...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::type_erasure::subtract_assignable
// In header: <boost/type_erasure/operators.hpp> template<typename T = _self, typename U = T> struct subtract_assignable { // public static functions static void apply(T &, const U &); };