C++20 introduced coroutines. Quasar Chunawala, our guest editor for this edition, gives an overview.

A Guest Editorial

by Quasar Chunawala, Frances Buontempo

From the article:

You’ve likely heard about this new C++20 feature, coroutines. I think that this is a really important subject and there are several cool use-cases for coroutines. A coroutine in the simplest terms is just a function that you can pause in the middle. At a later point the caller will decide to resume the execution of the function right where you left off. Unlike a function therefore, coroutines are always stateful - you at least need to remember where you left off in the function body.

Coroutines can simplify our code! Coroutines are a great tool, when it comes to implementing parsers.

The coroutine return type

The initial call to the coroutine function will produce a return object of a certain ReturnType and hand it back to the caller. The interface of this type is what is going to determine what the coroutine is capable of. Since coroutines are super-flexible, we can do a whole lot with this return object. If you have some coroutine, and you want to understand what it’s doing, the first thing you should look at is the ReturnType, and what it’s interface is. The important thing here is, we design this ReturnType. If you are writing a coroutine, you can decide what goes into this interface.