> Am 27.05.2016 um 20:47 schrieb Matthew Johnson via swift-evolution
> <swift-evolution@swift.org>:
>
>
>> On May 27, 2016, at 12:05 PM, Charles Srstka via swift-evolution
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>
>>> On May 27, 2016, at 9:31 AM, plx via swift-evolution
>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>
>>> For the Sequence/Collection it’s a lot of work for IMHO a rather minor
>>> convenience, but for more-complex type associated-type relationships it
>>> could start to pay its own way.
>>
>> Is it really that minor, though? For something so commonly encountered as
>> methods that take sequences/collections, this:
>>
>> func doSomething(foos: [Foo], bars: [Bar], bazzes: [Baz])
>>
>> is not only a whole lot easier to type, but is worlds clearer to read than:
>>
>> func doSomething<S: SequenceType, T: SequenceType, U: SequenceType where
>> S.Generator.Element == Foo, T.Generator.Element == Bar, U.Generator.Element
>> == Baz>(foos: S, bars: T, bazzes: U)
>>
>> Not only is the latter line intimidating to look at as is, but it separates
>> the contained type from the parameters themselves. Given how unwieldy this
>> second form is, it seems almost certain that the former line will be used
>> more frequently in the real world.
>
> When generalized existentials are introduced (Austin Zheng has a proposal for
> this) you will be able to do this (assuming we switch to the `&` syntax:
>
> typealias SequenceOf<T> = Sequence where .Element == T
>
> func doSomething(foos: SequenceOf<Foo>, bars: SequenceOf<Bar>, bazzes:
> SequenceOf<Baz>)
That’s a really nice solution, which gets even nicer with plx suggestion of
putting the typealias within the protocol like this:
protocol Sequence {
typealias of<E> = S: Self where .Element == E
}
-Thorsten
>
> It’s still slightly more verbose than the array shorthand, but it’s a far cry
> from what you have to do with generics today.
>
> If you wanted it to be generic you could write it as:
>
> func doSomething<S: SequenceOf<Foo>, T: SequenceOf<Bar>,
> SequenceOf<Baz>(foos: S, bars: T, bazzes: U)
>
>>
>> Charles
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution@swift.org <mailto: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
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
