Re: BOOST_IS_CONSTANT_EVALUATED_INT(integer-expression)(integer-expression)

From: Ivan Matek (libbooze_at_[hidden])
Date: 2021-08-22 23:36:40

On Sun, Aug 22, 2021 at 10:29 PM Robert Ramey via Boost <
boost_at_[hidden]> wrote:

>
> Yes.... but the function should really return the same value in both
> constexpr and runtime usage.
>
> LOL - for me, the whole point of this is to use a different value
> depending on whether or not the value is known at compile time. Maybe
> someone wants to opine on this.
>
I think it would help discussion if you or John could provide a complete
use case when different result is desired for a function depending on if it
is running at compile time or not?
I never had the need for different result based on if function is running
at compile time, I have read the paper that proposed
std::is_constant_evaluated (
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0595r2.html ), and
I did not find that example, except maybe their mention of constexpr
std::string, but I presume that is mostly hacks to go around constexpr
limitations, I think they still want to to implement same logic for
std::string.