flatmap_example.scala

//list of integers
val myList: List[Int] = List(1, 2, 7, 3)

//function to give neighbouring integers of an integer
def neighbourFunc: Int => List[Int] = value => List(value - 1, value + 1)

//using map() will give us an unflattened list
myList.map(neighbourFunc)         //output: List(List(0, 2), List(1, 3), List(6, 8), List(2, 4))

//using map() + flatten() will give us a flattened list
myList.map(neighbourFunc).flatten //output: List(0, 2, 1, 3, 6, 8, 2, 4)

//using flatMap() will give us a flattened list
myList.flatMap(neighbourFunc)     //output: List(0, 2, 1, 3, 6, 8, 2, 4)