do-until.swift

// The DoUntil struct holds the action that is
// the loop body
struct DoUntil {
  let action: () -> ()

  init(action: () -> ()) {
    self.action = action
  }
  
  // Using a method like this allows replacing what would have
  // been a space in 
  // do {
  //    println("i = \(i)")
  //    i++
  // } until (i == 10)
  // with a dot instead
  func until(condition: @autoclosure () -> BooleanType) {
    while condition().boolValue == false {
      action()
    }
  }
}

func Do(block: () -> ()) -> DoUntil {
  return DoUntil(action: block)
}

i = 0

Do {
  println("i = \(i)")
  i++
}.until(i == 10)

i