I have experimented with the quadmath library included with gcc and the boost::math::constants library and encountered several problems.
- typeid is seemingly not supported for __float128, which requires an overload of nameof<__float128> - the stream extraction operator has to be provided for __float128 for string conversion to work - a specialisation of numeric_limits has to be provided.
Is there an interest in incorporating __float128 into boost ? If so, would it be a good idea to specialise constants for __float128 as well, apart from float, double and long double?
Funnilly enough I wondered about this the other day, but haven't had the time to do anything about it. Plus I've rather been hoping that the GCC guys would make __int128 and __float128 first class citizens and render the issue moot ;-) An open question is whether we should add a "binding" header under boost/math/bindings or whether it would be better to wrap __float128 and libquadmath as a multiprecision type under boost/multiprecision. The latter option has the advantage that we don't have to pollute the global namespace with std lib overloads for __float128. Of course a simpler solution is possible if you just want the numeric constants working for __float128, but it would be nice to make the type a first class C++ type that interoperates with all of Boost.Math. John.