Hi Thiago, On 03.11.22 16:17, Thiago Macieira wrote: > the devil will be in the details because of QT_REMOVED_SINCE.
What, specifically, are you thinking about here? For the sketched approach to work, no new relational operator must be exported, because we need to keep BC between C++17 and C++20 builds. If existing ones are, we'll need to QT_REMOVED_SINCE them. Where's the problem? > For some classes, we could postpone changing anything until C++20 is required. You lost me there. Why do you think so? Because of the sentence above? Requiring C++20 won't be a BC break, so we'd still have all the old exported relational operators to QT_REMOVED_SINCE. > Meanwhile, we have qcompare.h. Here, too, I feel lost. I'm struggling to see what a NIH std::partial_ordering w/o the weak and strong counterparts and w/o op<=> language support could achieve, except another vocabulary type mismatch. Can you elaborate? Meanwhile, in a Jira comment, Eddy discovered a potential problem with partial_ordering::unordered: we have a lot of types that have std::optional folded into them (isNull/isValid) and, if they're ordered, they need to have decided on a total order, ie. incl. for invalid/null ones (QDateTime sorts invalid before valid e.g.). These types' op<=> could now return unordered for invalid values, but that would change the semantics of the op< derived from it vis a vis the existing op<. I'm also fearful that Qt might be the only library that makes such widespread use of partial_ordering::unordered, because it's the only library that bakes optional semantics into so many of its types. So, for new classes, by all means, use partial_ordering, but for existing types, I'd err on the side of caution and keep the total ordering for now and see how the greater C++ ecosystem's support for partial_ordering::unordered evolves. After all, unordered just means NaN semantics, and I've never heard of someone that likes that behaviour: NaN == NaN is false NaN != NaN is false NaN < NaN is false ... Thanks, Marc _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development