├── .gitignore
├── project.clj
├── README.md
├── src
    └── core_async_patterns
    │   └── core.clj
└── LICENSE


/.gitignore:
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 1 | /target
 2 | /classes
 3 | /checkouts
 4 | pom.xml
 5 | pom.xml.asc
 6 | *.jar
 7 | *.class
 8 | /.lein-*
 9 | /.nrepl-port
10 | .hgignore
11 | .hg/
12 | 


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/project.clj:
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1 | (defproject core-async-patterns "0.1.0-SNAPSHOT"
2 |   :description "Example patterns for using clojure.core.async"
3 |   :url "https://purelyfunctional.tv/core-async-patterns"
4 |   :license {:name "CC0 1.0 Universal (CC0 1.0) Public Domain Dedication"
5 |             :url "http://creativecommons.org/publicdomain/zero/1.0/"}
6 |   :dependencies [[org.clojure/clojure "1.10.0"]
7 |                  [org.clojure/core.async "0.4.490"]])
8 | 


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/README.md:
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 1 | # core-async-patterns
 2 | 
 3 | Code to accompany the [Clojure core.async Patterns course][patterns],
 4 | part of [PurelyFunctional.tv Online Mentoring][mentoring].
 5 | 
 6 | [patterns]: https://purelyfunctional.tv/courses/core-async-patterns
 7 | [mentoring]: https://purelyfunctional.tv/
 8 | 
 9 | ## License
10 | 
11 | [![CC0](http://i.creativecommons.org/p/zero/1.0/88x31.png)](http://creativecommons.org/publicdomain/zero/1.0/)
12 | 
13 | To the extent possible under law, the person who associated CC0 with
14 | this work has waived all copyright and related or neighboring rights
15 | to the code in this repository.
16 | 
17 | See the `LICENSE` file for more information.
18 | 


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/src/core_async_patterns/core.clj:
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  1 | (ns core-async-patterns.core
  2 |   (:require [clojure.core.async :as async])
  3 |   (:require [clojure.test :refer [deftest is]]))
  4 | 
  5 | ;; Take with timeout
  6 | (defn take-with-timeout!! [c t]
  7 |   (first (async/alts!! [c (async/timeout t)] :priority true)))
  8 | (defn take-with-timeout! [c t]
  9 |   (async/go
 10 |     (first (async/alts! [c (async/timeout t)] :priority true))))
 11 | 
 12 | ;; Put with timeout
 13 | (defn put-with-timeout!! [c v t]
 14 |   (first (async/alts!! [[c v] (async/timeout t)] :priority true)))
 15 | (defn put-with-timeout! [c v t]
 16 |   (async/go
 17 |     (first (async/alts! [[c v] (async/timeout t)] :priority true))))
 18 | 
 19 | ;; Go Throw
 20 | (defmacro <?! [c]
 21 |   `(let [[op# v#] (async/<! c)]
 22 |      (case op#
 23 |        :return v#
 24 |        :throw (throw v#))))
 25 | (defn <?!! [c]
 26 |   (let [[op v] (async/<!! c)]
 27 |     (case op
 28 |       :return v
 29 |       :throw (throw v))))
 30 | (defmacro go-throw [& body]
 31 |   `(async/go
 32 |      (try
 33 |        (let [ret# (do ~@body)]
 34 |          [:return ret#])
 35 |        (catch Throwable t#
 36 |          [:throw t#]))))
 37 | 
 38 | ;; Thread pool
 39 | (def work (async/chan))
 40 | (doseq [x 10]
 41 |   (async/thread
 42 |     (loop []
 43 |       (let [v (async/<!! work)]
 44 |         (try
 45 |           (handle v)
 46 |           (catch Throwable t
 47 |             (println t))))
 48 |       (recur))))
 49 | 
 50 | ;; Backpressure
 51 | (def requests (async/chan))
 52 | (def backpressure (async/chan 1000))
 53 | (async/go
 54 |   (loop []
 55 |     (let [r (async/<! requests)
 56 |           [v] (async/alts! [[backpressure r]] :default ::not-ready)]
 57 |       (when (= v ::not-ready)
 58 |         (respond-not-ready r)))
 59 |     (recur)))
 60 | (async/go
 61 |   (doseq [x 10]
 62 |     (async/thread
 63 |       (loop []
 64 |         (let [r (async/<!! backpressure)]
 65 |           (handle r)
 66 |           (recur))))))
 67 | 
 68 | ;; Kill switch
 69 | (def kill-switch (async/chan))
 70 | (async/thread
 71 |   (loop []
 72 |     (let [[v] (async/alts!! [kill-switch] :default :continue)]
 73 |       (when (= v :continue)
 74 |         (do-something)
 75 |         (recur)))))
 76 | (defn kill-thread []
 77 |   (async/close! kill-switch))
 78 | 
 79 | ;; Poison pill
 80 | (def work (async/chan))
 81 | (async/go
 82 |   (loop []
 83 |     (let [v (async/<! work)]
 84 |       (when (not= :poison v)
 85 |         (do-work v)
 86 |         (recur)))))
 87 | (defn kill-go-block []
 88 |   (async/put! work :poison))
 89 | 
 90 | ;; Start latch
 91 | (def latch (async/chan))
 92 | (dotimes [x 1000]
 93 |   (async/go
 94 |     (async/<! latch)
 95 |     (do-something)))
 96 | (async/close! latch)
 97 | 
 98 | ;; Token bucket
 99 | (def bucket (async/chan (async/dropping-buffer 10)))
100 | (async/go
101 |   (loop []
102 |     (async/put! bucket :token)
103 |     (async/<! (async/timeout 1000))
104 |     (recur)))
105 | (defn api-request [url]
106 |   (async/<!! bucket)
107 |   (get-request url))
108 | 
109 | 
110 | 
111 | 
112 | 
113 | 
114 | 
115 | 
116 | 
117 | 
118 | 
119 | 
120 | 
121 | 
122 | (def cache (atom :cached))
123 | 
124 | (defn request-value []
125 |   (let [c (async/chan 10)]
126 |     (async/go
127 |       (loop []
128 |         (let [v (get-request "http://lispcast.com/")]
129 |           (reset! cache v)
130 |           (async/put! c v))
131 |         (async/<! (async/timeout 10000))
132 |         (recur)))
133 |     (async/put! c @cache)
134 |     c))
135 | 
136 | (def current (atom :waiting))
137 | (let [c (request-value)]
138 |   (async/go
139 |     (loop []
140 |       (let [v (async/<! c)]
141 |         (reset! current v))
142 |       (recur))))
143 | 
144 | 
145 | 
146 | 
147 | 
148 | 
149 | 
150 | 
151 | 
152 | 
153 | 
154 | 
155 | 
156 | 


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