05.Answer

extension [R](self: Pull[Int, R])
  def slidingMean(n: Int): Pull[Double, R] =
    def go(
      window: collection.immutable.Queue[Int],
      p: Pull[Int, R]
    ): Pull[Double, R] =
      p.uncons.flatMap:
        case Left(r) => Result(r)
        case Right((hd, tl)) =>
          val newWindow = if window.size < n then window :+ hd
                                             else window.tail :+ hd
          val meanOfNewWindow = newWindow.sum / newWindow.size.toDouble
          Output(meanOfNewWindow) >> go(newWindow, tl)
    go(collection.immutable.Queue.empty, self)