Ex_1_8(cube-root)

(define (square x) (* x x))

(define (cube x) (* x x x))

(define (abs x)
	(if (< x 0)
		(- x)
		x
	)
)

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

(define (good-enough? guess x)
	(< (abs (/ (- (cube guess) x) x))
		0.00001
	)
)

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

(define (cube-root x)
	(cube-root-iter 1.0 x)
)

(display (cube-root 8))