Do you remember themap, from few SKBs ago ?
As a reminder,mapallows you to transform aList[A]into aList[B].
What will happen ifBis aListas well ?
flattenallows you to turn aList[List[A]]into aList[A].
Try to experiment with othercontainerssuch asOptionwe saw in the past.
What happen if you do
val a: Option[Int] = Some(12)
val aa: Option[Option[Int]] = a.map(x => Some(x))
val flattenA: Option[Int] = aa.flatten
Reveal more information and clues