http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50880
--- Comment #23 from Richard B. Kreckel <kreckel at ginac dot de> 2011-11-03
23:57:55 UTC ---
(In reply to comment #16)
> Well, I guess this would be most of it:
>
> template<typename _Tp>
> std::complex<_Tp>
> __complex_acosh(const std::complex<_Tp>& __z)
> {
> return _Tp(2.0) * std::log(std::sqrt(_Tp(0.5) * (__z + _Tp(1.0)))
> + std::sqrt(_Tp(0.5) * (__z - _Tp(1.0))));
> }
[Sorry for my temporary absence.]
For future reference, some final remarks:
* Yes, that is a good implementation for this "fallback".
It relies on __z - _Tp(1.0) not "mutating" the sign of __z's imag part.
* If the complex log does not do the right thing, all is lost anyways
(besides, __complex_asinh relies on it, too).
* My patch BC1 was flawed. It contains code trying to work around a ctor doing
multiplication (fixed in PR48760)
* My patch BC2 was flawed for the same reason: __z - __one doesn't preserve
the sign of __z's imag part.
Looks good. Thanks!
