[swift-evolution] [swift-evolution-announce] [Review] SE-0089: Replace protocol<P1, P2> syntax with Any<P1, P2>

Fri May 27 08:18:02 CDT 2016

Personally I think `&` is more lightweight (and it is established in other languages like Ceylon and Typescript) and `where` is more expressive (and established in Swift for introducing constraints), so I would stay with these.

-Thorsten

> Am 27.05.2016 um 14:34 schrieb Vladimir.S <svabox at gmail.com>:
> 
> Btw, in case we have `where` keyword in syntax related to types/protocols (when defining constrains. and not some symbol like '>>'.. don't know, for example), why we can't have 'and' keyword also when discuss the syntax of type/protocol conjunction?
> I.e.
> 
> let x: P and Q
> let x: P and Q where P.T == Q.T
> let x: P and Q and R
> 
> or, for consistency, as I understand it, we should have
> let x: P & Q >> P.T == Q.T
> 
> On 27.05.2016 11:55, Thorsten Seitz via swift-evolution wrote:
>> We could just write
>> 
>> let x: P & Q
>> instead of
>> let x: Any<P, Q>
>> 
>> let x: Collection where .Element: P
>> instead of
>> let x: Any<Collection where .Element: P>
>> 
>> let x: P & Q where P.T == Q.T
>> instead of
>> let x: Any<P, Q where P.T == Q.T>
>> 
>> let x: P & Q & R
>> instead of
>> let x: Any<P, Q, R>
>> 
>> let x: Collection
>> instead of
>> let x: Any<Collection>
>> 
>> 
>> This would avoid the confusion of Any<T1, T2> being something completely
>> different than a generic type (i.e. order of T1, T2 does not matter whereas
>> for generic types it is essential).
>> 
>> 
>> -Thorsten
>> 
>> 
>> 
>>> Am 26.05.2016 um 20:11 schrieb Adrian Zubarev via swift-evolution
>>> <swift-evolution at swift.org <mailto:swift-evolution at swift.org> <mailto:swift-evolution at swift.org <mailto:swift-evolution at swift.org>>>:
>>> 
>>> Something like |type<…>| was considered at the very start of the whole
>>> discussion (in this thread
>>> <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160502/016523.html <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160502/016523.html>>),
>>> but it does not solve the meaning of an existential type and also might
>>> lead to even more confusion.
>>> 
>>> From my perspective I wouldn’t use parentheses here because it looks more
>>> like an init without any label |Type.init(…)| or |Type(…)|. I could live
>>> with |Any[…]| but this doesn’t look shiny and Swifty to me. Thats only my
>>> personal view. ;)
>>> 
>>> 
>>> 
>>> 
>>> --
>>> Adrian Zubarev
>>> Sent with Airmail
>>> 
>>> Am 26. Mai 2016 bei 19:48:04, Vladimir.S via swift-evolution
>>> (swift-evolution at swift.org <mailto:swift-evolution at swift.org> <mailto:swift-evolution at swift.org <mailto:swift-evolution at swift.org>>) schrieb:
>>> 
>>>> Don't think {} is better here, as they also have "established meaning in
>>>> Swift today".
>>>> 
>>>> How about just Type(P1 & P2 | P3) - as IMO we can think of such
>>>> construction as "creation" of new type and `P1 & P2 | P3` could be treated
>>>> as parameters to initializer.
>>>> 
>>>> func f(t: Type(P1 & P2 | P3)) {..}
>>>> 
>>>> 
>>>> On 26.05.2016 20:32, L. Mihalkovic via swift-evolution wrote:
>>>> > How about something like Type{P1 & P2 | P3} the point being that "<...>" has an established meaning in Swift today which is not what is expressed in the "<P1,P2,P3>" contained inside Any<P1, P2,P3>.
>>>> >
>>>> >> On May 26, 2016, at 7:11 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org> <mailto:swift-evolution at swift.org <mailto:swift-evolution at swift.org>>> wrote:
>>>> >>
>>>> >>
>>>> >>> on Thu May 26 2016, Adrian Zubarev <swift-evolution at swift.org <mailto:swift-evolution at swift.org> <mailto:swift-evolution at swift.org <mailto:swift-evolution at swift.org>>> wrote:
>>>> >>>
>>>> >>> There is great feedback going on here. I'd like to consider a few things here:
>>>> >>>
>>>> >>> * What if we name the whole thing `Existential<>` to sort out all
>>>> >>> confusion?
>>>> >>
>>>> >> Some of us believe that “existential” is way too theoretical a word to
>>>> >> force into the official lexicon of Swift. I think “Any<...>” is much
>>>> >> more conceptually accessible.
>>>> >>
>>>> >>>
>>>> >>> This would allow `typealias Any = Existential<>`. * Should
>>>> >>> `protocol A: Any<class>` replace `protocol A: class`? Or at least
>>>> >>> deprecate it. * Do we need `typealias AnyClass = Any<class>` or do we
>>>> >>> want to use any class requirement existential directly? If second, we
>>>> >>> will need to allow direct existential usage on protocols (right now we
>>>> >>> only can use typealiases as a worksround).
>>>> >>
>>>> >> --
>>>> >> Dave
>>>> >>
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