I recall reading that in Python 3.6 they changed the implementation of set and dict to both have better performance *and* maintain insert order for free. I know nothing about the implementation details of this but might it be possible to make a similar change to Swift’s Set and Dictionary, so that we don’t even need specialized ordered variants?
> On Jun 9, 2017, at 7:28 PM, Douglas Gregor <dgre...@apple.com> wrote: > > >> 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> 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> 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> 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 | @SlaunchaMan | jeffkelley.org >>>>> >>>>>> On Jun 7, 2017, at 2:10 PM, Maik Koslowski via swift-evolution >>>>>> <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 >>>>>> 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 >>>>>> >>>>>> _______________________________________________ >>>>>> swift-evolution mailing list >>>>>> swift-evolution@swift.org >>>>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>>>> >>>>> _______________________________________________ >>>>> swift-evolution mailing list >>>>> swift-evolution@swift.org >>>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>>> _______________________________________________ >>>> swift-evolution mailing list >>>> swift-evolution@swift.org >>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>> _______________________________________________ >>> swift-evolution mailing list >>> swift-evolution@swift.org >>> https://lists.swift.org/mailman/listinfo/swift-evolution >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org >> https://lists.swift.org/mailman/listinfo/swift-evolution >
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
