core.async example: Ping Pong

ping-pong.cljs

(defn player
  [msg table]
  (go (loop []
        (let [ball (<! table)]                    ;; the ball was hit to this player
          (.log js/console msg)
          (<! (timeout 100))                      ;; wait 100msecs
          (>! table (update-in ball [:hits] inc)) ;; hit the ball back
          (recur)))))

(defn game
  [table ball]
  (go (do (.log js/console "Game started.")
          (>! table ball)                         ;; put the ball into play
          (<! (timeout 1000))                     ;; game lasts for ten seconds
          (<! table)                              ;; take the ball out of play (fun police)
          (.log js/console "Game ended."))))

(defn ping-pong!
  []
  (let [table (chan)
        ball  {:hits 0}]
    (player "ping" table)                         ;; start a player process that pings
    (player "pong" table)                         ;; start a player process that pongs
    (game table ball)))                           ;; start the game process