On 04/02/2021 20:23, Gero Peterhoff via Boost wrote:
Hello Chris, Unfortunately, a few things have come up with me so that I (probably) won't be able to really help in the near future. Some other functions (e.g. log, exp) also give incorrect results for some combinations of nan, inf and 0.
The place to check for this is C99 Annex G - but note that this is non-normative so there will be implementations of std::complex which do not do anything in particular in these cases... platforms too with no infinity or NaN.
But I saw that gcc libquadmath (https://gcc.gnu.org/onlinedocs/libquadmath/Math-Library-Routines.html#Math-L...) offers some complex functions that work correctly. These could be used. But I don't know if clang, intel and/or other compilers can do that too. example inline complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE> log(const complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE>& x) { __complex128 res = __complex128{x.real(), x.imag()}; res = clogq(res); return complex<BOOST_CSTDFLOAT_EXTENDED_COMPLEX_FLOAT_TYPE>{crealq(res), cimagq(res)}; }
I also noticed a few basic things, maybe you can say why that is: - Why are there explicit complex classes for FP types, why is this not implemented completely via template? The advantage is that built-ins can be used, on the other hand, a separate class must be written for each FP type - with the problems we are currently having. This is all a question for the C++ committee, my speculation would be that they wished to restrict the scope of std::complex to float/double/long double. - Why are there missing template conversion ctors for the complex<FP-Type>? That will not do: std::complex<int> ci{4711, 23}; std::complex<double> cd=ci; or std::complex<double> cd = std::complex<double>{ci}; but a ctor must be called explicitly std::complex<double> cd=std::complex<double>{double(ci.real()), double(ci.imag())}; // prevent warnings It's really annoying. - Why are many std-math functions missing for complex; special-functions complete (also applies to std::valarray)?
I want to add such things in my math-lib, as far as possible everything constexpr. I also want to provide additional classes for dual and splitcomplex numbers (i²=0, i²=1, but it is far from complete - because it is quite extensive). Maybe these could also be included in boost. To do this, however, it would be necessary to convert the boost-math-lib to C++20, since some functions (or the distinction between dual, complex and splitcomplex - classes/functions) is only possible with concepts (otherwise unreasonable effort). I also need some additional typetraits.
If you want to provide implementations for any complex valued special functions we can take care of the algorithm overload selection - enable_if will do fine, there's no need for concepts just yet. Best John. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus