問題2-10

こんなかんじ？

(define (div-interval x y)
  (let ((l-div (/ 1.0 (upper-bound y)))
	(r-div (/ 1.0 (lower-bound y))))
    (if (and (<= l-div 0) (=> r-div 0))
	(error "invalid interval")
	(mul-interval x
		      (make-interval l-div r-div)))))

今日朝いそいでて確かめてない＞＜