Sent from my iPad
> On May 28, 2016, at 12:40 PM, Thorsten Seitz <tseit...@icloud.com> wrote:
>
>
>>> 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> wrote:
>>>>
>>>> On May 27, 2016, at 9:31 AM, plx via swift-evolution
>>>> <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
> }
That is very nice!
>
> -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
>>>
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>>
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>
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