Coroutines in Kotlin Andrey.Breslav@JetBrains.com This talk could have been named… • async/await/yield • fibers • [stackless] continuations Suspendable Computations Outline • Motivation/Examples languages • Kotlin’s Solution – Client code – Library code • Compiling Coroutines • Exception Handling • Appendix. Serializable Coroutines? “Legal” • All I’m saying is no more final than Valhalla J val image flexibility for library designers – with minimal runtime support – and no macros J Flavors of Coroutines Stackless Stackful Language restrictions Use in special contexts L Use anywhere J Implemented

From Functions to Coroutines 40 Years Evolution Rainer Grimm Training, Coaching, and Technology Consulting www.ModernesCpp.netEvolution of Callable template T invoke(Func

2/55 Deciphering Coroutines - Part 2 Mastering Asynchronous Control Flow Andreas Weis CppCon 20243/55 About me - Andreas Weis (he/him) ComicSansMS cpp@andreas-weis.net Co-organizer of the Munich best-practice talk.16/55 A mental model for coroutines: Cooperative Threads void spawn_task () { // ... Result r = outer_function (); }16/55 A mental model for coroutines: Cooperative Threads void spawn_task mental model for coroutines: Cooperative Threads PartialResult middle_function () { auto r = inner_function (); return PartialResult :: from_io_result (r); }16/55 A mental model for coroutines: Cooperative

Challenges when onboarding coroutines A lot of existing code mostly callback-based A custom-built I/O event loop predates Asio by a decade fine-tuned for specific use cases Somewhat conservative conservative audience real benefit needs to be demonstrated to justify switchingCallbacks vs coroutines // read length auto len = make_unique(); async_read(socket, buffer(len.get(), sizeof(int32_t)) use_awaitable); // ...handle data... Local variable Manual lifetime managementCallbacks vs coroutines // read length auto len = make_unique(); async_read(socket, buffer(len.get(), sizeof(int32_t))

Jeffrey E. Erickson cppcon 2023 1cppcon 2023 Behavioral Modeling in HW/SW Co-design using C++ coroutines Jeffrey E Erickson, Ph.D. Sebastian Schönberg, Ph.D.© 2023 Intel Corporation and Jeffrey E. Erickson Jeffrey E. Erickson cppcon 2023 8 Coroutines are an enabling language feature • To date, coroutines have been about execution and workloads • In the modeling context, coroutines… • Provide syntactic sugar Handle parallelism in a way that isn’t clunky • Scale across large and complex HW interactions But, coroutines lack comprehensive standard library support • We used concurrencppIntel Confidential Department

knowledge Francesco Zoffoli - Coroutine Patterns and How to Use Them - CppCon 2023 5Motivation Coroutines introduce new paradigm Francesco Zoffoli - Coroutine Patterns and How to Use Them - CppCon 2023 CppCon 2023 11Overview – Executor • Executes synchronous functions • Could be multi-threaded • Coroutines are split in synchronous functions Francesco Zoffoli - Coroutine Patterns and How to Use Them CppCon 2023 19 [1] https://ericniebler.com/2020/11/08/structured-concurrency/Lifetime Member coroutines implicitly capture this Francesco Zoffoli - Coroutine Patterns and How to Use Them - CppCon

longer period Kotlin/JVM Kotlin/Native Kotlin/JS Kotlin Gradle plugin Standard library Tools Coroutines 1.6.0-RC Migrating to Kotlin 1.6.0 What's new in Kotlin 1.5.30 Language features Kotlin/JVM Stable JSON serialization Scripting and REPL Migrating to Kotlin 1.4.0 What's new in Kotlin 1.3 Coroutines release Kotlin/Native Multiplatform projects Contracts Capturing when subject in a variable JVM backend JavaScript backend Tools What's new in Kotlin 1.1 Table of contents JavaScript Coroutines (experimental) Other language features Standard library JVM Backend JavaScript backend Kotlin

Development Using Kotlin for Android Development Kotlin JavaScript Overview Kotlin/Native for Native Coroutines for asynchronous programming and more Multiplatform Programming What's New in Kotlin 1.1 What's interoperability Kotlin/Native interoperability with Swift/Objective-C Kotlin/Native Gradle plugin Coroutines Table of contents Coroutine basics Table of contents Additional references Table of contents properties, help build powerful and easy-to-use abstractions. Scalability: Kotlin's support for coroutines helps build server-side applications that scale to massive numbers of clients with modest hardware

Android Development Kotlin JavaScript Overview Kotlin/Native for Native Kotlin for Data Science Coroutines for asynchronous programming and more Multiplatform Programming What's New in Kotlin 1.1 What's Kotlin/Native interoperability with Swift/Objective-C CocoaPods integration Kotlin/Native Gradle plugin Coroutines Table of contents Additional references Coroutine Basics Cancellation and Timeouts Composing properties, help build powerful and easy-to-use abstractions. Scalability: Kotlin's support for coroutines helps build server-side applications that scale to massive numbers of clients with modest hardware