[swift-evolution] Checking in; more thoughts on arrays and variadic generics

Slava Pestov spestov at apple.com
Fri Jan 27 15:25:44 CST 2017

> On Jan 27, 2017, at 11:44 AM, Karl Wagner via swift-evolution <swift-evolution at swift.org> wrote:
> So, 2 quick points:
> 1) I have often wanted a shorthand for expressing long tuples; I definitely think that’s something worth bike-shedding, e.g. - (String * 4, Int32 * 4) or something

Why not define a struct, or a tuple consisting of two arrays?

> 2) Having a special non-growing array type which is called “array” and separate from Array<T> is not such a good idea IMO. I would rather allow tuples to conform to protocols (see: https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types <https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types>).
> If tuples could conform to protocols, we could say “any tuple of homogenous elements is a Collection”. There would be benefits for the standard library, too - EmptyCollection<T> would disappear, replaced with the empty tuple (),

This sounds too clever.

> as would CollectionOfOne<T>, to be replaced by a single-element tuple (T).

For what it’s worth, Swift doesn’t have single-element tuples. (T) is just sugar for the type T itself.

> We would also be able to remove our limited-arity == overloads in favour of actual, honest-to-goodness Equatable conformance.

I like this idea though.

> - Karl
>  <https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types>_______________________________________________
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