This uses stackful continuations. I.e. you can nest arbitrary code between setting the handler and invoking an effect. With C++ language-level coroutines, every

This uses stackful continuations. I.e. you can nest arbitrary code between setting the handler and invoking an effect. With C++ language-level coroutines, everything in between would also need to be a coroutine which doesn't compose as well (i.e. this library doesn't suffer from the colored function problem).