<div dir="ltr">On Fri, Jul 22, 2016 at 9:38 PM, <span dir="ltr"><<a href="mailto:jaden.geller@gmail.com" target="_blank">jaden.geller@gmail.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div></div><div>This seems reasonable to me. I don't see why `===` has to do a total order comparison when we already have another operator, `<=>`, that does that.</div></div></blockquote><div><br></div><div>I take it back. It wouldn't solve the issue that generic `<` would still behave in surprising ways, where two equal floating point values represented differently might be less than each other or greater than each other. I think what we really want is all identity and comparison divorced from IEEE totalOrder.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div><div class="h5"><div>On Jul 22, 2016, at 7:35 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">On Fri, Jul 22, 2016 at 9:28 PM, Dave Abrahams <span dir="ltr"><<a href="mailto:dabrahams@apple.com" target="_blank">dabrahams@apple.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div><div><br>
on Fri Jul 22 2016, Xiaodi Wu <<a href="http://xiaodi.wu-AT-gmail.com" rel="noreferrer" target="_blank">xiaodi.wu-AT-gmail.com</a>> wrote:<br>
<br>
> On Fri, Jul 22, 2016 at 9:13 PM, Matthew Johnson <<a href="mailto:matthew@anandabits.com" target="_blank">matthew@anandabits.com</a>><br>
> wrote:<br>
><br>
>><br>
>> On Jul 22, 2016, at 9:10 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:<br>
>><br>
>> On Fri, Jul 22, 2016 at 9:08 PM, Matthew Johnson <<a href="mailto:matthew@anandabits.com" target="_blank">matthew@anandabits.com</a>><br>
>> wrote:<br>
>><br>
>>><br>
>>> On Jul 22, 2016, at 9:04 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:<br>
>>><br>
>>> On Fri, Jul 22, 2016 at 8:57 PM, Matthew Johnson <<a href="mailto:matthew@anandabits.com" target="_blank">matthew@anandabits.com</a>><br>
>>> wrote:<br>
>>><br>
>>>><br>
>>>> On Jul 22, 2016, at 8:54 PM, Xiaodi Wu via swift-evolution <<br>
>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
>>>><br>
>>>> On Fri, Jul 22, 2016 at 8:52 PM, Jaden Geller via swift-evolution <<br>
>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
>>>><br>
>>>>> "The totalOrder predicate will order these cases, and it also<br>
>>>>> distinguishes between different representations of NaNs and between the<br>
>>>>> same decimal floating point number encoded in different ways."<br>
>>>>> - [Wikipedia](<br>
>>>>> <a href="https://en.wikipedia.org/wiki/IEEE_floating_point#Total-ordering_predicate" rel="noreferrer" target="_blank">https://en.wikipedia.org/wiki/IEEE_floating_point#Total-ordering_predicate</a><br>
>>>>> )<br>
>>>>><br>
>>>>> Sounds like `===` should not return `true` for zeros of different<br>
>>>>> signs, then.<br>
>>>>><br>
>>>><br>
>>>> Fair enough; the result of that will be, as Pyry noted above, that:<br>
>>>><br>
>>>> ```<br>
>>>> [-0.0, 1.0, .nan, 0.0].firstIndex(of: 0.0) //=> 3, not 0<br>
>>>> ```<br>
>>>><br>
>>>><br>
>>>> Maybe we need floating point specific implementations of some algorithms<br>
>>>> to resolve this problem?<br>
>>>><br>
>>>> It doesn’t seem like there is a way to provide the semantics required by<br>
>>>> generic algorithms and still provide the expected behavior for floating<br>
>>>> point values.<br>
>>>><br>
>>><br>
>>> Well, what I'm trying to say is that generic algorithms such as<br>
>>> `index(of:)` require only an equivalence relation. For floating point<br>
>>> types, there are three ways to slice it:<br>
>>><br>
>>> 1. NaN != NaN and +0 == -0 [what the traditional comparison operators are<br>
>>> constrained to do]<br>
>>> 2. NaN == NaN, +0 == -0, and the same number encoded different ways<br>
>>> compare equal<br>
>>> 3. NaN == NaN, +0 != -0, and the same number encoded different ways<br>
>>> compare not equal<br>
>>><br>
>>> Both #2 and #3 can fall out of valid equivalence relations; if `===`<br>
>>> behaved like #2 for FloatingPoint types, then generic algorithms work just<br>
>>> fine. If we insist on using a total ordering defined by `<=>` all the time,<br>
>>> then we've got problems.<br>
>>><br>
>>><br>
>>> And if we don’t then we’re back to 3 different concepts of equality.<br>
>>> There is definitely a tradeoff no matter what we choose.<br>
>>><br>
>><br>
>> If some types have three concepts of equality, each with their particular<br>
>> use, why must we eliminate one of them?<br>
