scalania14.scala

  def grouped[T](ts : Seq[T], n: Int) = new Iterator[Seq[T]] {
    var cur : Seq[T] = ts
    def hasNext = !cur.isEmpty
    def next(): Seq[T] = {
      val (a, b) = cur.splitAt(n)
      cur = b
      a
    }
  }     

  def takeWhile[T](ts: Seq[T])(p: T => Boolean): Seq[T] = {
    @tailrec
    def go(ts: Seq[T], acc: Seq[T]): Seq[T] = ts match {
      case e :: es if p(e) => go(es, e +: acc)
      case _ => acc.reverse
    }
    go(ts, Seq())
  }