merge-sort.clj

(ns adaa)

(defn merger
  [a b c]
  (if (every? empty? [a b])
    c
    (cond
     (empty? a) (merger a (rest b) (conj c (first b)))
     (empty? b) (merger (rest a) b (conj c (first a)))
     :else (if (< (first a) (first b))
             (merger (rest a) b (conj c (first a)))
             (merger a (rest b) (conj c (first b)))))))

(defn merge-sort
  [coll]
  (let [n (count coll) m (/ n 2)]
    (if (<= n 1)
      coll
      (merger (merge-sort (take m coll)) (merge-sort (drop m coll)) []))))

My first pass at merge sort. Causes a stack overflow at around n = 4000 ... so not very good :( Looking at this gist now for inspiration.