Added playground

0004-adt/Algebraic Data Types.playground/Contents.swift

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+
+struct Pair<A, B> {
+  let first: A
+  let second: B
+}
+
+Pair<Bool, Bool>.init(first: true, second: true)
+Pair<Bool, Bool>.init(first: true, second: false)
+Pair<Bool, Bool>.init(first: false, second: true)
+Pair<Bool, Bool>.init(first: false, second: false)
+
+enum Three {
+  case one
+  case two
+  case three
+}
+
+Pair<Bool, Three>.init(first: true, second: .one)
+Pair<Bool, Three>.init(first: true, second: .two)
+Pair<Bool, Three>.init(first: true, second: .three)
+Pair<Bool, Three>.init(first: false, second: .one)
+Pair<Bool, Three>.init(first: false, second: .two)
+Pair<Bool, Three>.init(first: false, second: .three)
+
+let _: Void = Void()
+let _: Void = ()
+let _: () = ()
+
+func foo(_ x: Int) /* -> Void */ {
+  // return ()
+}
+
+Pair<Bool, Void>.init(first: true, second: ())
+Pair<Bool, Void>.init(first: false, second: ())
+
+Pair<Void, Void>.init(first: (), second: ())
+
+enum Never {}
+
+//let _: Never = ???
+
+//Pair<Bool, Never>.init(first: true, second: ???)
+
+
+// Pair<Bool, Bool>  = 4 = 2 * 2
+// Pair<Bool, Three> = 6 = 2 * 3
+// Pair<Bool, Void>  = 2 = 2 * 1
+// Pair<Void, Void>  = 1 = 1 * 1
+// Pair<Bool, Never> = 0 = 2 * 0
+
+
+enum Theme {
+  case light
+  case dark
+}
+
+enum State {
+  case highlighted
+  case normal
+  case selected
+}
+
+struct Component {
+  let enabled: Bool
+  let state: State
+  let theme: Theme
+}
+
+// 2 * 3 * 2 = 12
+
+// Pair<A, B> = A * B
+// Pair<Bool, Bool> = Bool * Bool
+// Pair<Bool, Three> = Bool * Three
+// Pair<Bool, Void> = Bool * Void
+// Pair<Bool, Never> = Bool * Never
+
+// Pair<Bool, String> = Bool * String
+// String * [Int]
+// [String] * [[Int]]
+// Never = 0
+// Void = 1
+// Bool = 2
+// 2 * String
+
+enum Either<A, B> {
+  case left(A)
+  case right(B)
+}
+
+Either<Bool, Bool>.left(true)
+Either<Bool, Bool>.left(false)
+Either<Bool, Bool>.right(true)
+Either<Bool, Bool>.right(false)
+// Either<Bool, Bool> = 4 = 2 + 2
+// 2 + 2
+
+Either<Bool, Three>.left(true)
+Either<Bool, Three>.left(false)
+Either<Bool, Three>.right(.one)
+Either<Bool, Three>.right(.two)
+Either<Bool, Three>.right(.three)
+// Either<Bool, Three> = 5 = 2 + 3
+// Bool + Three
+// 2 + Three
+
+Either<Bool, Void>.left(true)
+Either<Bool, Void>.left(false)
+Either<Bool, Void>.right(())
+// Either<Bool, Void> = 3 = 2 + 1
+// 2 + 1
+
+Either<Bool, Never>.left(true)
+Either<Bool, Never>.left(false)
+//Either<Bool, Never>.right(???)
+// Either<Bool, Never> = 2 = 2 + 0
+// 2 + 0
+
+struct Unit {}
+// enum Never {}
+
+let unit = Unit()
+
+extension Unit: Equatable {
+  static func == (lhs: Unit, rhs: Unit) -> Bool {
+    return true
+  }
+}
+
+//extension Void {}
+
+
+
+func sum(_ xs: [Int]) -> Int {
+  var result: Int = 0
+  for x in xs {
+    result += x
+  }
+  return result
+}
+
+func product(_ xs: [Int]) -> Int {
+  var result: Int = 1
+  for x in xs {
+    result *= x
+  }
+  return result
+}
+
+let xs = [Int]()
+sum(xs)
+product(xs)
+
+sum([1, 2]) + 0 == sum([1, 2])
+product([1, 2]) * 1 == product([1, 2])
+
+// Void = 1
+// A * 1 = A = 1 * A
+
+// Never = 0
+// A * 0 = 0 = 0 * A
+
+// A + 0 = A = 0 + A
+
+// A + 1 = 1 + A = A?
+
+//Either<A, Void>
+
+//Either<Pair<A, B>, Pair<A, C>>
+
+// A * B + A * C = A * (B + C)
+
+//Pair<A, Either<B, C>>
+
+
+// Pair<Either<A, B>, Either<A, C>>
+
+// (A + B) * (A + C)
+// A * A + A * C + B * A + B * C
+
+import Foundation
+
+//URLSession.shared
+//  .dataTask(with: <#T##URL#>, completionHandler: <#T##(Data?, URLResponse?, Error?) -> Void#>)
+
+// (Data + 1) * (URLResponse + 1) * (Error + 1)
+//   = Data * URLResponse * Error
+//     + Data * URLResponse
+//     + URLResponse * Error
+//     + Data * Error
+//     + Data
+//     + URLResponse
+//     + Error
+//     + 1
+
+// Data * URLResponse + Error
+
+//Either<Pair<Data, URLResponse>, Error>
+//Result<(Data, URLResponse), Error>
+//Result<Date, Never>
+//Result<A, Error>?

0004-adt/Algebraic Data Types.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>