> On Jun 9, 2017, at 10:19 AM, Xiaodi Wu via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> Let me try to redirect this conversation, if I may.
>
> As far as I can tell, SE-0069 states plainly that the plan of record is to
> offer a value type called OrderedSet in Foundation, but resources to design
> and implement were not then available.
>
> So, little point in having a vote as to whether one is in favor of OrderedSet
> or not. In my view, the questions to be answered are:
>
> For the core team–
>
> * Is it still the plan to offer value types postponed from SE-0069 as a
> future addition to Foundation?
*I* think it’s still a good idea, and I suspect that others on the core team
will agree.
> * If so, is that a priority in the Swift 5 timeframe, and how can the
> community help to bring about this addition?
I wouldn’t consider it a “priority”, in the sense that I can’t imagine anything
in Swift 5 that would absolutely require us to introduce this functionality in
that time frame. It’s a bit of a nice-to-have-at-any-point, noting of course
that bridging NSOrderedSet in existing APIs is a nontrivial source-breaking
change.
Having a proposed API and implementation on hand makes it easier to add this
functionality, of course.
> If not, for the whole community–
>
> * Is it wise to implement such a type in the standard library? Should we
> simply bring over the native implementation from Swift Package Manager? What
> are the implications for bridging?
Obviously, we’d want an efficient copy-on-write, native implementation; the
Swift Package Manager implementation is a bit more bare-bones than we’d want:
absolute performance matters, so having a separate Set + Array in the struct
probably isn’t good enough. Bridging performance matters, so we’d probably want
the one-pointer representation like array uses where the pointer can be vended
directly to Objective-C.
- Doug
> On Fri, Jun 9, 2017 at 11:38 Remy Demarest via swift-evolution
> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
> +1 for ordered set and dictionary, and please add ordered dictionary in ObjC
> as well.
>
> Envoyé de mon iPhone
>
> Le 9 juin 2017 à 03:11, Robert Bennett via swift-evolution
> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> a écrit :
>
>> +1, and would also like to see OrderedDictionary as well.
>>
>> On Jun 9, 2017, at 12:50 AM, Jeff Kelley via swift-evolution
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>
>>> I would be in favor of it; there have been a few times (including Core
>>> Data, as you mentioned) where I would have used it had it been available.
>>>
>>>
>>> Jeff Kelley
>>>
>>> slauncha...@gmail.com <mailto:slauncha...@gmail.com> | @SlaunchaMan
>>> <https://twitter.com/SlaunchaMan> | jeffkelley.org <http://jeffkelley.org/>
>>>> On Jun 7, 2017, at 2:10 PM, Maik Koslowski via swift-evolution
>>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> in the past there have been a few requests for an OrderedSet
>>>> implementation in Swift. In the proposal
>>>> https://github.com/apple/swift-evolution/blob/master/proposals/0069-swift-mutability-for-foundation.md
>>>>
>>>> <https://github.com/apple/swift-evolution/blob/master/proposals/0069-swift-mutability-for-foundation.md>
>>>> was mentioned that the OrderedSet will be considered for the feature.
>>>>
>>>> However, since then there were a few discussions on OrderedSet but it
>>>> doesn’t get much attention and there wasn’t any comment about it from the
>>>> swift team.
>>>>
>>>> I want to bring up some points, why an OrderedSet is needed in the base
>>>> library.
>>>>
>>>> 1. CoreData is probably the most obvious place where people would use an
>>>> ordered set. Especially when working with large amounts of data,
>>>> presorting can save a lot of time and battery life. If a bridgeable
>>>> ordered set was part of the standard library we could use a ordered set in
>>>> swift without having to use the NSOrderedSet from objective c. Which would
>>>> be pretty nice in my opinion. Even when using a NSOrderedSet we couldn’t
>>>> have a generic version of it.
>>>>
>>>> 2. A shared datamodel between App and Server. One main advantage of having
>>>> web servers written in Swift is that we can share code between the server
>>>> and the app. For servers performance does matter a lot, since they are
>>>> usually working with much more data than apps. Databases are represented
>>>> as sets and fetching sorted data from the database can be represented as
>>>> an ordered set. However, since we don’t have ordered sets we have to
>>>> choose either a normal set or an array. Sets don’t have an order and
>>>> arrays can contain the same object multiple times, which makes them both a
>>>> less suitable choice.
>>>>
>>>> 3. Swift has the potential to be used for education. There is a lot of
>>>> support, for example the playground app on iPad. When it comes to the
>>>> theory behind data structures and algorithms or to the theory of
>>>> computation a defined order plays an important role.
>>>>
>>>> The biggest issue is that we always have to copy data from a set into an
>>>> array to have it in a sorted order with losing the safety of uniqueness.
>>>> Which is not suitable for a safe and performance oriented programming
>>>> language at all.
>>>>
>>>> Last but not least, it fits in the goals of Swift 4 stage 2 and an ordered
>>>> set can be found in other popular programming languages, too.
>>>>
>>>> What do you think?
>>>>
>>>> Best regards,
>>>>
>>>> Maik
>>>>
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>>>
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