scala qsort

def qsort[T <% Ordered[T]](list : List[T] ) : List[T] =
  {
    if ( list.isEmpty )
      list
    else if ( list.size == 1 )
      List[T](list(0))
    else
    {
      val first = list(0)
      val tail = list.tail
      val left = tail.filter( { (x : T) =>  x < first }  )
      val right = tail.filter( { (x : T) =>  x >= first } )
      qsort(left) ++ List[T](first) ++ qsort(right)
    }
  }