IT Monkey Life

class A {
  var aProperty: [Int]
  func doSomething() { ... }
  dynamic doSomethingElse() { ... }
}

class B : A {
  override var aProperty {
    get { ... }
    set { ... }
  }

  override func doSomething() { ... }
}

func usingAnA(a: A) {
  a.doSomething()
  a.aProperty = ...
}

final class C {
  // No declarations in class 'C' can be overridden.
  var array1: [Int]
  func doSomething() { ... }
}

class D {
  final var array1 [Int] // 'array1' cannot be overridden by a computed property.
  var array2: [Int]      // 'array2' *can* be overridden by a computed property.
}

func usingC(c: C) {
   c.array1[i] = ... // Can directly access C.array without going through dynamic dispatch.
   c.doSomething() = ... // Can directly call C.doSomething without going through virtual dispatch.
}

func usingD(d: D) {
   d.array1[i] = ... // Can directly access D.array1 without going through dynamic dispatch.
   d.array2[i] = ... // Will access D.array2 through dynamic dispatch.
}

private class E {
  func doSomething() { ... }
}

class F {
  private var myPrivateVar : Int
}

func usingE(e: E) {
  e.doSomething() // There is no sub class in the file that declares this class.
                  // The compiler can remove virtual calls to doSomething()
                  // and directly call A’s doSomething method.
}

func usingF(f: F) -> Int {
  return f.myPrivateVar
}

// Don't use a class here.
struct PhonebookEntry {
  var name : String
  var number : [Int]
}

var a : [PhonebookEntry]

class C { ... }
var a: ContiguousArray<C> = [C(...), C(...), ..., C(...)]

var c: [Int] = [ ... ]
var d = c        // No copy will occur here.
d.append(2)      // A copy *does* occur here.

func append_one(a: [Int]) -> [Int] {
  a.append(1)
  return a
}

var a = [1, 2, 3]
a = append_one(a)

func append_one_in_place(inout a: [Int]) {
  a.append(1)
}

var a = [1, 2, 3]
append_one_in_place(&a)

a : [Int]
b : [Int]
c : [Int]

// Precondition: for all a[i], b[i]: a[i] + b[i] does not overflow!
for i in 0 ... n {
  c[i] = a[i] &+ b[i]
}

class MySwiftFunc<T> { ... }

MySwiftFunc<Int> X    // Will emit code that works with Int...
MySwiftFunc<String> Y // ... as well as String.

class MyStack<T> {
  func push(element: T) { ... }
  func pop() -> T { ... }
}

func myAlgorithm(a: [T], length: Int) { ... }

// The compiler can specialize code of MyStack[Int]
var stackOfInts: MyStack[Int]
// Use stack of ints.
for i in ... {
  stack.push(...)
  stack.pop(...)
}

var arrayOfInts: [Int]
// The compiler can emit a specialized version of 'myAlgorithm' targeted for
// [Int]' types.
myAlgorithm(arrayOfInts, arrayOfInts.length)

//Framework.swift:

protocol Pingable { func ping() -> Self }
protocol Playable { func play() }

extension Int : Pingable {
  func ping() -> Int { return self + 1 }
}

class Game<T : Pingable> : Playable {
  var t : T

  init (_ v : T) {t = v}

  func play() {
    for _ in 0...100_000_000 { t = t.ping() }
  }
}

func play_a_game(game : Playable ) {
  // This check allows the optimizer to specialize the
  // generic call 'play'
  if let z = game as? Game<Int> {
    z.play()
  } else {
    game.play()
  }
}

/// -------------- >8

// Application.swift:

play_a_game(Game(10))

protocol P {}
struct Node : P {
  var left, right : P?
}

struct Tree {
  var node : P?
  init() { ... }
}

struct tree : P {
  var node : [P?]
  init() {
    node = [ thing ]
  }
}

final class Ref<T> {
  var val : T
  init(_ v : T) {val = v}
}

struct Box<T> {
    var ref : Ref<T>
    init(_ x : T) { ref = Ref(x) }

    var value: T {
        get { return ref.val }
        set {
          if (!isUniquelyReferencedNonObjC(&ref)) {
            ref = Ref(newValue)
            return
          }
          ref.val = newValue
        }
    }
}

final class Node {
 var next: Node?
 var data: Int
 ...
}

var Ref : Unmanaged<Node> = Unmanaged.passUnretained(Head)

while let Next = Ref.takeUnretainedValue().next {
  ...
  Ref = Unmanaged.passUnretained(Next)
}

protocol Pingable : class { func ping() -> Int }