flatten-it.clj

(ns flatten-it)

(defn flatten-it [coll]
  (loop [acc [], aseq coll]
    (let [[fst & rst] aseq]
      (cond
        (empty? aseq) (seq acc)
        (sequential? fst) (recur (into acc (flatten-it fst)) rst)
        :otherwise (recur (into acc [fst]) rst)))))