[Boost-users] boost program options - notifier function 0 arguments

Hello I've been wondering how its possible to call a notifier function with an option that doesnt require arguments. Something like: po::options_description desc("Allowed options"); desc.add_options() ("help", po::value<>()->notifier(&_help_function), "produce help message"); Whats the proper way of doing this? Many thanks in advance Aljaz