# [swift-evolution] [Draft] Rename Sequence.elementsEqual

Manolo van Ee manolo.vanee at gmail.com
Tue Oct 17 15:47:05 CDT 2017

```If that’s an option, that could help.

To me it feels like there might be something that could be fixed in the
design. However, I’m not aware of all the things that were considered when
creating the current design, and how much impact it will have to change it,
so I can’t say too much about it and will leave it to more knowledgeable
people to have an opinion on that.

Regards,
/Manolo

On Tue, 17 Oct 2017 at 22:27, Michael Ilseman <milseman at apple.com> wrote:

> (I saw this after I sent my reply to Benjamin G). We can also deprecate it
> or warn when the type is concretely known to be Set. Not a total solution,
> but it’s nice to catch some bugs.
>
>
> On Oct 17, 2017, at 1:21 PM, Manolo van Ee <manolo.vanee at gmail.com> wrote:
>
>
> On Tue, 17 Oct 2017 at 21:00, Jonathan Hull via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>>
>> On Oct 17, 2017, at 11:47 AM, Michael Ilseman via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>> `==` conveys substitutability of the two Sequences. This does not
>> necessarily entail anything about their elements, how those elements are
>> ordered, etc., it just means two Sequences are substitutable.
>> `elementsEqual` means that the two Sequences produce substitutable
>> elements. These are different concepts and both are independently useful.
>>
>>
>> I agree that ‘==‘ conveys substitutability.  Here is the issue:
>>
>> let a = Set([1,2,3,4,5])
>> let b = Set([5,4,3,2,1])
>>
>> a == b //True, they are substitutable
>>
>> [1,2,3,4,5].elementsEqual(a) //True
>> [1,2,3,4,5].elementsEqual(b) //False… I guess they weren’t actually
>> substitutable after all
>>
>>
>> Thanks,
>> Jon
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>
> I read along with most of the thread and like to add one thing. Maybe it’s
> not the right way to look at things, but I see protocol extensions as being
> part of any type that conforms to the protocol. As it is now, code
> completion on a Set will present me with the elementsEqual function, which
> in my view is misleading, since it cannot be used in any useful way with a
> Set.
>
> By renaming elementsEqual we might be able to make it less misleading, but
> it will always be a useless function that is part of the Set namespace (or
> Dictionary for that matter).
>
> I don’t know what the best solution would be, but to me it feels like
> distinguishing between Iterable and Sequence, or Ordered and Unordered
> makes sense, and it might be good to at least investigate what the impact
> would be.
>
> Regards,
> /Manolo
>
>
>
>
>
>
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