LazySplitEvery.Swift

extension Array {
  func splitEvery(nInEach: Int)
    -> LazySequence<MapSequenceView<StrideTo<Int>, ArraySlice<T>>> {
      return lazy(stride(from: 0, to: self.count, by: nInEach)).map {
        from in self[from ..< advance(from, nInEach, self.count)]
      }
  }
}