a-d-d with simple reduced checks

add.clj

(defn a-d-d [delay-size]
  (fn [rf]
    (let [state (volatile! [])]
      (fn
        ([] (rf))
        ([result]
         (let [buffer @state]
           (-> (if (seq buffer)
                 (rf result buffer)
                 result)
               (rf))))
        ([result input]
         (if (reduced? input)
           input
           (let [buffer (conj @state input)]
            (if (< (count buffer) delay-size)
              (do (vreset! state buffer)
                  result)
              (do (vreset! state [])
                  (rf result buffer))))))))))

;; under what scenarios ^^ fails?

(slow-into [] (comp (take 7)
                    (a-d-d-2 3)
                    (take 3))
           (range 10))

;; this returns  #object [clojure.lang.Reduced 1389120027 {:status :ready, :val #object [clojure.lang.Reduced 536311285 {:status :ready, :val [[0 1 2] [3 4 5] [6]]}]}] for both versions