[swift-evolution] [Pitch] Moving where Clauses Out Of Parameter Lists
Developer
devteam.codafi at gmail.com
Wed Apr 6 14:35:42 CDT 2016
Even better. +1.
~Robert Widmann
2016/04/06 14:35、Pyry Jahkola via swift-evolution <swift-evolution at swift.org> のメッセージ:
>> On 06 Apr 2016, at 21:30, Developer via swift-evolution <swift-evolution at swift.org> 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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