>><br>
>><br>
>> This isn’t about eliminating concepts of equality for a type. They can<br>
>> have 42 if they want.<br>
>><br>
>> This is about the right way to define the semantics of specific<br>
>> protocols. It says nothing about additional notions of equality a type may<br>
>> have available.<br>
>><br>
>> The difficulty is finding a design for the protocols that makes sense with<br>
>> floating point types because we want them to be able to conform to the<br>
>> protocols.<br>
>><br>
><br>
> Agreed. My argument is that if a Comparable can define its own `===`, still<br>
> supplying a valid equivalence relation but not being constrained by a<br>
> contract that `(a <=> b) == .same` iff `a === b`, then we are good to go<br>
> with floating point types.<br>
<br>
</div></div>How would that work? Can you spell out the implications, show how <=><br>
and === would be implemented, and describe what it would mean for<br>
algorithms?<span><br></span></blockquote><div><br></div><div>Right. I'm not married to this solution anymore, but I do think it could work. There would still be a relationship required between `===` and `<=>`. Namely:</div><div><br></div><div>`a === b` if `(a <=> b) == .same`</div><div><br></div><div>But for some values a and b, it is permitted that `a === b && (a <=> b) != .same`. That is, two identical values may be ordered in a total ordering based on *inessential* qualities.</div><div>Generic algorithms that need to produce a stable ordering of elements will use `<=>`. Those such as `index(of:)` will use `===` to test for identity. Wouldn't that work?</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><span>
><br>
> On Jul 22, 2016, at 6:48 PM, Dave Abrahams via swift-evolution <<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
>>>>><br>
>>>>><br>
>>>>> on Fri Jul 22 2016, Jaden Geller <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
>>>>><br>
>>>>> For floating point, I'd hope that `a === b` if `(a <=> b) == .same`<br>
>>>>> *but not iff*. This is to satisfy IEEE 754: "Comparisons shall<br>
>>>>> ignore the sign of zero (so +0 = −0)".<br>
>>>>><br>
>>>>><br>
>>>>> I don't see why both `(+0) === (-0)` and `(+0) <=> (-0)` can't return<br>
>>>>> `true` and `.same`, respectively. This doesn't break the total<br>
>>>>> ordering of values. `===` doesn't do raw memory comparison. They're<br>
>>>>> "identical", so it ought to return `true`.<br>
>>>>><br>
>>>>><br>
>>>>> It ought to do whatever IEEE-754 specifies that its total ordering test<br>
>>>>> does. That is, IEEE-754 gets to decide whether the difference between<br>
>>>>> +0 and -0 is “essential” to IEEE-754 floating point types, or not.<br>
>>>>><br>
>>>>><br>
>>>>> On Jul 22, 2016, at 6:37 PM, Xiaodi Wu via swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
>>>>><br>
>>>>> On Fri, Jul 22, 2016 at 8:20 PM, Dave Abrahams via swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>> on Fri Jul 22 2016, Daniel Duan <<a href="http://daniel-at-duan.org" target="_blank">daniel-AT-duan.org</a><br>
</span><span>>>>>> <<a href="http://daniel-at-duan.org/" rel="noreferrer" target="_blank">http://daniel-at-duan.org/</a>>> wrote:<br>
>>>>><br>
>>>>> On Jul 22, 2016, at 3:00 PM, Dave Abrahams via swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>><br>
>>>>> on Fri Jul 22 2016, Daniel Duan<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>><br>
>>>>> On Jul 22, 2016, at 11:05 AM, Dave Abrahams via swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>><br>
>>>>> on Thu Jul 21 2016, Duan<br>
>>>>><br>
>>>>><br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>>>><br>
<div><div>>>>>> wrote:<br>
>>>>><br>
>>>>> Great proposal. I want to second that areSame may mislead user to<br>
>>>>> think this is about identity.<br>
>>>>><br>
>>>>> I like areEquivalent() but there may be better names.<br>
>>>>><br>
>>>>><br>
>>>>> It really *is* about identity as I posted in a previous message. But<br>
>>>>> that doesn't change the fact that areEquivalent might be a better name.<br>
>>>>> It's one of the things we considered; it just seemed long for no real<br>
>>>>> benefit.<br>
>>>>><br>
>>>>><br>
>>>>> If the addresses of the arguments aren’t being used, then we don’t<br>
>>>>> consider<br>
>>>>> them part of their *identity*. I can follow this logic. My fear is most<br>
>>>>> users<br>
>>>>> won’t make this leap on their own and get the same initial impression<br>
