The point is that you can tag a class from outside, that you can choose whether to include derived classes and especially

that no core language change is necessary.
 

-----Ursprüngliche Nachricht-----
Von: Frederick Virchanza Gotham via Std-Proposals <std-proposals@lists.isocpp.org>
Gesendet: Do 17.04.2025 16:42
Betreff: Re: [std-proposals] std::arithmetic (concept)
An: std-proposals@lists.isocpp.org;
CC: Frederick Virchanza Gotham <cauldwell.thomas@gmail.com>;
On Thu, Apr 17, 2025 at 12:17 PM Sebastian Wittmeier wrote:
>
> template <typename T>
> requires std::is_base_of_v<MyString, std::remove_cvref_t<T>>
> constexpr bool enable_arithmetic<T> = true;


Not sure what point you're making here other than to say that there's
half a dozen ways of 'tagging' a class. I'm least keen on the strategy
of using an empty base class as a tag, however it might have benefits
when it comes to dynamic_cast.
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