如何在clojure中求幂？ [英] How to do exponentiation in clojure?

问题描述

如何在clojure中进行取幂运算？
现在我只需要整数求幂，但问题也是分数。

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

推荐答案

经典递归（看这个，打击堆叠）

classic recursion (watch this, it blows stack)

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

尾递归

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

功能

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

< sneaky（也打击堆栈，但不是那么容易）

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)

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