multiFlatMaps.swift

func map<T, U, V>(vals: (T?, U?), transform: (T, U) -> V) -> V? {
  if let x = vals.0, y = vals.1 {
    return transform(x, y)
  } else {
    return nil
  }
}

func map<T, U, V>(val0: T?, _ val1: U?, transform: (T, U) -> V) -> V? {
  if let x = val0, y = val1 {
    return transform(x, y)
  } else {
    return nil
  }
}

func flatMap<T, U, V>(vals: (T?, U?), transform: (T, U) -> V?) -> V? {
  if let x = vals.0, y = vals.1 {
    return transform(x, y)
  } else {
    return nil
  }
}

func flatMap<T, U, V>(val0: T?, _ val1: U?, transform: (T, U) -> V?) -> V? {
  if let x = val0, y = val1 {
    return transform(x, y)
  } else {
    return nil
  }
}