![Higher-Order Functions ;; integer as first class value (def a 10) ;; function as first class value (def b (fn [x] (+ x a))) ;; anonymous function #(+ a %) ;; function that generate a closure (def c (fn [x] #(+ x %))) ;; high order function (function as parameter) (def d (fn [f x] (f x a)))](https://image.slidesharecdn.com/clojure-slides-111128011440-phpapp02/85/Clojure-Practical-functional-approach-on-JVM-29-320.jpg)
![Functional Programming Side-Effect-Free Functions ;; function that free of side effect (defn f [x] (+ x 1000)) ;; function with side effect (defn f [x] (println (str “logging: x=” x)) (+ x 1000)) ;; I/O operations are side effect (defn dump [writer data] (.write writer data))](https://image.slidesharecdn.com/clojure-slides-111128011440-phpapp02/85/Clojure-Practical-functional-approach-on-JVM-30-320.jpg)
![Functional Programming Recursion Recursive Looping public int sumAll(int n) { int i = 1, s = 0; while(i <= n) { s = s + i; i++; } return s; } public int sumAll(int n) { if ( n > 0){ return n + sumAll(n-1); } else { return 0; } } (defn sum-all [n] (if (> n 0) (+ n (sum-all (dec n))) 0)) (defn sum-all2 [n s] (if (> n 0) ( recur (dec n) (+ n s)) s)) (defn sum-all [n] (sum-all2 n 0)) java.lang.StackOverflowError Tail recursion](https://image.slidesharecdn.com/clojure-slides-111128011440-phpapp02/85/Clojure-Practical-functional-approach-on-JVM-31-320.jpg)
![Functional Programming Lazy Evaluation ;; define data (def data [1 2 3 4 5]) ;; a function with side effect (defn side-effect-inc [i] (println i) (inc i)) ;; create lazy sequence with map (def lazy-data (map side-effect-inc data)) ;; consume first 2 items for lazy sequence (take 2 lazy-data) (1 2 3 4 5 2 3) (take 5 (range)) (take 5 (repeat “a”))](https://image.slidesharecdn.com/clojure-slides-111128011440-phpapp02/85/Clojure-Practical-functional-approach-on-JVM-32-320.jpg)
![Collections Vector: [1 2 3]](https://image.slidesharecdn.com/clojure-slides-111128011440-phpapp02/85/Clojure-Practical-functional-approach-on-JVM-46-320.jpg)
Clojure: Practical functional approach on JVM
- 2. Clojure Practical Functional Approach on JVM Sun Ning 2011.11.28
- 3. Agenda Introduction to Clojure
- 7. Introduction to Clojure Functional Programming
- 8. Lisp Syntax
- 10. Macro
- 11. Java Interop
- 12. Introduction to Clojure Functional Programming
- 13. Lisp Syntax
- 14. State Management
- 15. Macro
- 16. Java Interop
- 17. Functional Programming Avoiding Mutable State
- 18. Functions as First-Class Values
- 22. Recursion
- 23. Lazy vs. Eager Evaluation
- 24. Declarative vs. Imperative Programming
- 25. Functional Programming Avoiding Mutable State Better concurrency (no need for locking)
- 26. Persistent data structure zs = xs + ys
- 27. Functional Programming Functions as First-Class Values
- 29. Higher-Order Functions ;; integer as first class value (def a 10) ;; function as first class value (def b (fn [x] (+ x a))) ;; anonymous function #(+ a %) ;; function that generate a closure (def c (fn [x] #(+ x %))) ;; high order function (function as parameter) (def d (fn [f x] (f x a)))
- 30. Functional Programming Side-Effect-Free Functions ;; function that free of side effect (defn f [x] (+ x 1000)) ;; function with side effect (defn f [x] (println (str “logging: x=” x)) (+ x 1000)) ;; I/O operations are side effect (defn dump [writer data] (.write writer data))
- 31. Functional Programming Recursion Recursive Looping public int sumAll(int n) { int i = 1, s = 0; while(i <= n) { s = s + i; i++; } return s; } public int sumAll(int n) { if ( n > 0){ return n + sumAll(n-1); } else { return 0; } } (defn sum-all [n] (if (> n 0) (+ n (sum-all (dec n))) 0)) (defn sum-all2 [n s] (if (> n 0) ( recur (dec n) (+ n s)) s)) (defn sum-all [n] (sum-all2 n 0)) java.lang.StackOverflowError Tail recursion
- 32. Functional Programming Lazy Evaluation ;; define data (def data [1 2 3 4 5]) ;; a function with side effect (defn side-effect-inc [i] (println i) (inc i)) ;; create lazy sequence with map (def lazy-data (map side-effect-inc data)) ;; consume first 2 items for lazy sequence (take 2 lazy-data) (1 2 3 4 5 2 3) (take 5 (range)) (take 5 (repeat “a”))
- 33. Functional Programming Declarative Programming DSL (cd "/home/login" (path "/home/login/bin" (run "clojure"))) (cd "/home/login" (path "/home/login/bin" (env "JAVA_OPTS" "-XMaxPermSize=128m" (run "ant compile"))))
- 34. Introduction to Clojure Functional Programming
- 35. Lisp Syntax
- 36. State Management
- 37. Macro
- 38. Java Interop
- 39. Syntax Symbol: user/m
- 40. Character: \a
- 41. Integer: 1 2 3
- 42. String: “hello”
- 43. Keyword: :world
- 44. Boolean: true
- 45. Null: nil
- 46. Collections Vector: [1 2 3]
- 47. List: (1 2 3)
- 48. Set: #{1 2 3}
- 49. Map: {:a 1 :b 2}
- 50. (def a 12)
- 51. (def b “tomcat”)
- 52. (def c (fn [x y] (+ x y)))
- 53. (def c #(+ %1 %2))
- 54. (defn c [x y] (+ x y))
- 55. Introduction to Clojure Functional Programming
- 56. Lisp Syntax
- 57. State Management
- 58. Macro
- 59. Java Interop
- 60. State management Coordinated vs. Independent State Coordinated updates can’t just take one identity into account—they have to manage the states of several interdependent identities to ensure that they are all updated at the same time and that none are left out. Synchronous vs. Asynchronous Updates
- 61. State management Ref - Synchronous, Coordinated
- 62. Atom – Synchronous, Independent
- 64. Vars – Thread local values
- 65. State management ;;refs and STM (def a (ref 0)) (def b (ref 1)) (dosync (alter a inc) (alter b + @a)) @a @b ;;atoms (def a (atom 0)) (def b (atom 1)) (swap! a inc) (swap! b + @a) @a @b ;;agents (def a (agent 0)) (def b (agent 1)) (send a inc) (send b + @a) ;;thread local binding (def a 0) (def b 1) (binding [a 100] (+ b a)) a
- 66. STM Multiple version concurrent control Each transaction gets its own view of the data that it’s interested in.
