問題1.8

僕の解答

こんな感じかな…

(define (improve guess x)
	(/ (+ (/ x (* guess guess)) (* 2 guess)) 3))

(define (good-enough? x guess)
	(< (abs (- (* guess guess guess) x)) 0.001))

(define (cubic-iter guess x)
	(if (good-enough? x guess)
	    guess
	  (cubic-iter (improve guess x)
		     x)))

(define (cubic x)
	(cubic-iter 1.0 x))


(display (cubic 8))
(newline)

解答例

• http://oss.timedia.co.jp/show/SICP/ex-1.8
• http://www.csus4.net/hiki/SICPReading/?naoya_t+%28naochan%29#l84

所感

good-enough?は改良版を使ってるなぁ。