[swift-evolution] [Review] SE-0191: Eliminate IndexDistance from Collection

[Tony Allevato]

On Mon, Nov 27, 2017 at 5:34 PM Douglas Gregor via swift-evolution <
swift-evolution at swift.org> wrote:

> Hello Swift community,
>
> The review of SE-0191 "Eliminate IndexDistance from Collection" begins now
> and runs through December 3, 2017. The proposal is available here:
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0191-eliminate-indexdistance.md
>
> Reviews are an important part of the Swift evolution process. All reviews
> should be sent to the swift-evolution mailing list at
>
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
> or, if you would like to keep your feedback private, directly to the
> review manager. When replying, please try to keep the proposal link at the
> top of the message:
>
> Proposal link:
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0191-eliminate-indexdistance.md
>
> Reply text
>
> Other replies
>
> <https://github.com/apple/swift-evolution#what-goes-into-a-review-1>What
> goes into a review?
>
> The goal of the review process is to improve the proposal under review
> through constructive criticism and, eventually, determine the direction of
> Swift. When writing your review, here are some questions you might want to
> answer in your review:
>
>    - What is your evaluation of the proposal?
>
> Emphatically support.


>
>    - Is the problem being addressed significant enough to warrant a
>    change to Swift?
>
> Absolutely. In Swift's earlier days I tried writing a handful of
interesting collection algorithms as generally as possible, but I think I
almost always found myself adding "where IndexDistance == Int" to each one.
Once you start to do anything more interesting than linear traversal (e.g.,
binary search or percentiles), you really need to be working with concrete
integral types.

I've certainly been one on this list advocating for protocols to be "no
more specific than they need to be", and it might be possible to get
further along in the above cases nowadays by constraining to Numeric or
BinaryInteger—I haven't tried since it was introduced—but I'm not sure that
alone holds its weight. If other stdlib algorithms would break with non-Int
distances, the increase in difficultly of writing generic collection
algorithms probably isn't worth it.


>
>    - Does this proposal fit well with the feel and direction of Swift?
>
> Yes. It makes collection algorithms more approachable.


>
>    - If you have used other languages or libraries with a similar
>    feature, how do you feel that this proposal compares to those?
>    - How much effort did you put into your review? A glance, a quick
>    reading, or an in-depth study?
>
> Read the proposal and loosely followed the earlier e-mail discussion.


> More information about the Swift evolution process is available at
>
> https://github.com/apple/swift-evolution/blob/master/process.md
>
> Thank you,
>
> -Doug
>
> Review Manager
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
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