It seems like a different kind of boilerplate: instead the functions need to take a yield so you are threading the function through you program. I don't know if

It seems like a different kind of boilerplate: instead the functions need to take a yield so you are threading the function through you program. I don't know if it's better to expect a return type or to force a function argument. I lean towards the former, but that might be because of familiarity.