...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::units::abstract::solid_angle_unit_tag
// In header: <boost/units/systems/abstract.hpp> struct solid_angle_unit_tag : public base_unit< solid_angle_unit_tag, solid_angle_dimension,-22 > { };