Simple example of Cats OptionT monad transformer usage vs plain Scala

MonadT.scala

  import cats.data._
  import cats.implicits._

  val li=List(Option(1),Option(2), None)

  println(OptionT(li).map(_+10).value)
//List(Some(11), Some(12), None)

  println(li.map(_.map(_+10)))
//List(Some(11), Some(12), None)

  println(OptionT(li).foldLeft(0)(_+_))
//3

  println(li.foldLeft(0){_+_.getOrElse(0)})
//3