A survey build around Stuart Halloway's "4 pitches" for Clojure. Presented by Alan Dipert and Justin Kramer at BarCamp Rochester 2010

1. Clojure A Whirlwind Tour Alan Dipert, @alandipert Justin Kramer, @jkkramer

3. Functional

4. Tightly integrated with Java/C#

5. Dynamic

6. Built for concurrency

7. Two years old, at version 1.1

9. Functional programming

10. Java/C# interoperability

11. Language-level state support

13. Say a lot with a little. Less code, fewer bugs

14. Flexible, it becomes what you want

15. Code is data, “homoiconic”

17. Clojure Data Simple Data Compound Data “ 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”

20. Experimental programming and one-offs

22. Functions can be created dynamically

23. Functions can be stored just like other values, are “first class”

24. Functions can be passed to functions

25. Values are immutable

27. Immutable values combined with function composition make concurrency an easier nut to crack

29. Higher Order Functions A 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 Functions in 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)

32. Create classes that extend others, or implement interfaces

33. Instantiate object instances

34. Do lots of other, really cool things

36. You can program functionally and still take advantage of the Java ecosystem's huge library base

37. You can write homework 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 &quot;Sup!&quot;))

40. Mutable state sucks for sharing, i.e. for concurrency

44. Immutability (with Persistent Data Structures)

47. Clojure's way is to use red/black trees for complex data. Not constant time, but log32 n. Good enough.

48. Persistent Data Structures

53. Questions? Thanks! http://clojure.org