Ex-1.45-todo

(define tolerance 0.00001)
(define (fixed-point f first-guess)
  (define (close-enough? v1 v2)
    (< (abs (- v1 v2)) tolerance))
  (define (try guess)
    (let ((next (f guess)))
      (if (close-enough? guess next)
          next
          (try next))))
  (try first-guess))
(define (average-damp f)
  (lambda (x) (average x (f x))))
(define (average x y)
  (/ (+ x y) 2))
(define (fast-expt b n)
  (cond ((= n 0) 1)
        ((even? n) (square (fast-expt b (/ n 2))))
        (else (* b (fast-expt b (- n 1))))))
(define (even? n)
  (= (remainder n 2) 0))
(define expt fast-expt)

;this needs to go only
(define (nth-root x n)
  (fixed-point (repeated
                (average-damp
                 (lambda (y) (/ x (expt y (- n 1)))))
                n) 1.0)) 

above isn't really working for (nth-root 3125 5)..