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ported to Swift 3 #2

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69 changes: 42 additions & 27 deletions Functors-Applicatives-Monads-In-Pictures.playground/Contents.swift
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Original file line number Diff line number Diff line change
@@ -1,3 +1,6 @@



//: This is a companion Playground for the article "Swift Functors, Applicatives, and Monads in Pictures", available at http://www.mokacoding.com/blog/functor-applicative-monads-in-pictures/
//: The article itself is a translation of the original "Functors, Applicatives, and Monads in Pictures" written for Haskell by Aditya Bhargava, available at http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html
//:
Expand All @@ -18,42 +21,43 @@ func plusThree(addend: Int) -> Int {
return addend + 3
}

Optional.Some(2).map(plusThree)
Optional.some(2).map(plusThree)

//: We can use autoclosures and be more succint

Optional.Some(2).map { $0 + 3 }
Optional.some(2).map { $0 + 3 }

//: If the optional value is .None, map will return .None (nil)

Optional.None.map { $0 + 3 }
Optional.none.map { $0 + 3 }

//: Map implementation might look like this

func myMap<T, U>(a: T?, f: T -> U) -> U? {
func myMap<T, U>(a: T?, f: (T) -> U) -> U? {
switch a {
case .Some(let x): return f(x)
case .None: return .None
case .some(let x): return f(x)
case .none: return .none
}
}

myMap(Optional.Some(2), f: { $0 + 3 })
myMap(a: Optional.some(2), f: { $0 + 3 })

//: We can define an infix operator

infix operator <^> { associativity left }
infix operator <^>: MultiplicationPrecedence

func <^><T, U>(f: T -> U, a: T?) -> U? {
func <^><T, U>(f: (T) -> U, a: T?) -> U? {
return a.map(f)
}

plusThree <^> Optional.Some(2)
plusThree <^> Optional.some(2)

//: Turns out functions can be mapped as well. Functions are functors too!

typealias IntFunction = Int -> Int
typealias IntFunction = (Int) -> Int

func map(f: IntFunction, _ g: IntFunction) -> IntFunction {
func map(_
f: @escaping IntFunction, _ g: @escaping IntFunction) -> IntFunction {
return { x in f(g(x)) }
}

Expand All @@ -62,16 +66,17 @@ foo(10)

//: ## Applicative
extension Optional {
func apply<U>(f: (Wrapped -> U)?) -> U? {
func apply<U>(_ f: ((Wrapped) -> U)?) -> U? {
switch f {
case .Some(let someF): return self.map(someF)
case .None: return .None
case .some(let someF): return self.map(someF)
case .none: return .none
}
}
}

extension Array {
func apply<U>(fs: [Element -> U]) -> [U] {
func apply<U>(_
fs: [(Element) -> U]) -> [U] {
var result = [U]()
for f in fs {
for element in self.map(f) {
Expand All @@ -82,50 +87,60 @@ extension Array {
}
}

infix operator <*> { associativity left }
infix operator <*>: MultiplicationPrecedence

func <*><T, U>(f: (T -> U)?, a: T?) -> U? {
func <*><T, U>(f: ((T) -> U)?, a: T?) -> U? {
return a.apply(f)
}

func <*><T, U>(f: [T -> U], a: [T]) -> [U] {
func <*><T, U>(f: [(T) -> U], a: [T]) -> [U] {
return a.apply(f)
}

Optional.Some({ $0 + 3 }) <*> Optional.Some(2)
Optional.some({ $0 + 3 }) <*> Optional.some(2)

let arrayApplicative = [ { $0 + 3 }, { $0 * 2 } ] <*> [1, 2, 3]
//: _Playground (as of Xcode 7 Beta 3) doesn't seem to be happy show the result of array applications , so we'll print open the console with Cmd + Y to see it_

print(arrayApplicative)

func curriedAddition(a: Int)(b: Int) -> Int {
public func curry<A, B, C>(_ function: @escaping (A, B) -> C) -> (A) -> (B) -> C {
return { (a: A) -> (B) -> C in { (b: B) -> C in function(a, b) } }
}

func addition(a: Int, b: Int) -> Int {
return a + b
}

let curriedAddition = curry(addition)

curriedAddition(2)(3)

curriedAddition <^> Optional(2) <*> Optional(3)

func curriedTimes(a: Int)(b: Int) -> Int {
return a * b
func multiplication(a: Int, b: Int) -> Int {
return a * b
}

let curriedTimes = curry(multiplication)

curriedTimes <^> Optional(5) <*> Optional(3)

//: ## Monads

infix operator >>- { associativity left }
infix operator >>- : MultiplicationPrecedence

func >>-<T, U>(a: T?, f: T -> U?) -> U? {
func >>-<T, U>(a: T?, f: (T) -> U?) -> U? {
return a.flatMap(f)
}

func half(a: Int) -> Int? {
return a % 2 == 0 ? a / 2 : .None
return a % 2 == 0 ? a / 2 : .none
}

Optional(3) >>- half
Optional(4) >>- half
Optional.None >>- half
Optional.none >>- half

//: We can even chain >>-

Expand Down
2 changes: 1 addition & 1 deletion Functors-Applicatives-Monads-In-Pictures.playground/contents.xcplayground
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@@ -1,4 +1,4 @@
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<playground version='5.0' target-platform='ios' requires-full-environment='true'>
<playground version='5.0' target-platform='ios' display-mode='rendered'>
<timeline fileName='timeline.xctimeline'/>
</playground>
Empty file modified ...pplicatives-Monads-In-Pictures.playground/playground.xcworkspace/contents.xcworkspacedata
100644 → 100755
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28 changes: 14 additions & 14 deletions Functors-Applicatives-Monads-In-Pictures.playground/timeline.xctimeline
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Expand Up @@ -3,72 +3,72 @@
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Expand Down
Empty file modified README.md
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