James Majors: What the Swiftly Func?

Transcript

1. Thanks! http://bit.ly/AltConf2017

2. This presentation doesn't contain any confidential information and isn’t intended

   only for anyone who knows anything. Any other distribution, re-transmission, copying or disclosure of this message is highly encouraged. If you have received this transmission in error, just take a few deep breaths and relax, it’s really not a big deal. If you like it, pass it on, if you don’t like it, pass it on. Thanks! What the Swiftly Func? ALTCONF 2017 Presentation Created For Anyone Who Will Listen! Created By James Majors, iOS Developer http://bit.ly/AltConf2017

3. func iAm(_ who: Person?) -> Details { typealias Details =

   String guard let me = who else { return “Not Me!” } let whatIDo = “-> iOS Developer ” let atWhere = “@ POSSIBLE Mobile” return “\(me) \(whatIDo) \(atWhere)” } typealias Person = String let whoIAm: Person? = iAm(“James Majors”) // James Majors -> iOS Developer @ POSSIBLE Mobile

4. What the Swiftly Func? http://bit.ly/AltConf2017

5. Everything Old is New Again, for now… http://bit.ly/AltConf2017

6. What is Functional Programming*? (and how to use it in

   Swift) *FP from now on…

7. “A monad is a monoid in the category of endofunctors”

8. “A monad is a monoid in the category of endofunctors”

   http://james-iry.blogspot.com/2009/05/brief-incomplete-and-mostly-wrong.html

9. Functional Programming Topics • Airity • Partial Application • Idempotent

   • Functor • Lift • Referential Transparency • Lambda Calculus • Monoid • Monad • Applicative Functor • Semigroup • Setoid https://github.com/hemanth/functional-programming-jargon utm_source=hashnode.com

10. What’s Coming Up? • Simple Definition(s) • Differences between other

    Approaches • Explain what some of the terms mean • Example of a ‘Functional’ Drawing Engine http://bit.ly/AltConf2017
11. None

12. FP is just another TOOL in the tool box http://bit.ly/AltConf2017

13. None
14. None
15. None

16. • Side-Effect Free • Stateless • Immutable (the Data anyway)

    Functional Programming (FP) An approach that Strives to be… http://bit.ly/AltConf2017

17. Programming Paradigms http://bit.ly/AltConf2017

18. Programming Approaches http://bit.ly/AltConf2017

19. None

20. Object-Oriented Programming • Basic Building Block = Object (variables +

    functions) class SomeClass: NSObject { var aProperty: String func doSomething() { /* Transform ‘aProperty’ */ } } • Uses LOCAL variables (state) • Changing variables (mutable data) changes state • Side-Effects are usually how things get done class SomeClass: NSObject { var aProperty: String func doSomething() { /* Transform ‘aProperty’ */ } }

21. OK Side Effect Mutate Data Change State When you think

    of… A Button on a Screen Object
22. None

23. Functional Programming • Basic Building Block = Function (stateless) func

    function(value: Type) -> Type { let newValue = /* Transform ‘value’ */ return newValue } • Values (state) are passed INTO the Function • State is represented by immutable data • Side-Effects are don’t happen (Highly discouraged) func function(value: Type) -> Type { let newValue = /* Transform ‘value’ */ return newValue }

24. + 2 2 = 4 Side Effect Mutate Data Change

    State When you think of… Adding two numbers Function

25. What is a Function http://bit.ly/AltConf2017

26. Function Input Output ‘Pure’ Function

27. func squareANumber(x: Int) -> Int { return x * x

    } let squareANumber = { (x: Int) in x * x } Function: Closure Expression: Closure Expression

28. func squareANumber(x: Int) -> Int { return x * x

    } let squareANumber = { (x: Int) in x * x } Function: Closure Expression: Function Literal

29. Closure: Function with out a name a.k.a. Anonymous Function Function:

    Closure with a name

30. Closure Anonymous Function Block Inline Function Lambda Expression

31. Side-Effect Free http://bit.ly/AltConf2017

32. Functional Function Input Output ‘Pure’ Function

33. OOP Function Input

34. OOP Function Input OBJ

35. OOP Function Input OBJ OBJ OBJ OBJ OBJ OBJ OBJ

    OBJ

36. OOP Function Input Output OBJ OBJ OBJ OBJ OBJ OBJ

    OBJ OBJ

37. ‘add’ Function Input 4 Output (2, 2) func add(_ lhs:

