(defn lazy-qs [[pvt & rst]]               ; deconstruct array, first element is pivot
  (when pvt                               ; if pivot is not nil
    (let [smaller #(< % pvt)]             ; define helper function
      (lazy-cat
        (lazy-qs (filter smaller rst))    ; re-run fn with all elements smaller than pivot
        [pivot]                           ; center of list is pivot
        (lazy-qs (remove smaller rst)))))); re-run fn with all elements bigger than pivot