gistfile1.clj

(defn alternates
  "Split coll into 'threads' subsequences (defaults to 2), feeding
each alternately from the input sequence. Effectively the inverse of
interleave:

    (alternates 3 (range 9))
;=> ((0 3 6) (1 4 7) (2 5 8))"
  ([coll] (alternates 2 coll))
  ([threads coll]
   (for [offset (range threads)]
     (take-nth threads
               (drop offset coll)))))