...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::numeric::functional::promote<bool const, From, void, std_valarray_tag>
// In header: <boost/accumulators/numeric/functional/valarray.hpp> template<typename From> struct promote<bool const, From, void, std_valarray_tag> : public boost::numeric::functional::promote< bool, From, void, std_valarray_tag > { };