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Don't use scala Future
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| trait TimedExecution { | |
| implicit val materializer: Materializer | |
| def delayed[A, B](f: A => B)(delay: FiniteDuration): A => Future[B] = a => Source.tick(delay, delay, a).take(1).map(f).runWith(Sink.head) | |
| def delayedValue[A](a: => A)(delay: FiniteDuration): Future[A] = delayed[Unit, A](_ => a)(delay)(()) | |
| } | |
| /** | |
| * Utility functions to delay function executions or values. It needs a `Materializer` implicitly available | |
| * | |
| * Usage: | |
| * ``` | |
| * val te = TimedExecution() | |
| * import te._ | |
| * | |
| * delayed[Int, Int](_ + 1)(5.seconds) | |
| * ``` | |
| */ | |
| object TimedExecution { | |
| def apply()(implicit mat: Materializer): TimedExecution = new TimedExecution { | |
| override implicit val materializer: Materializer = mat | |
| } | |
| } | |
| object TestTraverse extends App { | |
| import cats.implicits._ | |
| implicit val actorSystem = ActorSystem() | |
| implicit val materializer = ActorMaterializer() | |
| import actorSystem.dispatcher | |
| val te = TimedExecution() | |
| import te._ | |
| def attempt1: Unit = { | |
| val start = System.nanoTime() | |
| println(s"starting at $start") | |
| val xs: Future[List[Int]] = List(1, 2, 3, 4).traverse(i => delayedValue(i)(i.seconds)) | |
| println("result: " + Await.result(xs, 30.seconds)) | |
| val end = System.nanoTime() | |
| println(s"ended at $end") | |
| println(s"it took ${(end - start) / 1000000} ms") | |
| } | |
| def attempt2: Unit = { | |
| val start = System.nanoTime() | |
| println(s"starting at $start") | |
| val xs: Future[List[Int]] = List(1, 2, 3, 4).foldLeft(Future(List[Int]()))((f, i) => f.flatMap(xs => delayedValue(i)(i.seconds).map(_ :: xs))) | |
| println("result: " + Await.result(xs, 30.seconds)) | |
| val end = System.nanoTime() | |
| println(s"ended at $end") | |
| println(s"it took ${(end - start) / 1000000} ms") | |
| } | |
| attempt1 | |
| println("### ATTEMPT WITH FOLDLEFT ###") | |
| attempt2 | |
| } | |
| object TestTraverseCatsEffect extends IOApp { | |
| import cats.implicits._ | |
| def f(i: Int): IO[Int] = IO.sleep(i.seconds) *> IO.delay(i) | |
| val prg: IO[Unit] = for { | |
| start <- IO.delay(System.nanoTime()) | |
| _ <- IO.delay(println(s"starting at $start")) | |
| res <- List(1, 2, 3, 4).traverse(f) | |
| _ <- IO.delay(println(s"result: $res")) | |
| end <- IO.delay(System.nanoTime()) | |
| _ <- IO.delay(println(s"it took ${(end - start) / 1000000} ms")) | |
| } yield () | |
| override def run(args: List[String]): IO[ExitCode] = prg *> IO.delay(ExitCode.Success) | |
| } | |
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