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

[Thorsten Seitz]

> Am 16.10.2017 um 00:46 schrieb Xiaodi Wu <xiaodi.wu at gmail.com>:
> 
> On Sun, Oct 15, 2017 at 2:39 PM, Kevin Nattinger <swift at nattinger.net> wrote:
>>> […]
>>> Swift's Sequence protocol does not require the order of iteration to "convey any meaning"; it doesn't even require it to be deterministic.
>>> 
>> 
>> And that’s EXACTLY why none of the functions on Sequence should rely on the order conveying meaning.  `ElementsEqual` (for example) DOES rely on the order of iteration conveying a meaning not required by the protocol, and renaming it `lexicographicallyEquals` does not change that fact. Either Sequence needs to require a meaningful order or `elementsEqual` should be moved to a protocol that does.
> 
> What's your basis for saying that `elementsEqual` requires orders of iteration that "convey a meaning"? It merely answers the question of whether iterating over `a` is substitutable for iterating over `b`, a question applicable to instances of any type which offers iterated access.
> 

As Set has no intrinsic order of elements just imagine it was implemented to have each iterator created on it to iterate in a random order. This would satisfy the Sequence protocol (or rather its Iterable part hich should be split off) and clearly show that the order is meaningless for Sets.

-Thorsten
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20171016/6be043e8/attachment.html>