    Int, _ rhs: Int) -> Int add(2, 2)

38. State or the lack thereof… http://bit.ly/AltConf2017

39. The value of ALL VARIABLES in an Object* at any

    instant in time http://bit.ly/AltConf2017

40. class ShapeClass { var shape: Shape var lineColor: Color var

    fillColor: Color } 3 Choices 3 Choices 3 Choices 27 POSSIBLE STATES

41. OBJ OBJ OBJ OBJ OBJ OBJ OBJ OBJ

42. Non-Mutable Data http://bit.ly/AltConf2017

43. Once a value is set, it CAN NOT be changed.

    http://bit.ly/AltConf2017

44. var value: Int = 10 value = 30 value =

    50

45. let value: Int = 10

46. Want to change it? http://bit.ly/AltConf2017

47. Want to change it? Make a new one… http://bit.ly/AltConf2017

48. let numbersArray: [Int] init(numbers: [Int]) { numbersArray = numbers }

    func add(number: Int) -> NumbersStruct { var newArray = Array(numbersArray) newArray.append(number) return NumbersStruct(numbers: newArray) } struct NumbersStruct { } }

49. Value Types not References Type http://bit.ly/AltConf2017

50. Value

51. Reference

52. Value: Swift Types enum struct class Array Dictionary Reference: func

53. • Side-Effect Free • Stateless • Uses Immutable Data Functional

    Programming (FP) More or less(ish) http://bit.ly/AltConf2017

54. Functions as ‘First-Class’ Type http://bit.ly/AltConf2017

55. func squareANumber(x: Int) -> Int { return x * x

    } let squareAnInt = { (x: Int) in x * x } let squareInt = squareAnInt Type: Closure Type: Closure let aNumber = 25

56. func squareANumber(x: Int) -> Int { return x * x

    } func doSomething(x: Int, function: ((Int) -> Int)) -> Int { -> Int { Type: Closure Type: func doubleANumber(x: Int) -> Int { return x + x } } return function(x) Type: Apply Function to ‘x’

57. func squareANumber(x: Int) -> Int { return x * x

    } func doSomething(x: Int, function: ((Int) -> Int)) -> Int { -> Int { func doubleANumber(x: Int) -> Int { return x + x } } return function(x) doSomething(x: 10, function: squareANumber) // 100

58. func squareANumber(x: Int) -> Int { return x * x

    } func doSomething(x: Int, function: ((Int) -> Int)) -> Int { -> Int { func doubleANumber(x: Int) -> Int { return x + x } } return function(x) doSomething(x: 10, function: squareANumber) // 100 doSomething(x: 10, function: doubleANumber) // 20

59. func doSomething(x: Int, function: ((Int) -> Int)) -> Int {

    Type: } return function(x) Type: Type: Closure

60. } x * x func doSomething(x: Int, function: ((Int) ->

    Int)) -> Int { Type: Closure Type: } return function(x) let doSomething(x: 10 { (x: Int) in ) , function: Type: Type: Closure return func squareANumber(x: Int) -> Int { return x * x } doSomething(x: 10, function: squareANumber)

61. } x * x func doSomething(x: Int, function: ((Int) ->

    Int)) -> Int { Type: } return function(x) let doSomething(x: 10 { (x: Int) in ) Type: Type: Closure return func squareANumber(x: Int) -> Int { return x * x } doSomething(x: 10, function: squareANumber)

62. } x * x func doSomething(x: Int, function: ((Int) ->

    Int)) -> Int { Type: } return function(x) let doSomething(x: 10 { (x: Int) in ) Type: Type: Closure func squareANumber(x: Int) -> Int { return x * x } doSomething(x: 10, function: squareANumber)

63. } x * x func doSomething(x: Int, function: ((Int) ->

    Int)) -> Int { Type: } return function(x) let doSomething(x: 10 // = 100 { (x: Int) in ) Type: Type: Closure Trailing Closure Syntax func squareANumber(x: Int) -> Int { return x * x } doSomething(x: 10, function: squareANumber)

