (exact-integer-sqrt x)
(let ((res (sqrt x)))
(if (exact? res)
(values res 0)
(let ((res (inexact->exact (truncate res))))
(values res (- x (* res res)))))))
(define (zero? x) (= x 0))
(define (positive? x) (> x 0))
(define (negative? x) (< x 0))

10
lib/scheme/extras.scm
View file

@ -54,6 +54,16 @@
(define (floor/ n m)
(values (floor-quotient n m) (floor-remainder n m)))
(define (exact-integer-sqrt x)
(let ((res (sqrt x)))
(if (exact? res)
(values res 0)
(let lp ((res (inexact->exact (truncate res))))
(let ((rem (- x (* res res))))
(if (negative? rem)
(lp (- res 1))
(values res rem)))))))
;; Adapted from Bawden's algorithm.
(define (rationalize x e)
(define (sr x y return)