Iterators […] keep their state internally, so it seems there's no way
Yes, and that for a good reason. You cannot clone the state, or otherwise you could tamper too much with the generator.
It might be possible however to create a second iterator that runs alongside of the first one, by memorizing its sequence and yielding it later again. However, there should be only one iterator that really drives the generator - otherwise, which of your clones would be allowed to send next() arguments?
