SebastianAas

for {
    a1 <- Future(Set(1, 2, 3))
    b1 <- Future(Set(1, 2, 3))
} yield {
    for {
        x <- a1
        y <- b1 if y > 2
    } yield {
        x + y
    }

SebastianAas

def example() = {
    val a1 = Set(1, 2, 3)
    val b2 = Set(1, 2, 3)
    for {
        x <- a1
        y <- b2 if y > 2
    } yield {
        x + y
    }
}

SebastianAas

def example() = {
    val a1 = Set(1, 2, 3)
    val b2 = Set(1, 2, 3)
    a1
    .flatMap(x =>
        b2
        .withFilter(y => y > 2)
        .map(y => x + y)
    )
}

SebastianAas

final case class SetF[A](_future: Future[Iterable[A]]) extends AnyVal {
    def future: Future[Set[A]] = _future.map(_.toSet)
    def flatMap[B](f: A => SetF[B]): SetF[B] = {
        val newFuture: Future[Set[B]] = for {
          list: Set[A]        <- future
          result: Set[Set[B]] <- Future.sequence(list.map(f(_).future))
        } yield {
          result.flatten
        }
        SetF(newFuture)

SebastianAas

def addAllCombinations() = {
    val a = Future(Set(1, 2, 3))
    val b = Future(Set(1, 2, 3))
    for {
        x <- SetF(a)
        y <- SetF(b) if y > 2
    } yield {
        x + y
    }
} // Result: Future[Set(4,5,6)]

SebastianAas

object SetF {
def lift[A](f: Future[A]): SetF[A] = SetF(f.map(Set(_)))
def apply[A](o: Iterable[A]): SetF[A] = 
    SetF(Future.successful(o match {
      case o: Set[_] => o.asInstanceOf[Set[A]]
      case o         => o.toSet
      }))
}

SebastianAas

def example2() = {
    val a = Future(0.5)
    val b = Future(Set(1, 2, 3))
    for {
        x <- SetF.lift(a)
        y <- SetF(b)
    } yield {
        x * y
    }
}