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

(define (improve guess x)
  (average guess (/ x guess))
  )

(define (average x y)
  (/ (+ x y) 2)
  )

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

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

(define (sqrt x)
  (sqrt-iter 1.0 x)
  )

(define (new-if predicate then-clause else-clause)
  (cond (predicate then-clause)
        (else else-clause)
        )
  )

(define (new-sqrt-iter guess x)
  "gre v neskoncni loop"
  (new-if (good-enough? guess x)
          guess
          (new-sqrt-iter (improve guess x)
                         x
                         )
          )
  )

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

(define (better-enough? g1 g2)
  "Sledimo spremembam priblizkov. Ustavimo, ko je sprememba majhen delez priblizka."
  (< (/ (- g1 g2) g1) 0.0001)
  )

(define (better-sqrt-iter guess x)
  "Better sqrt. Naloga 1.8."
  (let ((g2 (improve guess x)))
    (if (better-enough? g2 guess)
        g2
        (better-sqrt-iter g2 x)
        )
    )
  )

(define (improve-cube-root guess x)
  (/ (+ (* 2 guess) (/ x (* guess guess))) 3)
  )

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