SICP 問題1.8
ニュートン法で立方根を求める
(define (cube-root-iter guess x) (if (good-enough? guess x) guess (cube-root-iter (cube-improve guess x) x))) (define (cube-improve guess x) (/ (+ (/ x (square guess)) (* 2 guess)) 3)) (define (good-enough? guess x) (< (abs (- 1.0 (/ guess (cube-improve guess x)))) 0.001)) (define (cube-root x) (cube-root-iter 1.0 x))