[swift-evolution] [Pitch] New Version of Array Proposal

Daryle Walker darylew at mac.com
Sun Jul 23 22:05:05 CDT 2017

> On Jul 23, 2017, at 2:07 PM, Nevin Brackett-Rozinsky via swift-evolution <swift-evolution at swift.org> wrote:
> I think fixed-size arrays should be a nominal type like any other. They should be able to have methods, conform to protocols, be extended with new behavior, and generally present a user-experience similar to what arrays already have. In particular, they should conform to Collection and to ExpressibleByArrayLiteral.

Nominal types have to be completely initialized in their initializer, and I don’t think that should change. But we want to allow arrays to start off uninitialized, instead of a blanket initialization that would be paved over by the real initial data. That’s one reason FSAs are compound types. Another reason is that they’re kind-of low level, like tuples.

As I said in some other responses, the solution to slapping methods/protocols/other-new-interfaces to compound types is to make a strong type-alias of that type and add your interface there. (Once we have strong type-aliases, of course.)

I have fixed-size arrays to be compound types because 

> If we are going to use semicolons at all, it should be to demarcate the rows of a 2-dimensional array, as that will be one of the most common use-cases:
> let identity3x3: [Int(3, 3)] = [1, 0, 0;
>                                 0, 1, 0;
>                                 0, 0, 1]

That doesn’t seem scalable to higher dimensions.

Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT mac DOT com 

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