[enneff]

The implementation of Pull may be a bit mysterious to the casual reader, but its usage seems clear enough to me from the function signature. Even without reading the docs I think it’s easy to guess what yield, pull, and stop should do (and how to implement yield). That’s what matters, imo.

Fwiw if you look at the source of some other idiomatic standard library functions you may find their implementation is of similar complexity. That’s the nature of good abstractions, though, they should make tricky things easy to use.