Merge sort in Clojure (probably not optimal)

merge_sort.clj

;; Quicky Merge sort and test

(defn merge-sort [coll]
  (letfn [(sort [coll]
            (if (= 1 (count coll)) coll
                (let [sz (count coll)
                      left (take (/ sz 2) coll)
                      right (drop (/ sz 2) coll)]
                  (merge (sort left) (sort right)))))
          (merge [left right]
            (loop [acc []
                   l left
                   r right]
              (cond (and (seq l) (not (seq r))) (recur (conj acc (first l)) (rest l) r)
                    (and (seq r) (not (seq l))) (recur (conj acc (first r)) l (rest r))
                    (and (seq l) (seq r)) (if (> (compare (first l) (first r)) 0)
                                            (recur (conj acc (first r)) l (rest r))
                                            (recur (conj acc (first l)) (rest l) r))
                    :else acc)))]
    (sort coll)))
;; => #'user/merge-sort

(require '(cemerick (pomegranate :refer :all)))
;; => nil

(add-classpath "/Users/Roberto/Code/yggdrasil/algorithms_1/lib/stdlib.jar")
;; => nil

(import In)
;; => In

;; Sorted
(let [sorted-coll (->> (In. "/Users/Roberto/Code/yggdrasil/algorithms_1/resources/8Kints.txt")
                       (.readAllInts)
                       (merge-sort))]
  (apply < sorted-coll))
;; => true

;; Works with duplicates
(let [ints (->> (In. "/Users/Roberto/Code/yggdrasil/algorithms_1/resources/8Kints.txt")
                      (.readAllInts))
            doubled (concat ints ints)
            sorted-coll (merge-sort doubled)]
        (apply <= sorted-coll))
;; => true