I quite like this variation, so I’m a +1 for that.
However, I think this would be greatly helped if we could define protocol
generics more like type generics like so:
protocol Foo<Element> { … }
func anyStringFoo(lhs:Foo<String>) { … }
But yeah, for the more complicated cases, it makes a lot of sense to relocate
the where clause away from the main signature. I’d maybe still allow
declarations of type though like-so:
func anyCommonElements<T:SequenceType, U:SequenceType>(lhs:T, _ rhs:U)
-> Bool
where T.Generator.Element:Equatable, T.Generator.Element ==
U.Generator.Element
Perhaps allowing us the choice of doing it this way at least.
> On 6 Apr 2016, at 19:35, Pyry Jahkola via swift-evolution
> <[email protected]> wrote:
>
>> On 06 Apr 2016, at 21:30, Developer via swift-evolution
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>> If you've ever gotten to the point where you have a sufficiently generic
>> interface to a thing and you need to constrain it, possibly in an extension,
>> maybe for a generic free function or operator, you know what a pain the
>> syntax can be for these kinds of operations.
>
> +1 already!
>
>> Or, if you're feeling ambitious, even
>>
>> func anyCommonElements <T, U>
>> where T : SequenceType, U : SequenceType,
>> T.Generator.Element: Equatable, T.Generator.Element == U.Generator.Element
>> (lhs: T, _ rhs: U) -> Bool
>
> I would actually move them as far as after everything else, and right before
> the definition body. For the above function that would mean:
>
> func anyCommonElements<T, U>(lhs: T, _ rhs: U) -> Bool
> where T : SequenceType,
> U : SequenceType,
> T.Generator.Element: Equatable,
> T.Generator.Element == U.Generator.Element
> {
> ...
> }
>
> That would make the definition look closer to what the call site looks like.
>
> The same would work for generic types too:
>
> public struct Dictionary<Key, Value>
> where Key : Hashable
> {
> ...
> }
>
> — Pyry
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