clj

; P09
(defn encode
  [coll]
  (if(empty? coll)
    coll
    (loop
      [left coll
       result []]
      (if(empty? left)
        result
        (let [[head & tail] left
             taken (take-while #(= head %) left)]
          (recur (drop-while #(= head %) tail) (conj result (list (count taken) head))))))))