[swift-evolution] [Review] SE-0065 A New Model for Collections and Indices
dabrahams at apple.com
Tue Apr 12 17:43:41 CDT 2016
Thanks for your review, Tony!
on Mon Apr 11 2016, Tony Parker <swift-evolution at swift.org> wrote:
>> On Apr 10, 2016, at 2:41 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
>> Hello Swift community,
>> The review of "A New Model for Collections and Indices" begins now and runs through April 18th. The proposal is available here:
>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at:
>> or, if you would like to keep your feedback private, directly to the review manager.
>> 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?
> I agree with the general direction and scope of the proposal, but I
> think the names could use some changes. Specifically, I don’t think
> the fallback to ‘form’ is required.
It's not a fallback whatsoever. The updated guidelines referenced from
(which was accepted this morning; announcement forthcoming) make the
“form” prefix a first-class citizen that one chooses based on the
noun-ness of the underlying operation. Furthermore, *treating*
“formXXX” as a fallback and avoiding it will continue to strengthen the
sense that it's not something we should normally use, leading to more
naming arguments in the future. It's a strong guideline and as long as
we have it, we shouldn't be afraid to apply it, thereby increasing
uniformity and predictability.
[To all my fellow “InPlace” lovers out there: yes, another guideline
might be more optimal, but this is the guideline we have/can get].
> It would be a significant readability improvement to use a meaningful
> verb to describe the action of altering the argument. The methods that
> create new indices probably need a label on the first argument,
> because otherwise it looks as if the IndexDistance is what is
> described by ‘index’.
> func successor(of i: Index) -> Index
> func formSuccessor(i: inout Index)
> Instead, I suggest:
> func successor(of i : Index) -> Index
> func advance(i: inout Index)
Why is that an improvement? It loses the correspondence between the
operations, which are still a mutating/nonmutating pair. What's it got
to recommend it? I have the same question about all of the suggestions
> func index(n: IndexDistance, stepsFrom i: Index) -> Index
> func index(n: IndexDistance, stepsFrom i: Index, limitedBy limit: Index) -> Index
> func formIndex(n: IndexDistance, stepsFrom i: inout Index)
> func formIndex(n: IndexDistance, stepsFrom i: inout Index, limitedBy limit: Index)
> Suggested (taking into account Nate’s suggestion of reversing the order):
> func index(startingAt i: Index, movedBy n: IndexDistance) -> Index
> func index(startingAt i: Index, movedBy n: IndexDistance, limitedBy limit: Index) -> Index
I find Nate Cook's concerns about the use of “index” here (a mental
clash with unrelated methods having the same basename) especially
convincing. So I think I want to look for other names for these.
> func move(i : inout Index, by n: IndexDistance)
> func move(i : inout Index, by n: IndexDistance, limitedBy limit: Index)
> func predecessor(of i: Index) -> Index
> func formPredecessor(i: inout Index)
> func predecessor(of i: Index) -> Index
> func reverse(i: inout Index)
> I think reversing an index has some nice symmetry with reversing a
> sequence, but if it seems to confusing, then replace advance and
> reverse with ‘moveForward’ and ‘moveBackward’.
Yeah, I don't think moving an index one step backwards could reasonably
be called “reversing” it. “moveBackward” is reasonable, if one wanted
have to break the relationship with predecessor.
> - Tony
>> * Is the problem being addressed significant enough to warrant a change to Swift?
>> * Does this proposal fit well with the feel and direction of Swift?
>> * If you have you 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?
>> More information about the Swift evolution process is available at
>> Thank you,
>> -Chris Lattner
>> Review Manager
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