[libcxx-commits] [PATCH] D107584: [libc++][modularisation] Split up <concepts> into granular headers.

[Christopher Di Bella via Phabricator via libcxx-commits]

cjdb added a comment.

In D107584#2936914 <https://reviews.llvm.org/D107584#2936914>, @Quuxplusone wrote:

> @ldionne or @cjdb, any final comments on this splitting-up?

Yes. This isn't "obviously correct" and is missing maintainer/two co-approver LGTMs, and there's an unresolved discussion.



================
Comment at: libcxx/include/__concepts/invocable.h:34-35
+
+template<class _Fn, class... _Args>
+concept regular_invocable = invocable<_Fn, _Args...>;
+
----------------
Quuxplusone wrote:
> cjdb wrote:
> > Quuxplusone wrote:
> > > cjdb wrote:
> > > > Quuxplusone wrote:
> > > > > cjdb wrote:
> > > > > > Quuxplusone wrote:
> > > > > > > cjdb wrote:
> > > > > > > > It's not immediately clear that `regular_invocable` lives in `invocable.h`. Please either:
> > > > > > > > 
> > > > > > > > * split the file up further
> > > > > > > > * consolidate with the other callable concepts and call the header `callable.h`
> > > > > > > > 
> > > > > > > > I'm indifferent to the chosen approach, but please be consistent in the approach you choose.
> > > > > > > I prefer not to split `invocable` from `regular_invocable`, because they are (as far as libc++ is concerned) equivalent.
> > > > > > > However, it's good to split this concept from `predicate` and `relation` (and the other concepts equivalent to `relation`) because //this// file doesn't depend on `__boolean_testable` but //those// concepts do.
> > > > > > :shrug: I guess the same argument that I made for `equality_comparable.h` vs `equality_comparable_with.h` could be made here re not splitting further. Though, I'm not sure why you're opposed to `__boolean_testable` being in this header. Ditto for `object.h`, but we should keep the conversation in one place.
> > > > > `__boolean_testable` is an ancestor of both `equality_comparable` and `predicate`.
> > > > Yes, but `__boolean_testable` has its own header. I'm trying to work out why you're opposed to combining the all the callables into a single header, and you pointed at `__boolean_testable`.
> > > I must not understand what you're asking, because it //seems// like this is really basic.
> > > My initial PR had:
> > > `invocable` and `regular_invocable` go in `invocable.h`, which does not include `boolean_testable.h`.
> > > `predicate` and `relation` and `equivalence_relation` and so on go in `relation.h`, which does include `boolean_testable.h`.
> > > 
> > > My current PR splits `predicate` into `predicate.h`, purely on the basis of name-spelling, because you asked for it.
> > > I prefer not to split `invocable` from `regular_invocable`, because they are (as far as libc++ is concerned) equivalent.
> > > However, it's good to split this concept from `predicate` and `relation` (and the other concepts equivalent to `relation`) because //this// file doesn't depend on `__boolean_testable` but //those// concepts do.
> > 
> > You've said that `predicate`, `relation`, etc., depending on `__boolean_testable` is motivation for not consolidating into a single `callable.h`. You haven't outlined why it's motivation.
> > 
> > It's also occurred to me overnight that @ldionne may want a consolidated header, as he did for `<functional>`'s function objects. Again, I'm ambivalent on that, but it's something Louis might have a stronger opinion on.
> @ldionne, could you put this subthread to rest, please?
Specifically, this one.


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