Transform each element into zero or more elements that are individually passed downstream.
Transform each element into zero or more elements that are individually passed downstream. This can be used to flatten collections into individual stream elements. Returning an empty iterable results in zero elements being passed downstream rather than the stream being cancelled.
See also statefulMapConcat
The following takes a stream of integers and emits each element twice downstream.
emits when the mapping function returns an element or there are still remaining elements from the previously calculated collection
backpressures when downstream backpressures or there are still available elements from the previously calculated collection
completes when upstream completes and all remaining elements has been emitted