>>>>> as I did.<br>
>>>>> It's entirely possible this fear is unfounded. Some educated bikesheding<br>
>>>>> wouldn't hurt here IMO :)<br>
>>>>><br>
>>>>><br>
>>>>> Well, it's still a very real question whether we ought to have the<br>
>>>>> additional API surface implied by areSame, or wether we should collapse<br>
>>>>> it with ===.<br>
>>>>><br>
>>>>><br>
>>>>> To spell this out (because I had to think about it for a second): ===<br>
>>>>> will be derived from<br>
>>>>> <=>,<br>
>>>>> but also becomes default implementation for ==, which remains open for<br>
>>>>> customization.<br>
>>>>><br>
>>>>><br>
>>>>> I was imagining roughly this (untested):<br>
>>>>><br>
>>>>> /// Two references are identical if they refer to the same<br>
>>>>> /// instance.<br>
>>>>> ///<br>
>>>>> /// - Note: Classes with a more-refined notion of “identical”<br>
>>>>> /// should conform to `Identifiable` and implement `===`.<br>
>>>>> func ===(lhs: AnyObject, rhs: AnyObject) -> Bool {<br>
>>>>> ObjectIdentifier(lhs) == ObjectIdentifier(rhs)<br>
>>>>> }<br>
>>>>><br>
>>>>> /// Supports testing that two values of `Self` are identical<br>
>>>>> ///<br>
>>>>> /// If `a` and `b` are of type `Self`, `a === b` means that<br>
>>>>> /// `a` and `b` are interchangeable in most code. A conforming<br>
>>>>> /// type can document that specific observable characteristics<br>
>>>>> /// (such as the `capacity` of an `Array`) are inessential and<br>
>>>>> /// thus not to be considered as part of the interchangeability<br>
>>>>> /// guarantee.<br>
>>>>> ///<br>
>>>>> /// - Requires: `===` induces an equivalence relation over<br>
>>>>> /// instances.<br>
>>>>> /// - Note: conforming types will gain an `==` operator that<br>
>>>>> /// forwards to `===`.<br>
>>>>> /// - Note: Types that require domain-specific `==`<br>
>>>>> /// implementations with different semantics (e.g. floating<br>
>>>>> /// point) should define a more-specific overload of `==`,<br>
>>>>> /// which will be used in contexts where the static type is<br>
>>>>> /// known to the compiler.<br>
>>>>> /// - Note: Generic code should usually use `==` to compare<br>
>>>>> /// conforming instances; that will always dispatch to `===`<br>
>>>>> /// and will be unaffected by more specific overloads of<br>
>>>>> /// `==`.<br>
>>>>> protocol Identifiable { // née Equatable name is negotiable<br>
>>>>> func ===(_: Self, _: aSelf) -> Bool<br>
>>>>> }<br>
>>>>><br>
>>>>> /// Default definition of `==` for Identifiable types.<br>
>>>>> func ==<T: Identifiable>(lhs: T, rhs: T) -> Bool {<br>
>>>>> return lhs === rhs<br>
>>>>> }<br>
>>>>><br>
>>>>> /// Conforming types have a default total ordering.<br>
>>>>> ///<br>
>>>>> /// If `a` and `b` are of type `Self`, `a <=> b` means that<br>
>>>>> /// `a` and `b` are interchangeable in most code. A conforming<br>
>>>>> /// type can document that specific observable characteristics<br>
>>>>> /// (such as the `capacity` of an `Array`) are inessential and<br>
>>>>> /// thus not to be considered as part of the interchangeability<br>
>>>>> /// guarantee.<br>
>>>>> ///<br>
>>>>> /// - Requires: `<=>` induces a total ordering over<br>
>>>>> /// instances.<br>
>>>>> /// - Requires: the semantics of `<=>` are consistent with<br>
>>>>> /// those of `===`. That is, `(a <=> b) == .equivalent`<br>
>>>>> /// iff `a === b`.<br>
>>>>><br>
>>>>> For floating point, I'd hope that `a === b` if `(a <=> b) == .same`<br>
>>>>> *but not iff*. This is to satisfy IEEE 754: "Comparisons shall ignore the<br>
>>>>> sign of zero (so +0 = −0)".<br>
>>>>><br>
>>>>> /// - Note: conforming types will gain `<`, `<=`, `>`, and `>=`<br>
>>>>> /// operators defined in terms of `<=>`.<br>
>>>>> /// - Note: Types that require domain-specific `<`, etc.<br>
>>>>> /// implementations with different semantics (e.g. floating<br>
>>>>> /// point) should define more-specific overloads of those<br>
>>>>> /// operators, which will be used in contexts where the<br>
>>>>> /// static type is known to the compiler.<br>
>>>>> /// - Note: Generic code can freely use `<=>` or the traditional<br>
>>>>> /// comparison operators to compare conforming instances;<br>
>>>>> /// the result will always be supplied by `<=>`<br>
>>>>> /// and will be unaffected by more specific overloads of<br>
>>>>> /// the other operators.<br>
>>>>> protocol Comparable : Identifiable {<br>
>>>>> func <=> (lhs: Self, rhs: Self) -> Ordering<br>
