What you describe is fundamentally impossible: if you need to process all elements in order to know the processing rule to be applied to those elements then you’ll have to store the elements—how else could it work?
The buffering solution you show is a good one, thanks for sharing! Regards, Roland On Wed, Aug 12, 2015 at 8:58 AM, wwagner4 <[email protected]> wrote: > I cannot find a solution for accessing the elements of a stream more than > ones inside a flow without buffering the complete stream. To illustrate the > problem I created the following example: > > def randomIntegersSource(size: Int): Source[Int, _] = { > val iter = > Iterator.continually(ThreadLocalRandom.current().nextInt(100)) > Source(() => iter.take(size)) > } > > test("normalize a stream of integers") { > implicit val sys = ActorSystem("sys") > try { > implicit val materializer = ActorMaterializer() > > val src: Source[Int, _] = randomIntegersSource(size = 20) > > // Converts a stream of positive integers to doubles ranging from > 0 to 1. > // The gratest input value converts to 1 > val normalizeFlow: Flow[Int, Double, _] = ??? > > val f = src.via(normalizeFlow).runForeach {norm => println("%.3f" > format norm)} > > Await.result(f, 2.second) > } finally { > sys.shutdown() > } > } > > > Inside the 'normalizeFlow' I have to process the stream twice. First to > find the maximum value and second to calculate the normalized values. > > Does anyone know an implementation for 'normalizeFlow' that runs with > arbritrary sized streams and that does not need to buffer the whole stream > in order to work? > > Here normalize.scala > <https://github.com/wwagner4/akka-streams-tryout/blob/master/src/test/scala/normalize.scala> > you can find the complete example with a buffering solution. > > -- > >>>>>>>>>> Read the docs: http://akka.io/docs/ > >>>>>>>>>> Check the FAQ: > http://doc.akka.io/docs/akka/current/additional/faq.html > >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user > --- > You received this message because you are subscribed to the Google Groups > "Akka User List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > -- Akka Team Typesafe - Reactive apps on the JVM Blog: letitcrash.com Twitter: @akkateam -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.
