This comparison shouldn't need tuple conformance to Equatable, right?

[CTMacUser (Daryle Walker)]

@anon9791410

I think you're making this too complex by trying to make (nil, nil) actually mean the same as a wrapping nil . Instead, how about this?

[Elide a much more complex workaround, which also changes the interface.]

I don't want to make that equivalence; I just wanted to compare both members to nil at once. It it's not worth it, so I just did:

@erikstrottmann

But it might be simpler to just compare the elements to nil one-by-one in elementsEqual2 :

let delta = try firstDelta(against: other, by: areEquivalent)
return delta.0 == nil && delta.1 == nil

I have two Optionals within a non-Optional tuple because the four states have distinct user-level meanings. Neither being nil means each sequence has at least one element after a common prefix. Only the first as nil means that the first sequence is a prefix of the second. Vice-versa goes when only the second is nil. The sequences are identical when both returns are nil. What is your fifth state (making the entire tuple nil) supposed to mean?