Multiway merge of sorted sequences

merge-sorted.clj

(defn merge-sorted [comparator & xss]
  (let [xss (into-array Object (remove empty? xss))
        pq  (java.util.PriorityQueue.
             (count xss) #(comparator (val %1) (val %2)))]
    (dotimes [i (count xss)]
      (let [xs (aget xss i)]
        (.add pq (pair i (first xs)))
        (aset xss i (next xs))))
    ((fn go []
       (lazy-seq
         (if-let [[i x] (.poll pq)]
           (let [ys (aget xss i)]
             (if-let [y (first ys)]
               (do (aset xss i (next ys))
                   (.add pq (pair i y))))
             (cons x (go)))))))))