chpill

/**
 * The first commented line is your dabblet’s title
 */

background: #fff;

chpill

(defn error? [x] (:error x))

(defn original [chunks]
  (transduce (comp
              (halt-when error?)
              (map #(frequencies (map :a %))))
             (completing (partial merge-with +))
             {}
             chunks))

chpill

(defn make-chunks [chunk-count chunk-size]
  (for [i (range chunk-count)]
    (for [j (range chunk-size)]
         {:a (mod j 3)})))

(def chunks (make-chunks 10 999))

chpill

(require '[net.cgrand.xforms :as x])

(defn using-xforms [chunks]
  (into {}
        (comp (halt-when error?)
              cat
              (x/by-key :a x/count))
        chunks))

(using-xforms chunks)

chpill

(def mini-chunks-with-error
  [[{:a 0} {:a 1} {:a 2}]
   [{:a 0} {:a 1} {:a 2}]
   {:error "Something terrible has happened!"}])

(original mini-chunks-with-error)
=> {:error "Something terrible has happened!"}

(using-xform mini-chunks-with-error)
=> Unhandled java.lang.ClassCastException

chpill

(original chunks)
=> {0 3330, 1 3330, 2 3330} ;; as expected!

;; Note that the standard deviation is huge here
(criterium/quick-bench (original chunks))
"
Evaluation count              : 294 in 6 samples of 49 calls.
Execution time mean           : 10.778696 ms
Execution time std-deviation  : 8.818884 ms
Execution time lower quantile : 1.680341 ms ( 2.5%)

chpill

([to xform from]
 (if (instance? clojure.lang.IEditableCollection to)
  (with-meta 
    (persistent! (transduce xform conj! (transient to) from))
    (meta to))
  (transduce xform conj to from)))

chpill

(defn using-xform--improved [chunks]
  (transduce (comp (halt-when error?)
                   cat
                   (x/by-key :a x/count))
             conj
             {}
             chunks))

(using-xform--improved chunks)
=> {0 3330, 1 3330, 2 3330} ;; Still works

chpill

(defn single-return-transducer
  "Dummy transducer that simply returns the value given to it,
  ignoring any accumulated value"
  ([] :initial-value-to-be-ignored)
  ([final-value] final-value)
  ([initial-value v] v))

(defn using-xform--hazard-edition [chunks]
  (transduce (comp (halt-when error?)
                   cat

chpill

(ns remux.core)

(defn create-store [handlers initial-state]
  (let [state (atom initial-state)
        dispatching? (atom false)]
    {::state state
     ::get-state (fn get-state [] @state)
     ::get-raw-state #(state)
     ::dispatch
     (fn [action-name data]