いおりのプログラミングめも

(define (good-enough? guess next-guess) ;;許容値未満しか変化しなければ真
  (let ((tolerance 0.0001))
    (< (abs (- next-guess guess)) tolerance)))

;;;Newton法 p.14
(define (curt x) ;;立方根を求める
  (curt-iter 1.0 x))

(define (curt-iter guess x)
  (let ((next-guess (curt-improve guess x)))
    (if (good-enough? guess next-guess)
        next-guess
        (curt-iter next-guess x))))

(define (curt-improve y x)
  (/ (+ (/ x (square y))
        (* 2 y))
     3))