Rational bozo sort

bozo.clj

(defn rational-bozo-sort
  "Choose, compare & if necessary exchange random indices n times, using the
   implicit ordering given by the lookup function"
  [lookup s n]
  (let [a (to-array s)
        c (alength a)]
    (dotimes [_ n]
      (let [idx1 (rand-int c)
            idx2 (rand-int idx1)
            v1 (aget a idx1)
            v2 (aget a idx2)]
        (when (< (lookup v1) (lookup v2))
          (aset a idx1 v2)
          (aset a idx2 v1))))
    (vec a)))