[swift-users] is this a defect in equatable for swift tuples?

[Henrique Valcanaia]

If you take a look on the equal operator for tuples, you will see that both elements of the tuple must conform to Equatable.

public func ==<A, B>(lhs: (A, B), rhs: (A, B)) -> Bool where A : Equatable, B : Equatable

Your SomeClass doesn’t conforme to Equatable so it doesn’t work. If you just add the conformance it’ll work.

class SomeClass { }

extension SomeClass: Equatable {
    static func ==(_ lhs: SomeClass, _ rhs: SomeClass) -> Bool {
        return lhs === rhs
    }
}

let c1 = SomeClass()
let t1 = ("abc", c1)
let t2 = ("abc", c1)
t1 == t2 // legal
// true


Regards,
Henrique Valcanaia
Co-founder | iOS Engineer @ Darkshine.io <http://darkshine.io/>
Computer Engineering undergraduate student @ Inf UFRGS
http://bit.ly/valcanaia <http://bit.ly/valcanaia>
> On 9 Jul 2017, at 12:11, David Baraff via swift-users <swift-users at swift.org> wrote:
> 
> Given 2-tuples of type (T1, T2), you should be able to invoke the == operator if you could on both types T1 and T2, right?  i.e.
> 
> (“abc”, 3) == (“abc”, 4)	// legal
> 
> but:
> 
> class SomeClass {
>     static public func ==(_ lhs:SomeClass, _ rhs:SomeClass) -> Bool {
>         return lhs === rhs
>     }
> }
> 
> let c1 = SomeClass()
> let c2 = SomeClass()
> 
> let t1 = ("abc", c1)
> let t2 = ("abc", c2)
> 
> c1 == c2		// legal
> t1 == t2		// illegal
> 
> 
> 
> 
> Why is t1 == t2 not legal given that c1 == c2 IS legal?
> 
> 
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170709/92ca91a9/attachment.html>