Both effects and coroutines can (and typically do) work implicitly across calls like that. The version with forwarding operators like in this post is something

Both effects and coroutines can (and typically do) work implicitly across calls like that. The version with forwarding operators like in this post is something of a Rust-ism, or more generally an async/await-ism, or a stackless coroutine-ism. The more fundamental difference between effects and coroutines is that a `yield` in a coroutine always goes to the one unique resumer, and carries a single type of value. On the other hand, an expression may have several effects, each of which may be handled in a different place, in the same way that distinct exception types may be caught in different places.