Better State Managment

A story on Functional Programming: how is it different and what benefits does it give to Object Oriented programmers.

Transcript

1. Better State Management video available at: http://vimeo.com/51528463
5. Why learn Functional Programming? 1. 2. 3.
6. Meeting Haskell
7. 1 2 3 4
8. 1 greet verb name = 2 verb ++ ", " ++ name ++ "!" 3 4 greet "Hello" "world" -- "hello, world!"
9. 6 pirateGreet = 7 8
10. 6 pirateGreet = greet "Arrrr" 7 8 pirateGreet "world" -- "Arrrr world!"
11. Ruby?
12. 1 greet = lambda do |verb, name| 2 "#{verb}, #{name}!" 3 end 4 5 6 7
13. 1 greet = lambda do |verb, name| 2 "#{verb}, #{name}!" 3 end 4 5 pGreet = greet.curry.('R') 6 7 pGreet.('world') # "R, world!"
14. 1 (\verb _ -> verb) "hi" "world" -- "hi"
15. 1 (\verb _ -> verb) "hi" "world" -- "hi"
16. 1 lambda do |verb, _| 2 verb 3 end.("hi", "world") # "hi"
17. 1 lambda do |verb, _| 2 verb 3 end.("hi", "world") # "hi"
18. map inject
21. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]]
22. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]] board[1][1] = "X"
23. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]] board[1][1] = "X" IMPOSSIBLE
24. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]] replace item index list =
25. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]] replace item index list = take index list ++ [item] ++ drop (index+1) list
26. board = [[Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing], [Nothing, Nothing, Nothing]] replace item index list = take index list ++ [item] ++ drop (index+1) list replace2d item x y matrix = ...
27. replace2d "x" 1 0 board
28. replace2d "o" 2 1 ( replace2d "x" 1 0 board )
29. replace2d "x" 0 1 ( replace2d "o" 2 1 ( replace2d "x" 1 0 board ) )
30. ... replace2d "x" 0 1 ( replace2d "o" 2 1 ( replace2d "x" 1 0 board ) )
31. 1 board.put_x(1,2) 2 3
32. 1 board.put_x(1,2) 2 board.put_o(0,1) 3
33. 1 board.put_x(1,2) 2 board.put_o(0,1) 3 board.put_x(2,1)
34. Imperative Programming 1 board.put_x(1,2) 2 board.put_o(0,1) 3 board.put_x(2,1)
35. ... replace2d "x" 0 1 ( replace2d "o" 2 1 ( replace2d "x" 1 0 board ) )
36. Functional Programming
37. Functional Programming is subset of Declarative Programming
38. replace item index list = take index list ++ [item] ++ drop (index+1) list Code mostly: • • • •
39. replace item index list = take index list ++ [item] ++ drop (index+1) list Code mostly: •Immutable • • •
40. replace item index list = take index list ++ [item] ++ drop (index+1) list Code mostly: •Immutable •Stateless • •
41. replace item index list = take index list ++ [item] ++ drop (index+1) list Code mostly: •Immutable •Stateless •Without side effects •
42. replace item index list = take index list ++ [item] ++ drop (index+1) list Code mostly: •Immutable •Stateless •Without side effects •Referentially transparent*
43. Imperative Declarative Ruby Haskell C
44. Why learn Functional Programming? 1. 2. 3.
45. Why learn Functional Programming? 1. 2. 3. To know Ruby better
46. Onto the web
47. Problems
48. New Player
49. New Player New Game New Move ...
50. New Player New Game New Move ... Database
51. New Player New Game New Move ... Database
52. New Player New Game New Move ... Database
53. New Player New Game New Move ... Database
54. New Player New Game New Move ... Database
55. New Player New Game New Move ... Database Still thinking with state.
56. New Player New Game New Move ...
57. New Player New Game New Move ... Session
58. New Player New Game New Move ... Session
59. New Player New Game New Move ... Session
60. New Player New Game New Move ... Session
61. New Player New Game New Move ... Session
62. New Player New Game New Move ... Session Still thinking with state.
63. Why learn Functional Programming? 1. 2. 3. To know Ruby better
64. Why learn Functional Programming? 1. 2. FP world needs heroes 3. To know Ruby better
65. New Player New Game New Move ...
66. existing data structure New Player New Game New Move ...
67. http://onezero.herokuapp.com
68. existing data structure New Player New Game New Move ...
69. existing data structure New Player New Game New Move ...
70. existing data structure New Player New Game New Move ...
71. existing data structure New Player New Game New Move ...
72. existing data structure New Player New Game New Move ... Still thinking with state.
75. ENO UGH
76. OF
77. THIS
78. TECHN OLOGY
79. PERIOD.
80. Back to Ruby
81. 1 class Square 2 3 4 def diagonal 5
82. 1 class Square 2 3 # what goes in -> 4 def diagonal 5
83. 1 class Square 2 3 # what goes in -> 4 def diagonal 5 # <- what is returned
84. 1 class Square 2 3 def render 4 buffer = RenderBuffer.current 5 buffer.move_to @position 6 # ...
85. 1 class Square 2 3 def render buffer 4 buffer.move_to @position 5 # ... 6
86. 1 class Square 2 3 def render buffer 4 buffer.move_to @position 5 # ... 6 Dependency Injection
87. 1 class Square 2 attr_accessible :width, :position, 3 :color, :border, :shadow 4 5 6
88. 1 class Square 2 attr_accessible :width, :position, 3 :style 4 5 class Style 6
89. 1 class Square 2 attr_accessible :width, :position, 3 :style 4 5 class Style 6 Single Responsibility Principle
90. Limit state • Split classes (domain / AR::Concerns) • Single-purpose wrappers (e.g. for session) • Limit singleton objects & static methods • ...
91. Why learn Functional Programming? 1. 2. FP world needs heroes 3. To know Ruby better
92. Why learn Functional Programming? 1. Better State Management 2. FP world needs heroes 3. To know Ruby better
93. Apology to Haskell
94. How to learn Haskell?
95. Learn you a Haskell for Great Good http://learnyouahaskell.com/
96. Yesod Web Framework http://yesodweb.com
97. Other Haskell resources contemplatecode.blogspot.com haskell.org github.com/nbartlomiej
98. “A large fraction of the flaws in software development are due to programmers not fully understanding all the possible states their code may execute in.” John Carmack, “Functional programming in C++”, 2012
99. Willard Van Orman Quine
100. The Scottish Parliament meets in the capital of Scotland.
101. The Scottish Parliament meets in Edinburgh.
102. Edinburgh has been the capital of Scotland since 1437.
103. Edinburgh has been Edinburgh since 1437.
105. Why learn Functional Programming? 1. Better State Management 2. FP world needs heroes 3. To know Ruby better
106. Images: stock.xching http://sxc.hu Edinburgh example: Prof. Uday S. Reddy http://stackoverflow.com/questions/210835/what-is-referential-transparency Sources
107. @nbartlomiej http://twitter.com/nbartlomiej , http://github.com/nbartlomiej www & blog: http://nbartlomiej.com Author