sandbox experiment for tonight's meetup

sandbox.clj

(defn make-seq [item]
  (if (coll? item)
    item
    (list item)))

(defn flatten-once [items]
  (apply concat (map make-seq items)))

(defn flatten-all [items]
  (let [res (flatten-once items)]
    (if (some coll? res)
      (flatten-all res)
      res)))

(flatten-all [1 2 [3] [2 [4]]])

(flatten [1 2 [3] [2 [4]]])

(defn my-flatten [x]
  (filter (complement sequential?)
          (rest (tree-seq sequential? seq x))))

(sequential? [])
(sequential? #{})

(flatten [1 2 {:a [1 2 [[3]]] :b 2}])