gistfile1.txt

(defn
  #^{:doc "P11 (*) Modified run-length encoding."
     :test (do (test= (encode-modified '(a a a a b c c a a d e e e e))
                       '((4 a) b (2 c) (2 a) d (4 e)))
               (test= (encode-modified []) [])
               (test= (encode-modified [1]) [1]))}
; ---------------
  encode-modified
; ---------------
  ([coll]
     (if (empty? coll)
       []
       (map #(if (single? %)
               (first %)
               (list (count %) (first %)))
            (pack coll)))))

(defn single? [coll]
  (nil? (rest coll)))