[swift-evolution] [Review] SE-0194: Derived Collection of Enum Cases

[Tony Allevato]

On Mon, Jan 8, 2018 at 11:02 AM Douglas Gregor via swift-evolution <
swift-evolution at swift.org> wrote:

> Hello Swift community,
>
> The review of SE-0194 "Derived Collection of Enum Cases" begins now and
> runs through January 11, 2018. The proposal is available here:
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0194-derived-collection-of-enum-cases.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/0194-derived-collection-of-enum-cases.md
>
> Reply text
>
> Other replies
>
>
> <https://github.com/apple/swift-evolution/pull/114#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?
>
> Big +1. I've been looking forward to something like this for a long time.

I'm extremely happy with the API chosen here. ValueEnumerable and allValues
are absolutely the correct names, because the protocol is not *restricted*
to enums, it is merely *synthesized automatically* for enums. That's a very
important distinction. Someone could provide their own conformance to
ValueEnumerable and use it in generic algorithms and have everything work
as expected.

In a perfect world I would argue that the associated type of allValues
should be a Sequence instead of a Collection as this would allow it to be
extended to infinite sequences (i.e., cases with associated values that are
deeply ValueEnumerable), but I'll admit that I've never come up with a
compelling use case for this beyond obscure combinatorial algorithms. Since
getting the count of values is important to many users, Collection is a
reasonable compromise and I don't have any objections.


>
>    - Is the problem being addressed significant enough to warrant a
>    change to Swift?
>
> Yes. It's a frequently requested feature and has utility both in UI-driven
logic (table view sections based on an enum) and other algorithms.



>
>    - Does this proposal fit well with the feel and direction of Swift?
>
> Yes. The API design fits right into other stdlib concepts, and the
conditions for synthesis align with the synthesis of other synthesized
protocols.



>
>    - If you have used other languages or libraries with a similar
>    feature, how do you feel that this proposal compares to those?
>
> Just Java's values() function that is present on all enums. The
functionality provided here is what I would expect, similar to other
languages.



>
>    - How much effort did you put into your review? A glance, a quick
>    reading, or an in-depth study?
>
> An in-depth read and I was heavily involved in some of the earlier
discussion threads.



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