Special Case Protocol Conformance: Long-term Tradeoffs for Near-term Conformance

[Jens]

@skaller

In particular, consider that a tuple is a weak type with no particular meaning. two different users may have a different concept of say ordering. Just consider a pair of doubles representing a complex number .. which has no order.

I asked about that in the pitch thread:

@Jens

Is there really an obvious (and mandatory, non-customizable) Comparable -conformance that would make sense for eg these:

let person = (firstName: "Ada", lastName: "Lovelace", birthDate: Date(/*...*/))
let coordinate = (latitude: 40.689263, longitude: -74.044505)
let dmy = (day: 30, month: 1, year: 2020)
let ymd = (year: 2020, month: 1, day: 30)  

?

Yes—lexicographic comparison from left to right. SE-0015 already added overloads of < and friends to implement precisely this behavior for tuples of 1-6 elements; they just aren't formally modeled as a Comparable conformance.