scalania12.scala

  def pack[T](ts: Seq[T]): Seq[Seq[T]] = {
    @tailrec
    def go(ts: Seq[T], acc: Seq[Seq[T]]): Seq[Seq[T]] = ts match {
      case Seq() => acc
      case head +: tail =>
        val (same, different) = ts.span(_ == head) // ts.partition(_ == head)
        go(different, acc :+ same)
    }
    go(ts, Seq()) // Seq(Seq())
  }

  def flatten(ls: Seq[Any]): Seq[Any] = ls.flatMap {
    case l: Seq[_] => flatten(l)
    case e => Seq(e)
  }