[swift-evolution] Proposal: Contiguous Variables (A.K.A. Fixed Sized Array Type)

Dave Abrahams dabrahams at apple.com
Fri Jan 29 15:11:21 CST 2016

on Thu Jan 28 2016, Chris Lattner <swift-evolution at swift.org> wrote:

>> On Jan 28, 2016, at 9:41 PM, Félix Cloutier <felixcca at yahoo.ca> wrote:
>> I think that (4 x Int) needs to be syntax sugar for (Int, Int, Int,
>> Int). Not having them the same would introduce awkward cases into
>> the language.
> Agreed.  This means that:
>    let values: (4 x Int)(repeatedValue: 0) // Is this possible?
> will not be possible.

I think this avenue leaves some really crucial use-cases on the table,
e.g. implementing bounded-size dynamically-growable arrays.  There
should, at the very least, be a way to declare an array of uninitialized
suitably-aligned storage for any type.  And I think we'd also need
non-type generic parameters to complete the picture.

>> Because of that, I also think that forcing people to use the
>> subscript would have some awkward consequences. What if I have a
>> func<T, U> that uses a (T, U) tuple and both T and U happen to be
>> the same type?
> I don’t understand this concern.
>> So I think that tuples whose elements all have the same type should
>> get a subscript but shouldn't lose direct field access.
> Agreed.
> -Chris
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