if else for

gistfile1.scala

  case class Message(username: String, content: String)
  val list = List(Message("aaa", "111"), Message("aaa", "222"),
    Message("bbb", "333"), Message("aaa", "444"))

  if (list.isEmpty) Nil
  else
    list.head :: (
      for (List(m1, m2) <- list.sliding(2))
        yield if (m1.username == m2.username)
        m2.copy(username = "") else m2).toList