core_async_playground.clj

(require '[clojure.core.async :as async :refer :all])

(defn fake-search [kind]
  (fn [query]
    (Thread/sleep (int (* (java.lang.Math/random) 1000)))
    (str kind " result for " query)))

(def web (fake-search "Web"))
(def image (fake-search "Image"))
(def video (fake-search "Video"))

;; Google search 2.0
;; http://talks.golang.org/2012/concurrency.slide#46

(defn google2-0 [query]
  (let [c (chan)]
    (go (>! c (web query)))
    (go (>! c (image query)))
    (go (>! c (video query)))
    (reduce (fn [results _]
              (conj results (<!! (go (<! c)))))
            []
            (range 3))))

(google2-0 "Clojure")

;; Google search 2.1
;; http://talks.golang.org/2012/concurrency.slide#47

(defn google2-1 [query]
  (let [c (chan)
        t (timeout 500)]
    (go (>! c (web query)))
    (go (>! c (image query)))
    (go (>! c (video query)))
    
    (reduce (fn [results _]
              (conj results (first (alts!! [c t]))))
            []
            (range 3))))


(google2-1 "Clojure")