Remove outdated reactive guide and add section about Reactive Streams to flow.md

Author: qwwdfsad

README.md

@@ -62,7 +62,6 @@ suspend fun main() = coroutineScope {
 * Guides and manuals: 
   * [Guide to kotlinx.coroutines by example](https://kotlinlang.org/docs/reference/coroutines/coroutines-guide.html) (**read it first**)
   * [Guide to UI programming with coroutines](ui/coroutines-guide-ui.md)
-  * [Guide to reactive streams with coroutines](reactive/coroutines-guide-reactive.md)
   * [Debugging capabilities in kotlinx.coroutines](docs/debugging.md)
 * [Compatibility policy and experimental annotations](docs/compatibility.md)
 * [Change log for kotlinx.coroutines](CHANGES.md)

coroutines-guide.md

@@ -79,6 +79,7 @@ The main coroutines guide has moved to the [docs folder](docs/coroutines-guide.m
     * <a name='upstream-exceptions-only'></a>[Upstream exceptions only](docs/flow.md#upstream-exceptions-only)
   * <a name='imperative-versus-declarative'></a>[Imperative versus declarative](docs/flow.md#imperative-versus-declarative)
   * <a name='launching-flow'></a>[Launching flow](docs/flow.md#launching-flow)
+  * <a name='flow-and-reactive-streams'></a>[Flow and Reactive Streams](docs/flow.md#flow-and-reactive-streams)
 <!--- TOC_REF docs/channels.md -->
 * <a name='channels'></a>[Channels](docs/channels.md#channels)
   * <a name='channel-basics'></a>[Channel basics](docs/channels.md#channel-basics)

docs/coroutines-guide.md

@@ -28,6 +28,5 @@ In order to use coroutines as well as follow the examples in this guide, you nee
 ## Additional references
 
 * [Guide to UI programming with coroutines](../ui/coroutines-guide-ui.md)
-* [Guide to reactive streams with coroutines](../reactive/coroutines-guide-reactive.md)
 * [Coroutines design document (KEEP)](https://github.com/Kotlin/kotlin-coroutines/blob/master/kotlin-coroutines-informal.md)
 * [Full kotlinx.coroutines API reference](https://kotlin.github.io/kotlinx.coroutines)

docs/flow.md

@@ -58,6 +58,7 @@ class FlowGuideTest {
     * [Upstream exceptions only](#upstream-exceptions-only)
   * [Imperative versus declarative](#imperative-versus-declarative)
   * [Launching flow](#launching-flow)
+  * [Flow and Reactive Streams](#flow-and-reactive-streams)
 
 <!--- END_TOC -->
 
@@ -1794,6 +1795,18 @@ as cancellation and structured concurrency serve this purpose.
 Note that [launchIn] also returns a [Job], which can be used to [cancel][Job.cancel] the corresponding flow collection
 coroutine only without cancelling the whole scope or to [join][Job.join] it.
 
+### Flow and Reactive Streams
+
+For those who are familiar with [Reactive Streams](https://www.reactive-streams.org/) or reactive frameworks such as RxJava and project Reactor, 
+design of the Flow may look very familiar.
+
+Indeed, its design was inspired by Reactive Streams and its various implementations. But Flow main goal is to have as simple design as possible, 
+be Kotlin and suspension friendly and respect structured concurrency. Achieving this goal would be impossible without reactive pioneers and their tremendous work. You can read the complete story in [Reactive Streams and Kotlin Flows](https://medium.com/@elizarov/reactive-streams-and-kotlin-flows-bfd12772cda4) article.
+
+While being different, conceptually, Flow *is* a reactive stream and it is possible to convert it to the reactive (spec and TCK compliant) Publisher and vice versa.
+Such converters are provided by `kotlinx.coroutines` out-of-the-box and can be found in corresponding reactive modules (`kotlinx-coroutines-reactive` for Reactive Streams, `kotlinx-coroutines-reactor` for Project Reactor and `kotlinx-coroutines-rx2` for RxJava2).
+Integration modules include conversions from and to `Flow`, integration with Reactor's `Context` and suspension-friendly ways to work with various reactive entities.
+ 
 <!-- stdlib references -->
 
 [collections]: https://kotlinlang.org/docs/reference/collections-overview.html