Pivorak Clojure by Dmytro Bignyak
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(1) Clojure is a functional programming language that uses parentheses syntax and runs on the JVM; (2) It has features like immutability, concurrency constructs like atoms and agents, and support for functional programming patterns; (3) Clojure can be used for both functional programming and object-oriented programming with records, and has tools for metaprogramming, async programming with core.async, and compiling to JavaScript with ClojureScript.
![Is that easy?
(defn select
"Returns a set of the elements for which pred is true"
{:added "1.0"}
[pred xset]
(reduce (fn [s k] (if (pred k) s (disj s k)))
xset xset))](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-6-320.jpg)
![• Clojure can used as functional style
(map (partial * 10) [1 2 3]) ; => [10 20 30]
• It also can be used for structures
(defrecord Color [red green blue])
(def b (assoc a :alpha 0.1))
; b => {:alpha 0.1, :red 0.5 :green 0.6, :blue 0.7}](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-9-320.jpg)
![atom
(let [x (atom 0)]
(println @x) ; => 0
(swap! x inc)
(println @x)) ; => 1](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-13-320.jpg)
![agent
(def a (agent 0)) ; initial state
(send a inc)
(println @a) ; => 1
(send a (fn [x] (Thread/sleep 100) (inc x)))
(println @a) ; => 1
; in 100ms
(println @a) ; => 2](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-14-320.jpg)
![Example core.async
(defonce log-chan (chan))
(defn loop-worker [msg]
(println msg))
(go-loop []
(let [msg (<! log-chan)]
(loop-worker msg)
(recur)))](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-18-320.jpg)
![Clojure (as all Lisps) is very
powerful in metaprogramming
(defmacro unless [pred a b]
`(if (not ~pred)
~a
~b))
(unless (> 1 10)
(println "1 > 10. ok")
(println "1 < 10. wat"))](https://image.slidesharecdn.com/pivorak-161125112042/85/Pivorak-Clojure-by-Dmytro-Bignyak-19-320.jpg)
Pivorak Clojure by Dmytro Bignyak
- 1. Clojure )))) How not to be afraid of parentheses Dmytro Bignyak
- 2. Me Dmytro Bignyak GitHub: deril Twitter: @derilok
- 3. It is not about • in Ruby it takes 5 lines of code but in Clojure only 4 • I show you much code, how cool Clojure is
- 5. I ♥ Clojure
- 6. Is that easy? (defn select "Returns a set of the elements for which pred is true" {:added "1.0"} [pred xset] (reduce (fn [s k] (if (pred k) s (disj s k))) xset xset))
- 8. • It is a functional language • It has functional advantages
- 9. • Clojure can used as functional style (map (partial * 10) [1 2 3]) ; => [10 20 30] • It also can be used for structures (defrecord Color [red green blue]) (def b (assoc a :alpha 0.1)) ; b => {:alpha 0.1, :red 0.5 :green 0.6, :blue 0.7}
- 10. Clojure is very useful when you want some ASYNC
- 11. Clojure has 4 types of links 1. var (thread local) 2. atom (can be synchronically changed, but not coordinately) 3. agent (async state; analogue actor) 4. ref (can be synchronically and coordinately changed)
- 12. var (def a 123) (println a) ; => 123
- 13. atom (let [x (atom 0)] (println @x) ; => 0 (swap! x inc) (println @x)) ; => 1
- 14. agent (def a (agent 0)) ; initial state (send a inc) (println @a) ; => 1 (send a (fn [x] (Thread/sleep 100) (inc x))) (println @a) ; => 1 ; in 100ms (println @a) ; => 2
- 15. • Agents change their state asynchronically • In any time you can call deref and get the state of agent
- 16. Clojure can be used for MVCC (Multiversion Concurrency Control) (def account1 (ref 100) (def account2 (ref 0)) (dosync (alter account1 - 30) (alter account2 + 30)) (println @account1) ; => 70 (println @account2) ; => 30 (dosync (alter account1 * 0) (alter account2 / 0)) ; => ArithmeticException ; values weren’t changed (println @account1) ; => 70 (println @account2) ; => 30
- 18. Example core.async (defonce log-chan (chan)) (defn loop-worker [msg] (println msg)) (go-loop [] (let [msg (<! log-chan)] (loop-worker msg) (recur)))
- 19. Clojure (as all Lisps) is very powerful in metaprogramming (defmacro unless [pred a b] `(if (not ~pred) ~a ~b)) (unless (> 1 10) (println "1 > 10. ok") (println "1 < 10. wat"))
- 20. Language is nothing without infrastructure
- 21. • Clojure uses JVM • Eclipse, IDEA plugins • Leiningen building tool • Web frameworks (LuminusWeb, Noir) • Async servers (https://github.com/ztellman/aleph)
- 23. What’s next?