SE-0425: 128-bit Integer Types

[tera]

@beccadax

if [U]Int128 had existed when SE-0166 was written, we would have included these methods

@beccadax

(for instance, Swift.Duration would probably have used Int128 if it had been available)

Maybe not:

@lorentey

@wadetregaskis

If Int128 existed at the time Duration was defined, would it have been defined differently? e.g. to just use an Int128, or even to just be an Int128?

No, I don't think so! The alignment of Duration was very intentionally chosen to be the same as Int64 everywhere (usually 8, except i386, where presumably it's 4).

I do agree it's worth making Int128 Codable, just the proposed default method of doing so (a pair of 64bit integers) concerns me.