xform.clj

(let [xparir-transform (fn [{:keys [initial-value transform-fn]}]
                         (fn [rf]
                           (let [old (volatile! initial-value)]
                             (fn
                               ([] (rf))
                               ([result] (rf result))
                               ([result input]
                                (let [new (transform-fn input @old)]
                                  (vreset! old input)
                                  (rf result new)))))))]
  (sequence (xparir-transform {:initial-value []
                               :transform-fn  (fn [current prev]
                                                (let [eq? (= (last current)
                                                             (last prev))]
                                                  (conj current (not eq?))))})
            [[1] [2] [2] [2] [3] [4]]))