64. func doWhat(x: Int) -> ((Int) -> Int) { Type: Closure

    Type: } doWhat

65. func squareANumber(x: Int) -> Int { return x * x

    } func doWhat(x: Int) -> ((Int) -> Int) { func doubleANumber(x: Int) -> Int { return x + x } } Inner Functions doWhat

66. func squareANumber(x: Int) -> Int { return x * x

    } func doWhat(x: Int) -> ((Int) -> Int) { func doubleANumber(x: Int) -> Int { return x + x } } if x % 2 == 0 { return squareANumber } else { return doubleANumber } doWhat squareANumber doubleANumber

67. func doWhat(x: Int) -> ((Int) -> Int) { } if

    x % 2 == 0 { return squareANumber } else { return doubleANumber } let squareANumber = { (x: Int) in x * x } let doubleANumber = { (x: Int) in x + x } doWhat { (x: Int) in x + x } { (x: Int) in x * x } squareANumber doubleANumber

68. squareIt(5) // = 25 func doWhat(x: Int) -> ((Int) ->

    Int) { } if x % 2 == 0 { return squareANumber } else { return doubleANumber } let squareIt = doWhat(x: 2) let doubleIt = doWhat(x: 3) doubleIt(5) // = 10 doWhat { (x: Int) in x + x } { (x: Int) in x * x }

69. Function take a Function as an argument Function return a

    Function Closure Closure http://bit.ly/AltConf2017

70. Higher-Order Functions http://bit.ly/AltConf2017

71. Higher-Order Functions Function that takes a Function as an argument

    Function that returns a Function Function that takes and returns a Function

72. IntFunc func takeFunction(x: Int, function: return function(x) } func returnFunction(x:

    Int) -> if x % 2 == 0 { return { (x: Int) in x + x } } else { return { (x: Int) in x * x } } } typealias IntFunc = (Int) -> Int ) -> Int { { ((Int) -> Int)

73. IntFunc func takeFunction(x: Int, function: return function(x) } func returnFunction(x:

    Int) -> if x % 2 == 0 { return { (x: Int) in x + x } } else { return { (x: Int) in x * x } } } typealias IntFunc = (Int) -> Int ) -> Int { { IntFunc

74. Map http://bit.ly/AltConf2017

75. Map func map<T, U>( function: (T) -> U) -> [U]

76. Map func map<T, U>( function: (T) -> U) -> [U]

    let new = [1,2,3,4,5].map { 10 * $0 }

77. Function [Array] [Results] { 10 * number } { 10

    * number } { 10 * number } { 10 * number } { 10 * } { 10 * } { 10 * } { 10 * } { 10 * } 1 2 3 4 5 [ , , , , ]

78. Function [Array] [Results] 10 { 10 * number } {

    10 * number } { 10 * number } { 10 * number } { 10 * } { 10 * } { 10 * } { 10 * } { 10 * } = 1 2 3 4 5 [ , , , , ]

79. Function [Array] [Results] 10 { 10 * } { 10

    * } { 10 * } { 10 * } { 10 * } = 20 = 30 = 40 = 50 = 1 2 3 4 5 [ , , , , ] 10 20 30 40 50

80. Map func map<T, U>( function: (T) -> U) -> [U]

    ‘Generic’ Types

81. Map func map<T, U>( function: (T) -> U) -> [U]

    let new = [1,2,3,4,5].map { 10 * $0 } Positional Argument (i.e. Function’s first Argument)

82. Map func map<T, U>( function: (T) -> U) -> [U]

    let new = [1,2,3,4,5].map { 10 * $0 } // new = [10,20,30,40,50]

83. Generic Types

84. func map<T, U>(function: (T) -> U) -> [U] Generic Types

85. func map<InputType, U>(function: (InputType) -> U) -> [U] Generic Types

86. func map<T, OutputType>(function: (T) -> OutputType) -> [OutputType] Generic Types

87. func map<InputType, OutputType>(function: (InputType) -> OutputType) -> [OutputType] Generic Types

