That doesn't follow for me at all. The structure formed by Instants and Durations is an affine space <https://en.wikipedia.org/wiki/Affine_space#Definition>, with instants the points and durations the vectors. (An affine space is a vector space without a distinguished origin, which of course Instants don't have.) It is 100% standard to use the minus sign for the operation "point - point = vector," even when "point + point" is not defined, and to use all the other standard idioms for subtraction; the Wikipedia article uses "subtraction" and "difference" ubiquitously.
Personally, I'd be willing to live with a different name for the operation, but consider "users keep getting it wrong" a strong enough argument all by itself for a version with the swapped argument order; it's not obvious to me that another API with the same argument order adds enough value over Duration.between to bother with. On Thu, May 2, 2024 at 10:04 AM Stephen Colebourne <scolebou...@joda.org> wrote: > On Thu, 2 May 2024 at 15:58, Kurt Alfred Kluever <k...@google.com> wrote: > > instant − instant = duration // what we're discussing > > instant + duration = instant // satisfied by instant.plus(duration) > > instant - duration = instant // satisfied by instant.minus(duration) > > duration + duration = duration // satisfied by duration.plus(duration) > > duration - duration = duration // satisfied by duration.minus(duration) > > duration × real number = duration // satisfied by > duration.multipliedBy(long) > > duration ÷ real number = duration // satisfied by > duration.dividedBy(long) > > > > All but the first operation have very clear translations from conceptual > model to code. I'm hoping we can achieve the same clarity for instant - > instant by using the obvious name: instant.minus(instant) > > But you can't have > instant + instant = ??? > It doesn't make sense. > > This is at the heart of why minus isn't right in this case. > Stephen > -- Louis Wasserman (he/they)
