Date: Sat, 23 Sep 2023 11:52:19 -0400
On Sat, Sep 23, 2023 at 11:45 AM Chris Gary via Std-Proposals
<std-proposals_at_[hidden]> wrote:
>
> All computable data can be made isomorphic to integers.
> It is always possible to define a total ordering.
> Even N-d points have a total ordering in the form of space-filling curves.
> N-d rational points are the same: Reduce the coordinates so they are unique, then either use zig-zag or interleave the bits numerator then denominator to get a Morton index for some weird N+1 or 2*N dimensional space (not the same in the spatial sense, but this at least allows them to be used in an ordered container).
>
> For all scalar types, spaceship could become int-valued and return the sign of the difference in the form of an int.
>
> Let the ordering in the case of an 'int'-valued operator <=> be assumed the same as std::strong_order where it is not otherwise defined explicitly.
>
> In the context of deducing the result type of operator <=>, it could be allowed either for backwards compatibility. That, or implicit "cast" of "int" to a "std::strong_order" where it is required.
>
> Frankly, I've avoided using operator <=> due to header issues and the strangeness of a formal operator returning a privileged type in namespace std. I wouldn't be surprised if I've missed a detail...
Why?
Why does the standard need to change this? Because you don't like
having an operator return a "privileged type in namespace std"? Why
should that matter? It's not like `typeid` hasn't done that since
C++98. It's not like list initialization as a language feature is not
fundamentally bound to the `std::initializer_list` type.
What is the advantage of returning an integer instead of a specific
kind of ordering? Will it improve performance? Will it fix some actual
problem programmers will have? Or is it just personal preference?
<std-proposals_at_[hidden]> wrote:
>
> All computable data can be made isomorphic to integers.
> It is always possible to define a total ordering.
> Even N-d points have a total ordering in the form of space-filling curves.
> N-d rational points are the same: Reduce the coordinates so they are unique, then either use zig-zag or interleave the bits numerator then denominator to get a Morton index for some weird N+1 or 2*N dimensional space (not the same in the spatial sense, but this at least allows them to be used in an ordered container).
>
> For all scalar types, spaceship could become int-valued and return the sign of the difference in the form of an int.
>
> Let the ordering in the case of an 'int'-valued operator <=> be assumed the same as std::strong_order where it is not otherwise defined explicitly.
>
> In the context of deducing the result type of operator <=>, it could be allowed either for backwards compatibility. That, or implicit "cast" of "int" to a "std::strong_order" where it is required.
>
> Frankly, I've avoided using operator <=> due to header issues and the strangeness of a formal operator returning a privileged type in namespace std. I wouldn't be surprised if I've missed a detail...
Why?
Why does the standard need to change this? Because you don't like
having an operator return a "privileged type in namespace std"? Why
should that matter? It's not like `typeid` hasn't done that since
C++98. It's not like list initialization as a language feature is not
fundamentally bound to the `std::initializer_list` type.
What is the advantage of returning an integer instead of a specific
kind of ordering? Will it improve performance? Will it fix some actual
problem programmers will have? Or is it just personal preference?
Received on 2023-09-23 15:52:31