grouped.scala

  def grouped[T](ts: Seq[T], n: Int) = {
    def go(xs: Seq[T], acc: Seq[Seq[T]]): Seq[Seq[T]] = xs match {
      case Nil => acc
      case _ =>
        val (first, second) = xs.splitAt(n)
        go(second, first +: acc)
    }
    go(ts, Seq()).reverse
  }