Meeting C++ 2025 - Using std::generator<> in Practice

Nicolai Josuttis

On Day 1 at 17:15 (CET/Berlin) in Track B [Opal Room and online]

C++20 introduced coroutines, which are functions that can be subspended and later resumed (in the same or a different context). As a consequence, coroutines allow programs to switch back and forth between different paths of execution. However, C++20 only provided low-level support, which is highly flexible but requires a lot of boilerplate code to implement even simple coroutine use cases.

One key element of this boilerplate code are coroutine interfaces, which

• serve as standard customization point for the compiler
  to configure general aspects of the coroutine and
• define the API to deal with the coroutine.

With std::generator<>, C++23 introduces a  first standard coroutine interface for the use cases, where a coroutine generates a sequence of values, which the user(s) of the coroutine can process using a range interface.

This talks introduces the std::generator<> class template, explains how it can be used in practice, provides practical insights about special attributes, and discusses various pitfalls you shouldhave in mind when using coroutines and std::generator<>.

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