rand.clj

(ns foo.randomizer
  (:use [clojure.test]))

(defn delete [coll idx]
  (if (<= (inc idx) (count coll))
    (let [coll (vec coll)]
      (concat (subvec coll 0 idx) (subvec coll (inc idx) (count coll))))
    coll))

(defn randomize [coll]
  (loop [from coll to []]
    (if (seq from)
      (let [idx (rand-int (count from))]
        (recur (delete from idx) (conj to (nth (vec from) idx))))
      to)))

(deftest test-rand
  (testing "should return the same number of elements"
    (is (= 3 (count (randomize [1 2 3])))))
  (testing "should not be the same vector"
    (let [v (range 100)
          vprime (randomize v)]
      (is (not= v vprime))
      (is (apply = (map #(into #{} %) [v vprime]))))))

(comment
  (randomize ['tim 'phil 'kevin 'jim 'drew 'dan 'steve 'paul])

)