Re: bug - boost::math::ccmath::copysign not work

From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2022-08-18 06:23:38

bit_cast is constexpr.

On Thu, 18 Aug 2022, 03:25 Proton via Boost, <boost_at_[hidden]> wrote:

> > On Aug 17, 2022, at 4:11 PM, Gero Peterhoff via Boost <
> boost_at_[hidden]> wrote:
> >
> > Hi,
> > I just see that boost::math::ccmath::copysign doesn't work.
> > https://godbolt.org/z/9af1ME9fT
> >
> > cu
> > Gero
> >
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>
> Gero,
>
> The typical implementation of copysign and signbit involve type-punning
> which is not allowed in constexpr contexts. An example can be found here:
> https://android.googlesource.com/platform/bionic.git/+/brillo-m7-dev/libm/signbit.c.
> Due to this limitation we do not provide support for signed zero or
> analyzing the sign of NAN.
>
> Matt
>
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