Clojure's Reference Types

A short introduction to Clojure's reference types that I gave to the Clojure Toronto meetup.

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
15. IDENTITY ≠ STATE
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!