p07.scala

def flatten(lst: List[Any]): List[Any] = {
  lst match {
    case Nil => List[Any]()
    case (head:List[Any]) :: body => flatten(head) ::: flatten(body)
    case head :: body => head :: flatten(body)
  }
}

flatten(List(List(1, 1), 2, List(3, List(5, 8))))