- 67. Each transaction merrily chugs along making changes to in-transaction values only.
- 68. Examine the refs against the modification target for conflicts.
- 69. Commit changes or Retry
- 70. Introduction to Clojure Functional Programming
- 71. Lisp Syntax
- 72. State Management
- 73. Macro
- 74. Java Interop
- 75. Macro Write code that writes code
- 76. Macro (defmacro cd "change current directory" [path & cmd] `(str "cd " ~path "; " ~ @cmd) ) (defmacro run "simply run a command" [cmd] `(str ~cmd "; ") )
- 77. Macro (cd “/home/nsun” (run “rm -rf ./*”)) cd /home/nsun; rm -rf ./*; (macroexpand '(cd "/home/nsum" (run "rm -rf ./*"))) (clojure.core/str "cd " "/home/nsum" "; " (run "rm -rf ./*"))
- 78. Introduction to Clojure Functional Programming
- 79. Lisp Syntax
- 80. State Management
- 81. Macro
- 82. Java Interop
- 83. Java Interop – Java for Clojure (import java.util.Date) (def now (Date.)) (.getTime now) (System/currentTimeMillis)
- 84. Java Interop - Clojure->Java (ns gen-class-test.core (:gen-class :state value :init init :constructors {[String] []} :methods [[printValue [String] void] ^{:static true} [version [] String]])) (defn version [] "1.0") (defn -init [name] [[] (atom {:name name})]) (defn -printValue [this prefix] (println (str prefix @(.value this))))
- 85. Real World Clojure where functional programming landed
- 86. Real World Clojure Network programming
- 87. Web development
- 88. Databases
- 89. Network Programming Aleph – network programming framework (HTTP/TCP/UDP)
- 90. Lamina – Abstraction of Queue
- 91. Gloss – Abstraction of bytes protocol
- 92. Based on Netty
- 93. Aleph (defcodec dummy-codec (finite-frame :int24 (string :utf8))) (defn echo-handler [ch client-info] (receive-all ch #(do (println %) (enqueue ch %)))) (start-tcp-server echo-handler {:port 1234, :frame dummy-codec}) Gloss codec Lamina queue Aleph
- 94. Web Development Web handler abstraction Ring (Similar to WSGI, Rack) Web frameworks Compojure
- 95. Noir
- 96. Ring (defn app [req] {:status 200 :headers {"Content-Type" "text/html"} :body "Hello World from Ring"}) Middleware Middleware Middleware Handler Middleware
- 97. Compojure framework (defroutes default-routes (GET "/rage/:id" [] get-rage) (GET "/rages/:channel" [] get-rages)) (defn get-rage [req] (let [id (:id (:params req))] (json-response (get-data id)))) (defroutes default-routes (GET "/rage/:id" [] get-rage) (GET "/rages/:channel" [] get-rages))
- 98. Clojure JDBC DDL ;; database config (def db {:classname "org.hsqldb.jdbc.JDBCDriver" :subprotocol "hsqldb" :subname "testdb" :user "SA" :password ""}) (defn create-db [] (jdbc/with-connection db (jdbc/create-table table-name [:name "VARCHAR(32)" "PRIMARY KEY"] [:submitter "VARCHAR(32)"] [:title "VARCHAR(512)"])))
- 99. Clojure JDBC DML (jdbc/with-connection db (jdbc/with-query-results results [(str "select * from " (name table-name))] (into [] results)))
- 100. Clojure People Meet clojure hackers on github
- 101. @richhickey Creator of clojure
- 102. Presentations: Simple made Easy
- 104. @fogus Clojure and ClojureScript core developers
- 105. Author of “The Joy of Clojure”
- 107. @nathanmarz Leader engineer of backtype (acquired by twitter)
- 108. Creator of Storm (realtime computation framework)
- 109. Cascalog (clojure query language on hadoop)
- 111. Author of Ring spec
- 112. Author of Clj-redis
- 113. Clj-http
- 114. Clj-stacktrace
- 115. ...
- 117. Emacs hacker Author of emacs-starter-kit Author of leiningen (clojure build tool)
- 118. @Raynes 17 years old Clojure guy
- 119. co-developer of Clojail
- 120. tryclj.com Clojure community and me
- 121. Many more @ztellman (Aleph, Lamina, Gloss)
- 122. @ibdknox (Noir, Korma, I Will Build Your Prototype )
- 125. @cemerick (O'Reilly Clojure Programming)
- 126. @stuarthalloway (Pragmatic Programming Clojure)
- 127. @stuartsierra (Clojure core developer, Apress Practical Clojure)
- 128. Q&A
- 129. Thanks