How about: let results = possibilities.where(matching: closure)
:) l8r Sean Sent from my iPad > On Jun 22, 2016, at 8:00 PM, Xiaodi Wu via swift-evolution > <swift-evolution@swift.org> wrote: > > filter(extractingWhere:) >> On Wed, Jun 22, 2016 at 18:53 Dave Abrahams via swift-evolution >> <swift-evolution@swift.org> wrote: >> >> on Wed Jun 22 2016, Xiaodi Wu <swift-evolution@swift.org> wrote: >> >> > I'll duly oblige with some pushback on `suchThat`. I get that you're trying >> > to clarify whether filter retains or gets rid of elements that match the >> > predicate, but I don't think "filter such that" expresses this idea at all. >> > >> > Comparing to "filter where," "filter such that" is equally susceptible to >> > misinterpretation that you are filtering to remove elements that are >> > matched. For example: "find me some apples, filtering such that are >> > bruised." >> >> Hahaha, that's a very different interpretation of “such” that I hadn't >> considered! OK, suppose it was “soEach:” ? >> >> let primes = xs.filter(soEach: isPrime) >> >> > I'd suggest that if you want to be perfectly clear, you'd need something >> > like `filter(keepingWhere:)`. >> >> let primes = xs.filter(keepingWhere: isPrime) >> >> A slight problem is that filter is nonmutating, so all elements are >> “kept.” But maybe that's just Dave being overly concerned with unlikely >> misinterpretations at the cost of “naturalness.” >> >> Further thoughts? >> >> > On Wed, Jun 22, 2016 at 18:33 Dave Abrahams via swift-evolution < >> > swift-evolution@swift.org> wrote: >> > >> >> >> >> on Tue Jun 21 2016, Dave Abrahams <swift-evolution@swift.org> wrote: >> >> >> >> > on Mon Jun 20 2016, Brent Royal-Gordon <swift-evolution@swift.org> >> >> wrote: >> >> > >> >> >>> A couple of weeks ago we started to notice that we had some >> >> poorly-named >> >> >>> closure parameters and argument labels in the standard library, so we >> >> >>> did a complete audit of the standard library's APIs and came up with a >> >> >>> preliminary proposal for changes, which we applied in a branch and you >> >> >>> can review in https://github.com/apple/swift/pull/2981. Let's please >> >> >>> carry on further discussion here rather than in the pull request, >> >> though. >> >> >> >> >> >> In general, I like this; `orderingBy` is a particularly nice >> >> >> improvement over the old `isOrderedBefore` convention. >> >> > >> >> > I don't really love the use of “by”, FWIW, but I thought `orderingWith` >> >> > was more confusable (ordering A with B might swap A and B, whereas the >> >> > parameter is a closure). It could be argued, though, that I am being >> >> > overly concerned with unlikely misinterpretations, at the cost of >> >> > “naturalness”—a known weakness of mine ;-). Anyway, as ever I'm open to >> >> > discussion on this. >> >> > >> >> >> A few specific comments about things I don't like: >> >> >> >> >> >> * In `map` and `flatMap`, I'm not sure how much `transform` buys us >> >> >> over `elementTransform`. >> >> > >> >> > I think you mean the converse. And I agree that `elementTransform` >> >> > is probably not an improvement over `transform`. >> >> >> >> ...and I've gone back to `transform` in my PR. >> >> >> >> >> * In general, I'm not a fan of most of the changes away from `where` >> >> >> labels. >> >> > >> >> > The only such changes I can find are in >> >> > >> >> https://github.com/apple/swift/pull/2981/commits/3418eede88d724ad23731fe8f412f51e03cf5106 >> >> > >> >> > Note that part of this change was to make all filter closures >> >> > consistent; in the main `filter` API there was no label at all. >> >> > However, we felt that there's a real clarity problem with the polarity >> >> > of the argument (we talk about “filtering things out” but the closure >> >> > indicates which elements to keep). And we couldn't find a “where”-based >> >> > name that began to clarify it. >> >> > >> >> > I will argue that even changing to “suchThat,” as in the PR, does not >> >> > sufficiently clarify the closure's polarity, and the only true fix for >> >> > filter is to use a different base name (some have suggested “select,” >> >> > and I have other ideas), but that is out of scope for this particular >> >> > set of changes. So if the community is happier with a “where” label >> >> > here I can live with it. I do think “suchThat” is marginally clearer. >> >> >> >> I have not received any further pushback on “suchThat,” so I've left it >> >> alone. >> >> >> >> > >> >> >> Those are a nice, straightforward convention applied broadly across >> >> >> the Sequence APIs. (Yes, I criticized `where` as a method name in >> >> >> another thread, but I don't think `where` is a problem when there's a >> >> >> function base name to give it context.) When they don't work, that's >> >> >> usually because of a less-than-ideal base name. I'm not saying that >> >> >> *all* base names that aren't compatible with `where` should be >> >> >> changed, but rather that if `where` is not enough, that's an API >> >> >> smell. >> >> >> >> >> >> * In particular, `elementWhere` is not a good label for the same >> >> >> reason that `removeElement` is not a good name. Session 403 last week >> >> >> actually talked about this between roughly minutes 8 and 11. (I'm sure >> >> >> you know about its content; you probably saw it before we did.) >> >> > >> >> > Yes I do, and I think you misinterpreted the message in that session. >> >> > There's nothing wrong with repeating type information when it's >> >> > necessary for clarity or fluency at the use-site. In the case of >> >> > `contains(elementWhere:)`, it's there for fluency: >> >> > >> >> > customers.contains(where: