running elastic on mac: virtual memory areas vm.max_map_count [65530] is too low

Run terminal for docker (Docker terminal)

docker-machine ssh
sudo sysctl -w vm.max_map_count=262144
exit

clojure reducers are fast

(def v1 (for [x (range 10000000)]
          (rand-int 10000000)))

(count v1)

(require '[clojure.core.reducers])

(defn x-in-coll? [x coll]
  (clojure.core.reducers/reduce (fn [res next-v] (if (= next-v x) (reduced true) false)) false coll))

(defn x-in-coll2? [x coll]
  (some #(= x %) coll))

(time (x-in-coll? 0 v1))
(time (x-in-coll2? 0 v1))

(time (x-in-coll? 0 v1))
"Elapsed time: 176.250871 msecs"
=> false
(time (x-in-coll2? 0 v1))
"Elapsed time: 559.220763 msecs"
=> nil

netstat analog for mac os

lsof -iTCP -sTCP:LISTEN

lsof -iUDP

lsof -i4 -sTCP:LISTEN

lsof -i6 -sTCP:LISTEN

clojure.spec for any namespace on the fly

(create-ns 'com.mycompany)
(alias 'a 'com.mycompany)
(s/def ::a/keyword keyword?)
(s/exercise ::a/keyword)

java Date to LocalDate

(defn inst2local-date
  "convert java.util.Date to java.time.LocalDate"  [^Date date]
  (-> date .toInstant (.atZone (ZoneId/systemDefault)) .toLocalDate))

Joda to LocalDate in Clojure

(def joda-local-date (t/local-date-time year month day))

(-> joda-local-date tc/to-long Instant/ofEpochMilli (.atZone (ZoneId/systemDefault)) .toLocalDate)

clojurescript + reagent = track mouse example

Here is pretty simple example of mouse tracking app

(ns hello-world-cljs.core
  (:require [reagent.core :as r]))

(enable-console-print!)
(println "Hello App is started!")
;----------------------------------------------------------
(defonce app-state (r/atom {:mouse-trac? false :pointer {:x 0 :y 0}}))
;----------------------------------------------------------
(defn mouse-coords [e] {:x (.-pageX e) :y (.-pageY e)})
(defn mouse-handler [e] (swap! app-state assoc-in [:pointer] (mouse-coords e)))
(defn start-mouse-listen [handler] (js/document.addEventListener "mousemove" handler))
(defn stop-mouse-listen [handler] (js/document.removeEventListener "mousemove" handler))

;----------------------------------------------------------
(defn trac-mouse-button []
  [:div   [:button {:type "button" :class "btn btn-default" :on-click (fn [e] (swap! app-state update-in [:mouse-trac?] not))}
    "Mouse track?"]])

(defn trac-button-state-label [] [:div [:label (str (:mouse-trac? @app-state))]])

(defn mouse-coords-label [] [:div [:label (str "Pointer moved to: " (str (:pointer @app-state)))]])

(defn mouse-changer
  "this fn called every time when state of :mouse-trac? is changed"  []
  [:div   (if (:mouse-trac? @app-state)
     (start-mouse-listen mouse-handler)
     (stop-mouse-listen mouse-handler))])

(defn app-hello [] [:div [trac-mouse-button] [trac-button-state-label] [mouse-coords-label] [mouse-changer]])

(r/render-component [app-hello]
                    (.getElementById js/document "app"))

Here is result: