on Mon May 09 2016, Joe Groff <jgroff-AT-apple.com> wrote: >> On May 9, 2016, at 6:23 PM, Brent Royal-Gordon via swift-evolution >> <[email protected]> wrote: >> >>> * Operations that depend on sorted-ness and use binary predicates should >>> not be available on all Collections; they're too easy to misuse, >>> they're hard to name well, and as Nicola Salmoria has noted, they > >>> would not make any sense at all for a Set<T>. >>> >>> * They should be scoped to a kind of collection that bundles >>> the predicate with the elements, e.g. >>> >>> let x = Sorted([3, 4, 1, 5, 2], >) // stores a sorted copy of >>> the array >>> let y = Sorted(preSorted: 0..<100, <) // stores a copy of the range >>> >>> Maybe there should also be protocols for this; CountableRange<T> would >>> already already conform to the immutable version. We might want a >>> mutable form of the protocol for sorted collections with >>> insertion/removal methods. This whole area needs more design. >> >> I agree with both of these statements, but not with your conclusion. >> >> There are three classes of collections: >> >> 1) Those which are always sorted, like a SortedSet. >> 2) Those which may or may not be sorted, like an Array. >> 3) Those which are never sorted, like a Set. >> >> These APIs are useless on a #3, but #2 is still a valuable use case >> to support. In particular, it's quite common to use sorted `Array`s, >> and these APIs would help you do that. >> >> What I might consider doing is tying this to >> `RangeReplaceableCollection`. That protocol is applied only to types >> which allow insertion at arbitrary indices, which is a good, though >> not perfect, proxy for types which might allow you to manually >> maintain a sort order. `Array`, `ArraySlice`, `ContiguousArray`, and >> the mutable `String` views would get these methods, while `Set` and >> `Dictionary` would not. > > We could also introduce a new OrderedCollection protocol. (This would > also be useful in the future for supporting `case` pattern matching on > collections. It makes sense to pattern-match arrays and other ordered > collections in order by element, but you'd expect very different > semantics pattern-matching an unordered Set.)
What do you mean by “Ordered” here? Please note that when Cocoa uses “Ordered” it means something very different from “Sorted.” I don't find the Cocoa usage intuitive myself, but it might be best to avoid that term to avoid confusion. -- -Dave _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
