[swift-evolution] [swift-dev] Re-pitch: Deriving collections of enum cases

Karl Wagner razielim at gmail.com
Sat Dec 9 14:45:07 CST 2017


Personally, I think this dovetails quite nicely with the ‘random’ discussion. Enums are just one kind of type with a finite set of values; Int and Bool also fit that description, as may many structs and even classes.

Having a general way to express that would be quite nice, IMO.

- Karl

> On 9. Dec 2017, at 06:19, Step Christopher via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Has this stalled out again? I would like to help with the proposal and even attempt implementation. 
> 
> I also need to catch up on the resilient discussion regarding enum case ordering. 
> 
> On Nov 14, 2017, at 10:50 PM, Jacob Bandes-Storch via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> 
>> 
>> Jacob Bandes-Storch
>> 
>> On Tue, Nov 14, 2017 at 9:06 PM, Brent Royal-Gordon <brent at architechies.com <mailto:brent at architechies.com>> wrote:
>>> On Nov 14, 2017, at 5:21 PM, Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>> wrote:
>>> 
>>> 1. It must be possible to easily access the count of values, and to access any particular value using contiguous `Int` indices. This could be achieved either by directly accessing elements in the list of values through an Int subscript, or by constructing an Array from the list of values.
>>> 
>>> 2. It must be possible to control the order of values in the list of values, either by using source order or through some other simple, straightforward mechanism.
>>>  
>>> OK, first of all, nowhere in the proposal text are these requirements stated as part of the use case. You're free to put forward new use cases, but here I am trying to design the most elegant way to fulfill a stated need and you're telling me that it's something other than what's written.
>> 
>> Honestly, re-reading the proposal, it never cites a fully-formed use case. Instead, it cites several blog posts, Stack Overflow questions, and small code samples without digging in to the underlying reasons why developers are doing what they're doing. Most of the people discussing it so far seem to have had a tacit understanding that we wanted roughly Array-like access, but we haven't explicitly dug into which properties of an Array are important.
>> 
>> (If anyone involved feels like they had a different understanding of the use case, please speak up.)
>> 
>> I think this is a place where the proposal can be improved, and I'm willing to do some writing to improve it.
>> 
>> For the record, I would be happy to add co-authors (or even relinquish authorship entirely—I don't really care whose name is on this, it just needs to happen!) if you or anyone else has improved wording, motivation, justification, etc. to contribute.
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