[swift-evolution] [Review] SE-0094: Add sequence(initial:next:) and sequence(state:next:) to the stdlib

Dave Abrahams dabrahams at apple.com
Wed May 25 17:27:14 CDT 2016

on Wed May 25 2016, Erica Sadun <erica-AT-ericasadun.com> wrote:

>  On May 25, 2016, at 2:18 PM, Kevin Ballard via swift-evolution <swift-evolution at swift.org> wrote:
>  We think the need to do a capture is icky, so the sequence form is
>  almost always better.
>  I agree that the need for a capture is ugly.
>  The design of AnySequence and AnyIterator dates from a time when the
>  compiler was very immature and many design avenues we might have taken
>  were not available. I find the `sequence` forms to be superior in
>  general, and IMO at some point we should re-evaluate the interfaces to
>  AnySequence and AnyIterator.
>  That sounds like a reasonable justification for keeping sequence(state:next:).
>  -Kevin Ballard
> I think Kevin will agree that I was really slow on uptake in terms of
> the state version, but once I *got* it, I found that I kept using
> it. Yesterday, I was showing someone some math using cubic Beziers,
> and boom there was the extra "var t = 0.0" sitting out there, which I
> immediately recognized and refactored into the sequence(state:next:)
> version instead. It produced a much cleaner and more pleasing result,
> imo. (I also found a dandy playground bug unrelated.)
> I know that the idea of an extra capture mentally feels ugly but it's
> really useful. A week ago, I wouldn't have fought to keep the
> option. Now, I would.

These two paragraphs sound like they're almost saying opposite things.
It's only AnyIterator/AnySequence that makes you create captures.  Care
to clarify?


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