On Wed, Jun 29, 2016 at 4:50 PM, David Sweeris <daveswee...@mac.com> wrote:
> That’s the “as proposed” usage for getting the size of a value (from > https://gist.github.com/erica/57a64163870486468180b8bab8a6294e) > > // Types > MemoryLayout<Int>.size // 8 > MemoryLayout<Int>.arraySpacing // 8 > MemoryLayout<Int>.alignment // 8 > // Valuelet x: UInt8 = 5 > MemoryLayout(x).dynamicType.size // 1 > MemoryLayout("hello").dynamicType.arraySpacing // 24 > MemoryLayout(29.2).dynamicType.alignment // 8 > > > > At least, I *thought* that was the latest version of the proposal. Maybe > I’ve gotten confused. > There must be a typo in these examples. `MemoryLayout(x.dynamicType).size` perhaps? > > - Dave Sweeris > > > On Jun 29, 2016, at 4:36 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > > > On Wed, Jun 29, 2016 at 4:29 PM, David Sweeris via swift-evolution < > swift-evolution@swift.org> wrote: > >> (While I was typing this up, I realized that the exact usage you’re >> worried about, “MemoryLayout(Int.self).size” won’t compile, since >> `MemoryLayout` currently doesn’t have instance properties. If you’re >> worried about someone incorrectly typing out >> “MemoryLayout(Int.self).dynamicType.size”, though…) >> >> I made a rather critical typo in my earlier reply. It should’ve been >> “init(_: T.Type)”, instead of “init(_: T.self)”, which is to say this: >> extension MemoryLayout { // assuming `MemoryLayout<T>` is already >> defined as proposed >> public init(_ : T.Type) {} // makes it so that >> `MemoryLayout(T.self)` still has the correct type for `T` >> } >> >> Here are the results of some quick playgrounding in the WWDC Xcode 8 beta: >> // without `init(_ : T.Type)` defined >> MemoryLayout<Int8>.size // 1, correct >> MemoryLayout(Int8.self).dynamicType.size // 8, almost certainly >> wrong >> //MemoryLayout(Int8).dynamicType.size // error >> MemoryLayout(0 as Int8).dynamicType.size // 1, correct >> MemoryLayout<Int8.Type>.size // 8, correct >> MemoryLayout(Int8.Type.self).dynamicType.size // 8, correct, but is >> oddly worded >> //MemoryLayout(Int8.Type).dynamicType.size // error >> >> // with `init(_ : T.Type)` defined >> MemoryLayout<Int8>.size // 1, correct >> MemoryLayout(Int8.self).dynamicType.size // 1, almost certainly >> correct >> MemoryLayout(Int8).dynamicType.size // 1, almost certainly >> correct >> MemoryLayout(0 as Int8).dynamicType.size // 1, correct >> MemoryLayout<Int8.Type>.size // 8, correct >> MemoryLayout(Int8.Type.self).dynamicType.size // 8, correct, but is >> oddly worded >> MemoryLayout(Int8.Type).dynamicType.size // 8, correct >> >> The only value that changes (aside from the errors) is the one “typo” >> that you were worried about. >> >> Do this change your mind? >> > > These examples make no sense to me. Why are we asking for the size of the > dynamicType of MemoryLayout? > > >> >> >> >> On Jun 29, 2016, at 12:34 PM, Dave Abrahams <dabrah...@apple.com> wrote: >> >> >> >> on Wed Jun 29 2016, David Sweeris <davesweeris-AT-mac.com >> <http://davesweeris-at-mac.com/>> wrote: >> >> Would adding a "init(_: T.self) {...}" solve that issue? >> >> >> ? I don't see how. >> >> >> Sent from my iPhone >> >> On Jun 29, 2016, at 01:54, Dave Abrahams via swift-evolution < >> swift-evolution@swift.org> wrote: >> >> My worry is that people will write >> >> MemoryLayout(Int.self).size >> >> when they mean >> >> MemoryLayout<Int>.size >> >> (often because for some reason they don't like angle brackets). >> >> I prefer to make the uncommon case much harder to write. >> >> >> -- >> Dave >> >> >> >> - Dave Sweeris >> >> >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org >> https://lists.swift.org/mailman/listinfo/swift-evolution > > >
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