On Mon, 13 Apr 2020 at 15:33, Michael Hava via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> *IMHO:* The definition of numeric_limits is rather unfortunate (
> is_specialized, min vs lowest, countless members that have no meaning for
> certain types, …), but I seriously doubt that we can/should try to change
> it after 20+ years…
>
>
>
> If anything can be done in this area, it should most probably be a new
> facility for these limits that follows a more modern (read: non-monolithic)
> design.
>

See P0437R1
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0437r1.pdf> and
P1370R1
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1370r1.html> for
work in this direction.

Note: type_traits already exposes some of the functionality of
> numeric_limits (is_signed, is_integral, …).
>

>
> Best regards,
>
> Michael
>
>
>
> Food for thought: maybe a new limits-system should include support for
> “custom arithmetic types” (e.g. complex,…)
>

It should although numeric_limits does allow custom specialization.

Cheers,
John

>
>
> *From:* Std-Proposals <std-proposals-bounces_at_[hidden]> *On Behalf
> Of *Thomas Mercier via Std-Proposals
> *Sent:* Friday, April 10, 2020 8:27 PM
> *To:* std-proposals_at_[hidden]
> *Cc:* Thomas Mercier <thomas.mercier.jr_at_[hidden]>
> *Subject:* [std-proposals] Make non-specialized numeric_limits<T> use
> ill-formed
>
>
>
> Hi,
>
> I encountered some surprising behavior from the std::numeric_limits<T>
> class template when experimenting with std::byte. The integer
> representation of the maximum std::byte value is 0 according to
> std::numeric_limits<std::byte>::max(). That is because there is no
> specialization of std::numeric_limits<T> for std::byte, because std::byte
> is not an arithmetic type. Ok, fine. But the fact that the program
> compiles, and produces an unexpected value is worrisome!
>
> The standard specifies that "The default numeric_­limits<T> template shall
> have all members, but with 0 or false values." (
> https://eel.is/c++draft/numeric.limits#3)
>
> I would prefer to see this say something like, "a program which uses the
> default numeric_limits<T> template is ill-formed", so that an error is
> produced at compile time rather than a value initialized result (
> https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/std/limits#L321
> and
> https://github.com/llvm/llvm-project/blob/master/libcxx/include/limits#L150
> ).
>
> Does anyone know why the current wording specifies "0 or false values", or
> what any objections to my suggested change might be?
>
> https://godbolt.org/z/YVSECn
>
> Thanks,
> T.J.
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