88. func map<AType, BType>(function: (AType) -> BType) -> [BType] Generic Types

89. func map<Int, U>(function: (Int) -> U) -> [U] Generic Types

90. func map<Int, Int>(function: (Int) -> Int) -> [Int] Generic Types

91. func map<Int, String>(function: (Int) -> String) -> [String] Generic Types

92. func map<String, Int>(function: (String) -> Int) -> [Int] Generic Types

93. func map<T, U>(function: (T) -> U) -> [U] Generic Types

94. T = Some Type func map<T, U>(function: (T) -> U)

    -> [U] Int, Float, String, class, struct… Generic Types

95. T = Some Type U = Some Type func map<T,

    U>(function: (T) -> U) -> [U] Int, Float, String, class, struct… Int, Float, String, class, struct… Generic Types

96. Filter http://bit.ly/AltConf2017

97. Filter func filter<T>(function: (T) -> Bool) -> [T] let new

    = [1,2,3,4,5].filter { $0 % 2 == 0 }

98. Function [Array] [Results] { x % 2 == 0 }

    { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } 1 2 3 4 5 [ , ]

99. Function [Array] [Results] { x % 2 == 0 }

    { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } 2 3 4 5 [ , ] 1

100. Function [Array] [Results] false { x % 2 == 0

     } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } = 2 3 4 5 [ , ] 1

101. Function [Array] [Results] { x % 2 == 0 }

     { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } 2 3 4 5 [ , ]

102. Function [Array] [Results] { x % 2 == 0 }

     { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } 3 4 5 [ , ] 2

103. Function [Array] [Results] { x % 2 == 0 }

     { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } { x % 2 == 0 } true = 3 4 5 [ , ] 2

104. Function [Array] [Results] [ , ] 2 4 2 4

105. Filter

106. Filter func filter<T>(function: (T) -> Bool) -> [T]

107. Filter let new = [1,2,3,4,5].filter { $0 % 2 ==

     0 } func filter<T>(function: (T) -> Bool) -> [T]

108. Filter let new = [1,2,3,4,5].filter { $0 % 2 ==

     0 } // new = [2,4] func filter<T>(function: (T) -> Bool) -> [T]

109. Reduce http://bit.ly/AltConf2017

110. Reduce

111. Reduce func reduce<T>( initialValue: T, function: (T, T) -> T)

     -> T

112. { $0 + $1 } Reduce func reduce<T>( initialValue: T,

     function: (T, T) -> T) -> T let new = [1,2,3,4,5].reduce(0, + )

113. { $0 + $1 } Reduce func reduce<T>( initialValue: T,

     function: (T, T) -> T) -> T let new = [1,2,3,4,5].reduce(0, + ) Acc. Acc.

114. { $0 + $1 } Reduce func reduce<T>( initialValue: T,

     function: (T, T) -> T) -> T let new = [1,2,3,4,5].reduce(0, + ) [Element] Acc. [Element] Acc.

115. { $0 + $1 } Reduce func reduce<T>( initialValue: T,

     function: (T, T) -> T) -> T let new = [1,2,3,4,5].reduce(0, + )

116. Reduce func reduce<T>( initialValue: T, function: (T, T) -> T)

     -> T let new = [1,2,3,4,5].reduce(0, + )

117. Result [ , , , , ] 1 2 3

     4 5 Function [Array] Accumulator Initial Value + } { x acc Acc Init

118. Result [ , , , , ] 1 2 3

     4 5 Function [Array] + } { x acc Acc Init =

119. Result [ , , , , ] 1 2 3

     4 5 Function [Array] + } { x acc = 0 0

120. Result + } 1 2 3 4 5 Function [Array]

     { x acc + } { x acc 0

121. Result + } 1 2 3 4 5 Function [Array]

     { = 1 0

122. { $0 + $1 } Reduce func reduce<T>( initialValue: T,

     function: (T, T) -> T) -> T let new = [1,2,3,4,5].reduce(0, + ) [Element] Acc. [Element] Acc.

