Monad.scala

trait Function {
  def name: String
}

case class ShellFunction(name: String) extends Function
case class ScalaFunction(name: String) extends Function
val l: List[Option[Function]] = List(None, Some(ShellFunction("build")), None)

val resultUsingForConstruct = for (
  i <- l;
  j <- i
) yield (Some(ScalaFunction(j.name)))

val resultUsingFlatMap = l flatMap {
  i: Option[Function] => i map {
    j: Function => Some(ScalaFunction(j.name))
  }
}

Output from both the constructs: 
Result using for construct: List(Some(ScalaFunction(build)))
Result using flatmap construct: List(Some(ScalaFunction(build)))