MergeSorting.scala

def sort(src: List[Int]): List[Int] = src match {
  case (Nil|_::Nil) => src
  case _ =>
    def merge(l: List[Int], r: List[Int]): List[Int] = (l, r) match {
      case (Nil, ys) => ys
      case (xs, Nil) => xs
      case (x::xs, y::ys) => if(x < y) x::merge(xs, r) else y::merge(l, ys)
    }
    val (l, r) = src.splitAt(src.length / 2)
    merge(sort(l), sort(r))
}
val list = List(8,4,3,7,6,5,2,1)
println(sort(list))