scala> 1 +: List(2, 3) res0: List[Int] = List(1, 2, 3) scala> 1 +: 2 +: List(2, 3) res1: List[Int] = List(1, 2, 2, 3) scala> 1 :: 2 :: List(2, 3) res2: List[Int] = List(1, 2, 2, 3) scala> "hoge" ++ List("fuga", "bar") res3: scala.collectio…