Apply a reduction function on the incoming elements and pass the result to the next invocation.
def reduce[T](f: (T, T) => T): Sink[T, Future[T]]
Apply a reduction function on the incoming elements and pass the result to the next invocation. The first invocation receives the two first elements of the flow.
Materializes into a
CompletionStage that will be completed by the last result of the reduction function.
backpressures when the previous reduction function invocation has not yet completed
val source = Source(1 to 10)
val result = source.runWith(Sink.reduce[Int]((a, b) => a + b))
Source<Integer, NotUsed> ints = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
CompletionStage<Integer> sum = ints.runWith(Sink.reduce((a, b) -> a + b), materializer);
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