Once upon a time coroutines were introduced to Kotlin and they were lightweight. We could launch a multitude of coroutines and we needed a way to communicate between those coroutines without running into a dreaded “mutable shared state” problem. Thus Channel was added as an inter-coroutine communication primitive. The channels…

At the dawn of software engineering computers were programmed directly in machine code, then in assembly, and only later in higher-level languages. Computers are imperative. They operate by executing instructions that mutate their state, stored in registers and memory. Naturally, the same was true about programming languages. In the old…

Repetitio est mater studiorum (Latin, repetition is the mother of all learning). Repetition is great for study, but a bane of software development. Repetitive code is boring and error-prone. Let’s look at a hypothetical example inspired by imperative UI frameworks that are still being used a lot nowadays, even though…

What are Kotlin Exceptions and how should you use them? To figure it out let’s look at their origins first. Exceptions came to Kotlin from Java. The story with exceptions in Java is complicated, though. I’ll give a brief overview. The Origin Java has a unique concept of checked exceptions that were…

Threads are heavy-weight and have substance. With threads, we can get a reference to some kind of current Thread object, examine its properties, modify its thread-local variables, and otherwise manipulate it. It is no surprise that people with the thread-programming background and education, who are coming to programming with coroutines…

Kotlin Coroutines are typically used for asynchronous programming. However, the underlying design of coroutines and their implementation in Kotlin compiler are quite universal, solving problems beyond asynchronous programming. Let’s take a look at one such problem that can be elegantly solved with coroutines— writing deeply recursive functions. Setup Consider a tree…

Throughout most of my early professional career, I programmed in languages where you terminate or separate statements with a semicolon; it was like an ideograph distinguishing coders from laypeople. I had a motor reflex to type a semicolon (;) without having to think about it. So when I got involved…

When we work on a piece of software, being it an application or a library, we often focus on its functional requirements. They are usually quite easy to directly observe and test; functional requirements are featured in software marketing materials in the form of “feature matrix” that compares different products…

A little over a year ago I announced big conceptual shift in the design of Kotlin Coroutines called Structured Concurrency. From that moment on, it took our team about a month to make the first stable 1.0.0 release of kotlinx.coroutines library. After a year of further work, kotlinx.coroutines had added…