[swift-evolution] [Proposal] Set literal and Set type syntax

[Maximilian Hünenberger]

What about the mathematical Set notation?:

let numbers = {3, 1, 4, 1, 5, 9, 2, 6, 5, 3}

But this is highly ambiguous in those cases:
let numbers = {} // closure ()->()
let numbers = {3} // closure ()->Int

So a type annotation is still needed at least for empty Sets and single element ones. There could be also some difficulties while parsing the swift file.

As some others have said I'm not sure whether such additional syntax pays off.

- Maximilian

> Am 19.01.2016 um 23:00 schrieb T.J. Usiyan via swift-evolution <swift-evolution at swift.org>:
> 
> I agree that the probably isn't a better story for literals and Sets and that I wish that there were a better story.
> 
> The best that I can think of is some sort of flag outside of the Array literal, for instance, #["A", "B", "C"] or just using keys that people aren't already accustomed to like option-'\' and option-shift-'\'.  «"A", "B", "C"]»
> 
> 
> TJ
> 
>> On Tue, Jan 19, 2016 at 4:55 PM, Greg Parker via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>>>> On Jan 18, 2016, at 2:55 PM, Howard Lovatt via swift-evolution <swift-evolution at swift.org> wrote:
>>>> 
>>>>> On Tuesday, 19 January 2016, Jack Lawrence <jackl at apple.com> wrote:
>>>>> 
>>>>> On Jan 18, 2016, at 2:50 PM, Liam Butler-Lawrence via swift-evolution <swift-evolution at swift.org> wrote:
>>>>> 
>>>>> Set("a", "b", "c”) doesn’t compile. It currently has to be  Set(arrayLiteral: "a", "b", "c”). That said, I’d be satisfied with removing the external parameter name “arrayLiteral”. Not only is it unnecessary, but it’s confusing too: variadic parameters are not the same as an Array.
>>>> 
>>>> init(arrayLiteral:) is there to satisfy ArrayLiteralConvertible. Set([“a”, “b”, “c”]) works just fine.
>>> 
>> 
>>> Sure, but you could add another overload without the label.
>> 
>> 
>> Only if you break existing code. Consider this expression:
>> 
>>     Set(["a", "b"])
>> 
>> Is this
>> 1. a Set<String> with two elements "a" and "b"
>> 2. a Set<Array<String>> with one element ["a", "b"]
>> 
>> Currently it means #1. You could change it to mean #2, but that breaks existing code that expects #1. You could try to overload the no-name initializer, but that will be confusing to humans in some cases.
>> 
>> 
>> -- 
>> Greg Parker     gparker at apple.com     Runtime Wrangler
>> 
>> 
>> 
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