(define (cuberoot_iter new_guess last_guess x)
	(if (good_enough? new_guess last_guess)
	  new_guess
	  (cuberoot_iter (improve new_guess x) new_guess x)
	)
)

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


(define (good_enough? guess last_guess) 
  (< (absolute (- guess last_guess)) 0.000000000000001))

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

(define (cbrt x) (cuberoot_iter (/ x 2.0) x x))

(print (cbrt 27))