Is there sequential Future.find?

Question

I have some side-effectful function,

def f(): Future[Int] = {
  val n = Random.nextInt()
  println(s\"Generated $n\")
  Future(n)
}

and I

Answer 1

First, let's make the futures we aren't interested in fail:

val s1 = s.map(_.filter(success))

Now you can combine two such futures and get the first successful value using fallbackTo. And just fold the stream, starting with a known-bad future:

def firstSuccess[T](stream: Stream[Future[T]]): Future[T] = 
  if (stream.isEmpty)
    Future.failed(new NoSuchElementException)
  else
    stream.head.fallbackTo(firstSuccess(stream.tail))