Implementation of the square root function, based on SICP Lecture 1A

square-root.clj

(ns example.square-root)

(def tolerance 0.00000000001)

(defn square [x]
  (* x x))

(defn avg [& args]
  (/ (apply + args)
     (count args)))

(defn abs [x]
  (if (>= x 0)
    x
    (- x)))

(defn improve-guess [g x]
  (avg g (/ x g)))

(defn close-enough? [g x]
  (< (abs (- x (square g)))
     tolerance))

(defn attempt [g x]
  (if (close-enough? g x)
    g
    (attempt (improve-guess g x) x)))

(defn square-root [x]
  (attempt 1 x))