clojureexponentiation

How to do exponentiation in clojure?

How can I do exponentiation in clojure? For now I'm only needing integer exponentiation, but the question goes for fractions too.

Solution

  • classic recursion (watch this, it blows stack)

    (defn exp [x n]
     (if (zero? n) 1
         (* x (exp x (dec n)))))

    tail recursion 

    (defn exp [x n]
  (loop [acc 1 n n]
    (if (zero? n) acc
        (recur (* x acc) (dec n)))))

    functional

    (defn exp [x n]
  (reduce * (repeat n x)))

    sneaky (also blows stack, but not so easily)

    (defn exp-s [x n]
  (let [square (fn[x] (* x x))]
    (cond (zero? n) 1
          (even? n) (square (exp-s x (/ n 2)))
          :else (* x (exp-s x (dec n))))))

    library

    (require 'clojure.contrib.math)