take-nth.clj

(defnav take-nth [n]
  (select* [this structure next-fn]
    (next-fn (take-nth n structure)))
  (transform* [this structure next-fn]
    (if (vector? structure)
      (let [c  (count structure)
            is (into []
                 (take-while #(< % c))
                 (iterate #(+ % n) 0))]
        (reduce #(update %1 %2 next-fn) structure is))
      (sequence
        (map-indexed
          (fn [i x]
            (if (zero? (mod i n))
              (next-fn x)
              x)))
        structure))))

;; (sp/select (take-nth 2) [1 2 3 4 5])
ArityException Wrong number of args (2) passed to: misc/fn--28811  clojure.lang.AFn.throwArity (AFn.java:429)