...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::program_options::required_option
// In header: <boost/program_options/errors.hpp> class required_option : public boost::program_options::error_with_option_name { public: // construct/copy/destruct required_option(const std::string &); ~required_option(); };