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Clojure
- 1. Clojure A WhirlwindTour Alan Dipert, @alandipert Justin Kramer, @jkkramer
- 2. Clojure is... ALisp dialect
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- 4. Tightly integrated withJava/C#
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- 7. Two years old,at version 1.1
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- 12. Why Lisp? Littlesyntax to learn
- 13. Say a lotwith a little. Less code, fewer bugs
- 14. Flexible, it becomeswhat you want
- 15. Code is data,“homoiconic”
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- 17. Clojure Data SimpleData Compound Data \a “ house” 42 [1 2 3 4] true (true false true) :fname {:fname “Alan” :lname “Dipert} 7/8 #{“bar” “camp” “rules”}
- 18. Expressions 34 34(+ 1 2) 1 + 2 (println (str “The date is ” (new Date))) println(str(“The date is”, new Date)) (def X 7) X = 7 (< 7 8 9) (7 < 8) && (8 < 9) (if (< X 8) “less than 8” “at least 8”) X < 8 ? “less than 8” : “at least 8”
- 19. Evaluation and theREPL Enter one command at a time
- 20. Experimental programming andone-offs
- 21. Functional Programming Aprogramming paradigm, set of language features
- 22. Functions can becreated dynamically
- 23. Functions can bestored just like other values, are “first class”
- 24. Functions can bepassed to functions
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- 26. Why Functional Programming?Functions are dependable building blocks Especially when they're “side-effect free” Function composition is a powerful modularization technique
- 27. Immutable values combinedwith function composition make concurrency an easier nut to crack
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- 29. Higher Order FunctionsA higher order function is a function that takes one or more other functions as arguments. map, select, filter, reject, reduce, foldl, inject, fold...
- 30. Higher Order Functionsin Action (map (fn [x] (+ x 1)) [1 2 3 4]) ;; (map inc ...) [2 3 4 5] (filter odd? (range 10)) (1 3 5 7 9) (every? odd? [1 3 5 7 9]) true (reduce + [1 2 3]) 6 (drop-while even? [2 4 8 9 13 43]) (9 13 43) (take-while #(< % 10) [1 3 11 42 102]) (1 3)
- 31. Java/C# Interoperability Clojureruns on both the JVM and CLR It's easy to create, call, and interact with objects (arguably easier than it is in Java itself!) Clojure lets you: Call static methods
- 32. Create classes thatextend others, or implement interfaces
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- 34. Do lots ofother, really cool things
- 35. Java/C# Interoperability Withthe power of Lisp, you can cleanly abstract away common OOP patterns using Lisp's macro system
- 36. You can programfunctionally and still take advantage of the Java ecosystem's huge library base
- 37. You can writehomework assignments in Clojure and hand your professor a .jar
- 38. Java/C# Interoperability (every?#(Character/isWhitespace) “hallo”) ;; false (every? #(Character/isWhitespace) “ “) ;; true (. javax.swing.JOptionPane (showMessageDialog nil "Sup!"))
- 39. State The problemof concurrency is really one of state .
- 40. Mutable state sucksfor sharing, i.e. for concurrency
- 41. Managing state inOOP is too complex “Stop the world while I look at it” We need reliable building blocks
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- 43. State Clojure givesus better tools: Pure Functions
- 44. Immutability (with PersistentData Structures)
- 45. Managed state transitionValue, identity, state
- 46. Persistent Data StructuresImmutability is traditionally expensive One way is to make copies of data structures, which is slow.
- 47. Clojure's way isto use red/black trees for complex data. Not constant time, but log32 n. Good enough.
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- 49. State Snapshots vs.“Stop the World”
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- 51. Refs (STM –transactions) Bank account transfer Agents
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