Coroutines – A Deep Dive

C++ coroutines require implementing several components: a return type with a nested promise_type, coroutine handles for managing execution state, and awaitable objects for suspension points. The promise_type defines behavior at key lifecycle points (startup, completion, yielding) through methods like get_return_object(), initial_suspend(), final_suspend(), and yield_value(). Coroutine handles enable resuming and destroying suspended coroutines. Awaitables control suspension behavior via await_ready(), await_suspend(), and await_resume(). The article walks through building yielding and waiting coroutines from scratch, then introduces C++23's std::generator for simpler implementations like Fibonacci sequences.