flatten.scala

// "x => x + 1" could be reduced to "_ + 1" using placeholder syntax.
> Some(10) flatMap(x => x + 1)
res0: Option[Int] = Some(45)

> Some(10) flatMap(x => None)
res0: Option[Nothing] = None

> List(Some(1), None, Some(3), None).map(a => \
  a.flatMap(b => Some(b + 1)))
res0: List[Option[Int]] = List(Some(2), None, Some(4), None)

// if you want to get the list of Ints
> List(Some(1), None, Some(3), None).map(a => \
     a.flatMap(b => Some(b + 1)))
         flatten