(def tolerance 0.00001)
(defn fixed-point [f first-guess]
  (defn close-enough? [v1 v2]
    (< (math/abs (- v1 v2))
       tolerance))
  (defn try-it [guess]
    (let [next (* 0.5 (+ guess (f guess)))]
      (if (close-enough? guess next)
        next
        (try-it next))))
  (try-it first-guess))

(print (fixed-point (fn [x] (+ 1 (/ 1 x))) 1.0))