123. Reduce func reduce<T>( initialValue: T, function: (T, T) -> T)

     -> T let new = [1,2,3,4,5].reduce(0, + ) // new = 15

124. Imperative vs. Declarative ‘How To Do Something’ vs. ‘What You

     Want Done’ http://bit.ly/AltConf2017

125. Imperative Programming describes the algorithm http://bit.ly/AltConf2017

126. func arrayTimesTen(array: [Int]) -> [Int] { var outputArray = [Int]()

     for number in array { var newNumber = number * 10 outputArray.append(newNumber) } return outputArray } var outputArray = [Int]() for number in array { var newNumber = number * 10 outputArray.append(newNumber) } let newNumber = number * 10 outputArray.append(newNumber) return outputArray number * 10

127. func arrayTimesTen(array: [Int]) -> [Int] { var outputArray = [Int]()

     for number in array { var newNumber = number * 10 outputArray.append(newNumber) } return outputArray } var outputArray = [Int]() for number in array { var newNumber = number * 10 outputArray.append(newNumber) } let newNumber = number * 10 outputArray.append(newNumber) return outputArray number * 10

128. Declarative Programming describes the result http://bit.ly/AltConf2017

129. let mapped = array.map { $0 * 10 } let

     array = [1,2,3,4,5]

130. let mapped = array.map { $0 * 10 } let

     filtered = array.filter { $0 % 2 == 0 } let array = [1,2,3,4,5]

131. let mapped = array.map { $0 * 10 } let

     filtered = array.filter { $0 % 2 == 0 } let array = [1,2,3,4,5]

132. let mapped = array.map { $0 * 10 } let

     filtered = array.filter { $0 % 2 == 0 } let reduced = array.reduce(0, + ) let array = [1,2,3,4,5]

133. let mapped = array.map { $0 * 10 } let

     filtered = array.filter { $0 % 2 == 0 } let reduced = array.reduce(0, + ) let array = [1,2,3,4,5]

134. let mapIt = [1,2,3,4,5].map(timesTen) func timesTen(x: Int) -> Int {

     return x * 10 }

135. let mapIt = [1,2,3,4,5].map(timesTen) let filterIt = [1,2,3,4,5].filter(isEven) func timesTen(x:

     Int) -> Int { return x * 10 } func isEven(x: Int) -> Bool { return x % 2 == 0 }

136. let mapIt = [1,2,3,4,5].map(timesTen) let filterIt = [1,2,3,4,5].filter(isEven) func timesTen(x:

     Int) -> Int { return x * 10 } func isEven(x: Int) -> Bool { return x % 2 == 0 } let addIt = [1,2,3,4,5].reduce(0, add) func add(x: Int, y: Int) -> Int { return x + y }

137. Currying http://bit.ly/AltConf2017

138. ‘Partial Application’ of a Function http://bit.ly/AltConf2017

139. of a Function ‘Initialization’ http://bit.ly/AltConf2017

140. func addClosure(x: Int) -> ((Int) -> Int) { return {

     y in x * y } } let add = addClosure(x: 10) add(10) // 100 x x

141. func addClosure(x: Int) -> ((Int) -> Int) { return {

     y in x * y } } let add = addClosure(x: 10) add(100) // 1000 add(10) // 100 x x

142. ((col or: Color) -> DrawingItem) func itemWith(shape: Shape, color: Color)

     -> DrawingItem { return DrawingItem(shape: shape, color: color) } func someShape(shape: Shape) -> } (_ color: Color) -> DrawingItem { return { color in return itemWith(shape: shape, color: color) } shape color shape color { } let ovalShape = someShape(shape: .oval) let triangleShape = someShape(shape: .triangle) let blackOval = ovalShape(.black) let whiteTriangle = triangleShape(.white) return itemWith(shape: shape, color: color) itemWith

143. Functional Drawing Engine http://bit.ly/AltConf2017

144. Go forth and be Func’y! http://bit.ly/AltConf2017

145. This presentation doesn't contain any confidential information and isn’t intended

     only for anyone who knows anything. Any other distribution, re-transmission, copying or disclosure of this message is highly encouraged. If you have received this transmission in error, just take a few deep breaths and relax, it’s really not a big deal. If you like it, pass it on, if you don’t like it, pass it on. Thanks! What the Swiftly Func? ALTCONF 2017 Presentation Created For Anyone Who Will Listen! Created By James Majors, iOS Developer http://bit.ly/AltConf2016

146. Thanks! http://bit.ly/AltConf2017