isSingle) >> >> > >> >> > doesn't read as well as: >> >> > >> >> > customers.contains(elementWhere: isSingle) >> >> > >> >> > The point is not to imagine that every argument should be preceded by >> >> > a noun, and repetition of type information is often the result of >> >> > trying to do that. >> >> > >> >> >> * I like `separatedWhere` on `split`, but I think the Equatable >> >> >> version needs a similar renaming. >> >> > >> >> > That's a nice thought; I think it's arguably out-of-scope here, though. >> >> > >> >> >> Perhaps `separatedBy`? `separatedOn`? The usual opposite of `where`, >> >> >> `of`, doesn't work here. (Alternatively, `separatedWhere` could be >> >> >> `separatorWhere` instead, but that's not quite as elegant.) >> >> > >> >> > I'd want to consider variations of `separatingAt` or `onSeparator` or >> >> > `atSeparator` too... which makes me thing “separatedWhere” might not be >> >> > as good as “separatingWhere” for the closure version. >> >> > >> >> >> * I'm very uncomfortable with the amount of weight >> >> >> `accumulatingResultBy` adds to `reduce`. `combinedBy` seems perfectly >> >> >> cromulent to me. I'm even more concerned by your suggestion in the >> >> >> pull request body of >> >> >> `accumulating(startingFrom:combiningBy:)`. `reduce` is a subtle and >> >> >> slightly confusing operation; adding more words to its call sites will >> >> >> not solve that problem. If you want to invent a new name from whole >> >> >> cloth, I would probably use something like `combining(with >> >> >> initialResult: T, by nextResult: (T, Element) -> T)`. (For that >> >> >> matter, while we're working in this area, `sequence(first:next:)` >> >> >> could use a similar coat of paint.) >> >> > >> >> > As with `filter(suchThat:`, `reduce(accumulatingResultBy:` is attempting >> >> > to solve with an argument label what IMO is a grave weakness in clarity >> >> > of the base name. If you read the documentation for `reduce`, you'll >> >> > see that it's all about accumulating a result, and if you consider that >> >> > its current signature often leads to O(N^2) behavior and we are thinking >> >> > about adding an overload that takes its “accumulator” inout, the >> >> > arguments for avoiding the name “accumulate” get progressively weaker. >> >> > But as noted earlier, changing base names is out-of-scope for this >> >> > proposal. As with “filter,” I could live with leaving this alone, >> >> > though I do believe “accumulatingResultBy:” is a real improvement in >> >> > clarity. >> >> >> >> ...but I think it's overly specific at the expense of smoothness. So >> >> I've removed `Result` from that name. >> >> >> >> >> * I agree with the comment on GitHub that `invoke` should be >> >> >> `execute`. >> >> > >> >> > Why? Rationales help. >> >> > >> >> >> If you see a distinction between the two cases on the number of >> >> >> arguments, I would then suggest `passTo` as the label on these >> >> >> methods: `views.forEach(passTo: addSubview)`, >> >> >> `withUnsafeBufferPointer(&bytes, passTo: Data.init(buffer:))`. >> >> > >> >> > Those are intriguing ideas, but that direction tends to suggest this >> >> > would be better: >> >> > >> >> > views.passEach(to: addSubview) >> >> > passUnsafeBufferPointer(to: Data.init(buffer:)) >> >> > >> >> > ...until you pass a trailing closure: >> >> > >> >> > views.passEach { addSubView($0) } >> >> > passUnsafeBufferPointer { Data.init(buffer:$0) } >> >> > >> >> > (note: withUnsafeBufferPointer takes only one argument, a closure). >> >> > >> >> >> >> >> >> * It's a little odd that you're using `comparingBy` for `Equatable` >> >> >> and `orderingBy` for `Comparable`. Did you judge `equatingBy` to be >> >> >> too awkward? >> >> > >> >> > Yes, and because it's not “equating,” which would mean using equality >> >> > (==) it's “testing equivalence” with respect to the predicate. >> >> > >> >> >> Perhaps the real problem is that `Equatable` ought to be `Comparable` >> >> >> and `Comparable` ought to be `Orderable`? >> >> > >> >> > I don't think so, personally, but regardless I consider such a change >> >> > out-of-scope for this proposal. >> >> > >> >> >> Or maybe `comparingBy` should just be something more general, like >> >> >> `matchingBy`? That would make perfectly sensible but slightly odd use >> >> >> cases like this one read better: >> >> >> >> >> >> let isAnIdiot = luggageCombination.starts(with: [1, 2, 3, 4, >> >> >> 5], matchingBy: <=) // Matches [1,2,3,4,5], but also [1,1,1,1,1], >> >> >> [1,2,3,2,1], etc. >> >> > >> >> > That would not be legal, as <= is not an equivalence relation. You >> >> > could think about redefining the meaning of `starts(with:` to not >> >> > require an equivalence relation, but that's something I'm not confident >> >> > *I* know how to do meaningfully, and regardless is again out-of-scope. >> >> > >> >> >> Very soon (hopefully), I will be posting an early draft of a proposal >> >> >> renaming the various first/last/prefix/suffix/etc. APIs. I believe the >> >> >> only place it touches on your proposal is in >> >> >> `starts(with:isEquivalent:)`, but I think your changes to the second >> >> >> parameter label can be easily incorporated into what I'm doing. >> >> > >> >> > Great! >> >> >> >> I'm going to write up the proposal ASAP based on the current PR unless I >> >> get more feedback. >> >> >> >> Thanks, >> >> >> >> -- >> >> Dave >> >> >> >> _______________________________________________ >> >> 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 >> > >> >> -- >> Dave >> >> _______________________________________________ >> 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
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