Jaro similarity in Clojure

jaro.clj

(defn ordered-matches
  [s1 s2]
  (let [enumerate   (fn [coll] (map-indexed vector coll))
        floor       (fn [x] (Math/floor x)) ; cljs: (.floor js/Math x)
        window-span (-> (max (count s1) (count s2))
                        (/ 2) floor dec)]
    (remove nil?
      (for [[i top] (enumerate s1)] ; cannot be put into a single for-comprehension
        (first
          (for [[j bottom] (enumerate s2)
                :when (and (= top bottom)
                           (<= (- i window-span) j (inc (+ i window-span))))]
             top))))))

(defn jaro-similarity
  "Returns the Jaro similarity of two strings (1 = exact match)."
  [s1 s2]
  (let [m1 (ordered-matches s1 s2)
        m2 (ordered-matches s2 s1)]
    (if (empty? m1) 0
      (let [m           (count m1)
            non-matches (->> (map = m1 m2) (filter false?) count)
            t           (/ non-matches 2)]
        (/ (+ (/ m (count s1)) (/ m (count s2)) (/ (- m t) m)) 3)))))