Example code for Bisection method in Clojure

bisection.clj

; Example code for Bisection method
; https://en.wikipedia.org/wiki/Bisection_method

(defn f
  "Example function to apply algorithm on"
  [x]
  (+ 3 x))

(defn distance
  [a b]
  (Math/abs (float (- a b))))

(defn get-sign
  "Returns 1 or -1 depending if the number es positive or negative. If the
  number is 0 or NaN returns nil"
  [xraw]
  (let [x (float xraw)]
    (try
      (int (/ x (Math/abs x)))
      (catch Exception e
        nil))))

(defn good-half
  "Take the half of the segment where ends have different signs"
  [a b f]
  (let [c (/ (+ a b) 2)]
    (cond
      (= 0.0 c)
      [c c]
      (not= (get-sign (f c)) (get-sign (f a)))
      (sort [c a])
      (not= (get-sign (f c)) (get-sign (f b)))
      (sort [c b]))))

(defn bolzano
  "Apply Bolzano's algorithm to get the 0s of a function"
  [init-a init-b f max-err]
  (loop [[a b] [init-a init-b]]
    (println "New section: " a b)
    (if (< max-err (distance a b))
      (recur (good-half a b f))
      (/ (+ a b) 2))))