Clojure's Reference Types

Transcript

1. NATE SMITH @nwjsmith theinternate.com

2. Clojure's REFERENCE TYPES

3. ATOMS AGENTS REFS

4. VARS

5. (def wayne-gretzky {:number 99 :position "C" :goals 45}) wayne-gretzky ;;

   => {:number 99 :position "C" :goals 45}

6. wayne_gretzky = { number: 99, position: "C", goals: 45 }

7. (def wayne-gretzky {:number 99 :position "C" :goals 45}) (defn score

   [player] (update-in player [:goals] inc))

8. wayne-gretzky ;; => {:number 99 :position "C" :goals 45} (score

   wayne-gretzky) ;; => {:number 99 :position "C" :goals 46}

9. wayne-gretzky ;; => {:number 99 :position "C" :goals 45} (score

   wayne-gretzky) ;; => {:number 99 :position "C" :goals 46} wayne-gretzky ;; => {:number 99 :position "C" :goals 45}

10. IDENTITY and STATE

11. None
12. None
13. None
14. None

15. IDENTITY ≠ STATE

16. None
17. None

18. BOTH MICHAEL JACKSON

19. WHAT CHANGED?

20. HIS IDENTITY

21. STATE IS IMMUTABLE, IDENTITIES CHANGE

22. wayne_gretzky = { number: 99, position: "C", goals: 45 }

    wayne_gretzky[:goals] += 1 wayne_gretzky # => { number: 99, position: "C", goals: 46 }

23. ATOMS AGENTS REFS

24. ATOMS

25. (def atomic-wayne-gretzky (atom {:position "C" :number 99 :goals 0})) (deref

    atomic-wayne-gretzky) ;; => {:position "C" :number 99 :goals 0} @atomic-wayne-gretzky ;; => {:position "C" :number 99 :goals 0}

26. (def atomic-wayne-gretzky (atom {:position "C" :number 99 :goals 0})) (dothreads!

    (fn [] (swap! atomic-wayne-gretzky score)) :threads 100 :times 100) @atomic-wayne-gretzky ;; => {:position "C" :number 99 :goals 10000}

27. AGENTS

28. (def agent-gretzky (agent {:position "C" :number 99 :goals 0})) @agent-gretzky

    ;; => {:position "C" :number 99 :goals 0}

29. (defn score-slowly [player] (Thread/sleep 5000) (update-in player [:goals] inc)) (send

    agent-gretzky score-slowly) @agent-gretzky ;; => {:position "C" :number 99 :goals 0} @agent-gretzky ;; => {:position "C" :number 99 :goals 0} ;; 5 seconds later... @agent-gretzky ;; => {:position "C" :number 99 :goals 1}

30. REFS

31. THEY'RE FRIGGIN' MAGIC

32. (def gretzky-curr (ref {:position "C" :number 99 :goals 0})) (def

    gretzky-prev (ref @gretzky-curr)) @gretzky-curr ;; => {:position "C" :number 99 :goals 0} @gretzky-prev ;; => {:position "C" :number 99 :goals 0}

33. (dothreads! (fn [] (dosync (ref-set gretzky-prev @gretzky-curr) (alter gretzky-curr score)))

    :threads 100 :times 100) @gretzky-prev ;; => {:position "C" :number 99 :goals 9999} @gretzky-curr ;; => {:position "C" :number 99 :goals 10000}

34. Atoms: independent, synchronous Agents: independent, asynchronous Refs: coordinated, synchronous

35. THANKS!

36. None