> Am 27.05.2016 um 10:30 schrieb Austin Zheng <austinzh...@gmail.com>: > > Thank you for all your great feedback! > > Let me try rephrasing what I said, because it wasn't very clear. Apologies. > > NSView is not an existential, like you said. > > Any<...> syntax is, as far as we've seen, always used for existential types. > > "Any<NSView>" *looks* like an existential because it has the "Any<...>" > syntax, but if it's a synonym for just "NSView" then it actually isn't an > existential. > > So "Any<NSView>" isn't an existential, but it looks like one. This is > something I think would be confusing to a lot of people, and also redundant: > there is no reason as far as I know to ever write Any<SomeClass> when you > could just write SomeClass, so by banning the confusing form we don't lose > any expressive power.
Ah, ok! So `Any<NSView>` is just the same as `NSView`. That’s my understanding as well :-) But this does not apply only to classes: `Any<CustomStringConvertible>` is just the same as `CustomStringConvertible`, too, because `CustomStringConvertible` does not have associated types or self type requirements (it is *not* an existential in Wikipedia’s sense). Banning `Any<Foo>` where `Foo` does not have associated types or self type requirements would be the right thing to do, I think, regardless whether `Foo` is a class or a protocol. This would make it clear that `Any<Foo>` is a *real* existential. -Thorsten > > Hope that helps, > Austin > >> On May 27, 2016, at 1:24 AM, Thorsten Seitz <tseit...@icloud.com >> <mailto:tseit...@icloud.com>> wrote: >> >>> >>> Am 26.05.2016 um 22:44 schrieb Austin Zheng via swift-evolution >>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>>: >>> >>> (inline) >>> >>> On Thu, May 26, 2016 at 12:22 PM, David Hart <da...@hartbit.com >>> <mailto:da...@hartbit.com>> wrote: >>> Hi Austin, >>> >>> I never had te occasion to say thanks for the work you have put in this >>> proposal, so thanks! I’m really looking forward to be able to have some >>> form of it accepted and implemented in Swift. >>> >>> Thank you! I just hope a proposal like this one ends up being good enough >>> that it means less work for the core team, not more... >>> >>> >>> Here are a few comments: >>> >>> 1) Why would Any<> and Any<NSView> be illegal? What error messages would >>> they generate? Why not make them simply synonymous to Any, and NSView, the >>> same way protocol<> currently behaves? >>> >>> "Any<>" being illegal is a syntactic battle that is being fought over in a >>> different thread; I'm not personally invested one way or another. (We might >>> not even adopt "Any" syntax specifically; Joe Groff has ideas for a >>> different syntax that doesn't use the brackets.) >>> >>> "Any<NSView>" is an existential, and "NSView" isn't. Existentials' >>> metatypes are different from the metatypes of concrete types, and the ways >>> they can be used with generics is different as well. My opinion is that >>> Any<...> signifies an existential, and allowing the use of "Any<SomeClass>" >>> as a concrete type would just confuse people even more. >> >> >> This is something where I still have a problem understanding what an >> existential is in the Swift sense. In the "normal“ sense (as defined in >> Wikipedia or Haskell) NSView cannot be an existential because it has no >> unbound associated types. It cannot be just made an existential either. How >> would that work? >> >> So, what is the meaning of `Any<NSView>` being an existential? How is that >> type different from the type `NSView`? >> >> -Thorsten >
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
