[swift-evolution] Feature proposal: Range operator with step

[Xiaodi Wu]

Sure, I could give it a shot this weekend.
On Wed, Mar 30, 2016 at 12:03 PM Erica Sadun <erica at ericasadun.com> wrote:

>
> On Mar 29, 2016, at 11:26 PM, Xiaodi Wu via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> On Tue, Mar 29, 2016 at 7:48 PM, Dave Abrahams <dabrahams at apple.com>
> wrote:
>
>
> on Tue Mar 29 2016, Xiaodi Wu <xiaodi.wu-AT-gmail.com
> <http://xiaodi.wu-at-gmail.com>> wrote:
>
> Relatedly, while you're tackling this big revision:
>
> I've tried to play around with what it would take to write a generic
> non-error-accumulating striding method, and afaict, it would be
> enormously cleaner if Strideable types are guaranteed to have + and *
> (well, Strideable.Stride needs *, to be more accurate),
>
>
> That should happen automatically, since it conforms to SignedNumber,
> when we get the Integer protocols updated (project currently on hold while
> we land this other revision).
>
> since the iterator needs to be able to compute end = start + iteration
> * stride.
>
>
> Don't you need division too if you're going to do this?
>
>
> I didn't seem to ever need division. See attached playground (which
> borrows shamelessly from existing code and Erica's proposal, and which
> is written in Swift 2.2 because that's what I had handy).
>
>
> Have you considered trying to extend the `swift-3-indexing-model
> <https://github.com/apple/swift/tree/swift-3-indexing-model>` branch
> at the Swift repo to take the floating point approach into account? Dave A
> is working on a massive overhaul of ranges (including `Countable` items
> and one would presume floating point closed and open intervals as well),
> and I'd love to see better implementations of, for example,
>  `(x..<y).striding(by:z)`
> happen for Double types.
>
> I'd be happy to throw a proposal together based on a proof of concept,
> if you had the flexibility to work on the coding.
>
> -- Erica
>
>
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