Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/11Ojtbq. David Nolen introduces Om, a ClojureScript library providing a functional layer on top of Facebook React for building MVC UIs. Filmed at qconnewyork.com. David Nolen is a JavaScript developer for Cognitect. He also runs a Brooklyn based workshop called Kitchen Table Coders. In his free time he does fun stuff with Clojure and ClojureScript.

1. Immutability,
or Putting the Dream Machine to Work

2. Watch the video with slide
synchronization on InfoQ.com!
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/om-clojurescript
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7. The trie memory scheme is inefficient for small memories, but it
be- comes increasingly efficient in using available storage space as
memory size increases. The attractive features of the scheme are
these: 1) The retrieval process is extremely simple. Given the
argument, enter the standard ini- tial register with the first
character, and pick up the address of the second. Then go to the
second register, and pick up the address of the third, etc. 2) If two
arguments have initial characters in common, they use the same
storage space for those characters.
-J.C.R. Licklider, "Man-Computer Symbiosis" 1960

13. Model-View-Controller

14. ๏ first formulated by Trygve Reenskaug
Adele Goldberg and others at Xerox
PARC in 1979
๏ long shadow, the basic concepts still
prevalent today.

15. ๏ At a very abstract level MVC is a sound
separation of concerns
๏ Implementations leave much to be
desired
๏ Stateful objects everywhere

18. Functional Programming and Data
• immutable values, not mutable objects
• “change” returns a new value, leaving the old one unmodified
• they’re persistent
• they’re fast

19. Simple example: Linked List
X

20. Simple example: Linked List
Y X

21. Simple example: Linked List
X
Z
Y

22. Simple example: Linked List
X
Z
Y
structural sharing

23. Sharing structure
• space efficiency
• computational efficiency – avoids copying

24. Phil Bagwell
• Array Mapped Trie
• Hash Array Mapped Trie

25. Bitmapped Vector Trie
• data lives in the leaves
• e.g. prefix tree used for string lookup
• bitwise trie

26. Persistent Vector

27. Persistent Vector

28. Persistent Vector

29. Persistent Vector

30. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

31. Persistent Vector
getindex

32. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

33. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
0b01101010

34. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
0b01101010

35. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
0b01101010

36. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
0b01101010

37. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
0b01101010

38. Persistent Vector
assoc

39. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

40. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

41. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

42. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

43. Persistent Vector
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
104 105 foo 107

44. Persistent Vector
Length 4 internal vectors?

45. Persistent Vector
32
From Bagwell, Rompf 2011

46. 327

47. 34,359,738,368
elements

48. demo

52. Om

54. f(D0) = V0

55. f(D1) = V1

56. diff(V0,V1) = CHANGES

58. demo

60. Persistent Data Structures … ROCK

62. Questions?

63. Watch the video with slide synchronization on
InfoQ.com!
http://www.infoq.com/presentations/om-clojurescript