...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::anys::in_place_type_t — Helper type for providing emplacement type to the constructor.
// In header: <boost/any/unique_any.hpp> template<typename T> struct in_place_type_t { };