Stream API

[Karl]

That also came up during the discussion on post-nil behaviour:

@Lily_Ballard

In fact, I don't think the post-nil behavior of generators is even the biggest potential gotcha. A much bigger issue is how generators behave when you make copies of them. If you ever copy a generator you're supposed to never touch the original again, but it's easy to violate that accidentally, and most generators actually behave sanely when copied anyway.

So my point is that it sure seems like Iterators were designed to be single-pass.