You need to have the '++' on the previous line, or else it doesn't compile.

```scala
scala> def x() = { 
     |   List(1,2,3,4) ++
     |   List(7,8,9,0)
     | }
x: ()List[Int]

scala> def y() = {
     |   List(1,2,3,4)
     |   ++ List(7,8,9,0)
     | }
<console>:9: error: not found: value ++
         ++ List(7,8,9,0)
         ^
```