;;http://www.4clojure.com/problem/41
;;Write a function which drops every Nth item from a sequence.
;;(= (__ [1 2 3 4 5 6 7 8] 3) [1 2 4 5 7 8])
;;(= (__ [:a :b :c :d :e :f] 2) [:a :c :e])
;;(= (__ [1 2 3 4 5 6] 4) [1 2 3 5 6])
;;(= (__ [1 2 3 4 5 6 7 8] 3) [1 2 4 5 7 8])
(fn
  [base-seq remove-nth]
  (let [g (fn
            [base-seq remove-nth]
            (loop [x (- remove-nth 1)
                  result []]
              (if (< x (count base-seq))
                (recur (+ x remove-nth) (conj result x))
                result)))
        f (fn
            [base-seq remove-nth]
              (keep-indexed
                (fn
                  [index item]
                  (if (contains? (set remove-nth) index)
                    nil
                    item))
                base-seq))]
    (f base-seq (g base-seq remove-nth))))