>>>>> }<br>
>>>>><br>
>>>>> /// Default implementations of `<`, `<=`, `>`, and `>=`.<br>
>>>>> extension Comparable {<br>
>>>>> static func <(lhs: Self, rhs: Self) -> Bool {<br>
>>>>> return (lhs <=> rhs) == .ascending<br>
>>>>> }<br>
>>>>> static func <=(lhs: Self, rhs: Self) -> Bool {<br>
>>>>> return (rhs <=> lhs) != .ascending<br>
>>>>> }<br>
>>>>> static func >(lhs: Self, rhs: Self) -> Bool {<br>
>>>>> return (lhs <=> rhs) == .descending<br>
>>>>> }<br>
>>>>> static func >=(lhs: Self, rhs: Self) -> Bool {<br>
>>>>> return (rhs <=> lhs) != .descending<br>
>>>>> }<br>
>>>>> }<br>
>>>>><br>
>>>>> I like this idea. If we keep === as a separate thing, now users have 3<br>
>>>>> “opportunities” to define<br>
>>>>> equality. The must be few, if any, use cases for this.<br>
>>>>><br>
>>>>> Would love to see if anyone on the list can give us an example.<br>
>>>>> Otherwise we should make<br>
>>>>> areSame === again™!<br>
>>>>><br>
>>>>><br>
>>>>> Daniel Duan<br>
>>>>> Sent from my iPhone<br>
>>>>><br>
>>>>> On Jul 21, 2016, at 6:32 PM, Robert Widmann via swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</div></div>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>><br>
>>>>> On Jul 21, 2016, at 6:19 PM, Xiaodi Wu<br>
>>>>> <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a><br>
</span>>>>>> <mailto:<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a> <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>>>><br>
<span>>>>>> wrote:<br>
>>>>><br>
>>>>> This is nice. Is `areSame()` being proposed because static `==` is<br>
>>>>> the status quo and you're trying to make the point that `==` in the<br>
>>>>> future need not guarantee the same semantics?<br>
>>>>><br>
>>>>><br>
>>>>> Yep! Equivalence and equality are strictly very different things.<br>
>>>>><br>
>>>>><br>
>>>>> Nit: I think the more common term in stdlib would be<br>
>>>>> `areEquivalent()`. Do you think `same` in that context (independent<br>
>>>>> of the word "ordering") might erroneously suggest identity?<br>
>>>>><br>
>>>>><br>
>>>>> There is room for improvement here. Keep ‘em coming.<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> On Thu, Jul 21, 2016 at 8:11 PM, Robert Widmann via<br>
>>>>> swift-evolution<br>
>>>>> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> wrote:<br>
>>>>> Hello Swift Community,<br>
>>>>><br>
>>>>> Harlan Haskins, Jaden Geller, and I have been working on a<br>
>>>>> proposal to clean up the semantics of ordering relations in the<br>
>>>>> standard library. We have a draft that you can get as a gist.<br>
>>>>> Any feedback you might have about this proposal helps - though<br>
>>>>> please keeps your comments on Swift-Evolution and not on the gist.<br>
>>>>><br>
>>>>> Cheers,<br>
>>>>><br>
>>>>> ~Robert Widmann<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>><br>
>>>>><br>
>>>>> --<br>
>>>>> Dave<br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>>><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>>>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>>><br>
>>>>><br>
>>>>><br>
>>>>> --<br>
>>>>> Dave<br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>><br>
>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>>><br>
>>>>><br>
>>>>><br>
>>>>> --<br>
>>>>> Dave<br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
<span>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
</span>>>>>> <mailto:<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a> <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>><br>
<div><div>>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>> <<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>><br>
>>>>><br>
>>>>> --<br>
>>>>> Dave<br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> _______________________________________________<br>
>>>>> swift-evolution mailing list<br>
>>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
>>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>>><br>
>>>>><br>
>>>> _______________________________________________<br>
>>>> swift-evolution mailing list<br>
>>>> <a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
>>>> <a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br>
>>>><br>
>>>><br>
>>><br>
>><br>
>><br>
<br>
</div></div><span><font color="#888888">--<br>
Dave<br>
</font></span></blockquote></div><br></div></div>
</div></blockquote></div></div></div></blockquote></div><br></div></div>