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rld.clj

(defn rle
  ([coll]
   (rle [] coll))
  ([result coll]
   (if (empty? coll)
     coll
     (lazy-seq
      (let [current (first coll)
            n (count (take-while #(= % current) coll))]
        (cons [n current] (rle result (drop n coll))))))))


(defn rld
  ([coll] (rld [] coll))
  ([result coll]
   (if (empty? coll)
     coll
     (lazy-seq
      (let [[n x] (first coll)
            remainder (if (= 1 n)
                        (rest coll)
                        (cons [(dec n) x] (rest coll)))]
        (cons x (rld result remainder)))))))