[swift-evolution] [Draft][Proposal] Formalized Ordering

Brent Royal-Gordon brent at architechies.com
Fri Jul 22 21:00:16 CDT 2016

> On Jul 22, 2016, at 4:55 PM, Daniel Duan via swift-evolution <swift-evolution at swift.org> wrote:
>> Well, it's still a very real question whether we ought to have the
>> additional API surface implied by areSame, or wether we should collapse
>> it with ===.
> To spell this out (because I had to think about it for a second): === will be derived from
> <=>, but also becomes default implementation for ==, which remains open for customization.
> I like this idea. If we keep === as a separate thing, now users have 3 “opportunities” to define
> equality. The must be few, if any, use cases for this.
> Would love to see if anyone on the list can give us an example. Otherwise we should make
> areSame === again™!

If `===` is the new `areSame`, and `Hashable` is based on `===`, wouldn't that mean that objects could only be hashed (and thus, be looked up in Dictionary and Set) by identity? So, for instance, code like this:

	var set = Set<NSString>()

Would print "2"? Or worse, might print "1" or "2" depending on the details of how Swift generates literals and Foundation implements short strings?

Am I the only one who thinks that's a problem?

Brent Royal-Gordon

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