boost::cnv::reference
// In header: <boost/convert.hpp> template<typename Converter, typename TypeOut, typename TypeIn> struct reference { // types typedef reference this_type; // construct/copy/destruct reference(Converter const &); reference(Converter &&); // public member functions this_type & value_or(TypeOut const &); TypeOut operator()(TypeIn const &) const; };
reference
public member functionsthis_type & value_or(TypeOut const & fallback);
TypeOut operator()(TypeIn const & value_in) const;