mergestream.scala

object Util {
  /** Merges a collection of streams into a single stream.
    *
    * Returns a sorted stream if all input streams are sorted.
    */
  def mergeStreams[A](streams: Traversable[Stream[A]])(implicit ord: Ordering[A]): Stream[A] = {
    val streams1 = streams.toList filterNot (_.isEmpty) sortBy (_.head)
    if (streams1.isEmpty)
      Stream.empty
    else {
      val first = streams1.head
      first.head #:: mergeStreams(first.tail :: streams1.tail)
    }
  }
  
  /** Merges several streams into a single stream.
    *
    * Returns a sorted stream if all input streams are sorted.
    */
  def mergeStreams[A](streams: Stream[A]*)(implicit ord: Ordering[A]): Stream[A] =
    mergeStreams(streams)
}