ListMonadSwap.sc

import cats.Monad

import scala.concurrent.Future
import scala.language.higherKinds

import scala.concurrent.ExecutionContext.Implicits.global

object Swap {

  def apply[F[_], A](l: List[F[A]])(implicit m: Monad[F]): F[List[A]] =
    l.foldLeft(m pure List.empty[A])((futureList, futureNext) =>
      m.flatMap(futureList)(list => m.map(futureNext)(_ :: list))
    )

  def apply[A](l: List[Future[A]]): Future[List[A]] =
    l.foldLeft(Future successful List.empty[A])((futureList, futureNext) =>
      futureList flatMap (list => futureNext map (_ :: list))
    )

}

Swap(List(Future successful 1, Future successful 2))