Kah0ona · September 7, 2017 19:39
diff --git a/test.clj b/test.clj
 (declare merge-peak-with-first)

 (defn concatenate-similar-peaks-xf []
  (fn [xf]
    (let [prev (volatile! ::none)]
      (fn
        ([] (xf))
        ([result] (xf result))
        ([result input]
         (let [prior @prev]
           (vreset! prev input)
           (if (= (:type prior) (:type input))
             ;;same type, merge the two peak-maps prior and input,
             ;;else, keep processing
             (-> result
                 pop ;; <-- !!! pop and conj are too specific functions that deal on collections. 
                     ;; What should I do to make this work?
                 (conj (merge-peak-with-first prior input)))
             (xf result input))))))))

 (defn merge-peak-with-first
  "Merges two peaks, the result will retain the values of p1 but:
   - :end_time will be become the value of p2
   - :peak will be the concat' value of p1 and p2"
  [p1 p2]
  (-> p1
      (update :peak
              (fn [p1-peak new-peak]
                (vec (concat p1-peak new-peak)))
              (:peak p2))
      (update :end-time
              (fn [_ new-end-time] new-end-time)
              (:end-time p2))))

 ;; Usage below
 ;; ===========
 (def test-peaks
    [{:type :a
      :peak [1 2]
      :end_time 1}
     {:type :a
      :peak [3 4]
      :end_time 2}
     {:type :a
      :peak [5 6]
      :end_time 3}
     {:type :b
      :peak []
      :end_time 8])

 ;; I want the result to be:
 ;; [{:type :a :peak [1 2 3 4 5 6] :end_time 3} 
 ;;  {:type :b :peak [] :end_time 8}]      
 (into [] (concatenate-similar-peaks-xf) test-peaks)
	(declare merge-peak-with-first)

	(defn concatenate-similar-peaks-xf []
	(fn [xf]
	(let [prev (volatile! ::none)]
	(fn
	([] (xf))
	([result] (xf result))
	([result input]
	(let [prior @prev]
	(vreset! prev input)
	(if (= (:type prior) (:type input))
	;;same type, merge the two peak-maps prior and input,
	;;else, keep processing
	(-> result
	pop ;; <-- !!! pop and conj are too specific functions that deal on collections.
	;; What should I do to make this work?
	(conj (merge-peak-with-first prior input)))
	(xf result input))))))))

	(defn merge-peak-with-first
	"Merges two peaks, the result will retain the values of p1 but:
	- :end_time will be become the value of p2
	- :peak will be the concat' value of p1 and p2"
	[p1 p2]
	(-> p1
	(update :peak
	(fn [p1-peak new-peak]
	(vec (concat p1-peak new-peak)))
	(:peak p2))
	(update :end-time
	(fn [_ new-end-time] new-end-time)
	(:end-time p2))))

	;; Usage below
	;; ===========
	(def test-peaks
	[{:type :a
	:peak [1 2]
	:end_time 1}
	{:type :a
	:peak [3 4]
	:end_time 2}
	{:type :a
	:peak [5 6]
	:end_time 3}
	{:type :b
	:peak []
	:end_time 8])

	;; I want the result to be:
	;; [{:type :a :peak [1 2 3 4 5 6] :end_time 3}
	;; {:type :b :peak [] :end_time 8}]
	(into [] (concatenate-similar-peaks-xf) test-peaks)