Hello, I'm using program_options, and I want to be able to learn what the option type is by manipulating an options_description object. As I illustrate in the example below (boost 1.33), I can do this if the option has been given a default value. Could anyone suggest a wasy to this for options without a default? The story behind this question is that I would like to be able to build a simple GUI parameter dialog based on the options_description, and I want to map different types to different widgets. Thanks, Giuseppe #include <boost/program_options.hpp> #include <boost/filesystem/path.hpp> #include <iostream> #include <vector> #include <string> #include <algorithm> #include <iterator> template<typename T> bool type_is (const boost::any & v) { return v.type() == typeid(T); } struct MyType { MyType() : x(0) {} MyType(double d) : x(d) {} double x; }; std::ostream & operator<<(std::ostream & os, const MyType & mt) { os << mt.x; return os; } std::istream & operator>>(std::istream & is, MyType & mt) { is >> mt.x; return is; } using namespace std; namespace po = boost::program_options; int main(int ac, char * av[]) { typedef vector<string> type; po::options_description desc1("Allowed options 1"); desc1.add_options() ("switch", po::value<bool>(), " a boolean switch") ("numbers", po::value<type>(), "a list of numbers") ("number", po::value<double>()->default_value(42), "the number") ; po::options_description desc2("Allowed options 2"); desc2.add_options() ("mytype", po::value<MyType>()->default_value(MyType(123.4)), "my type") ; po::options_description cmdlinedesc; cmdlinedesc.add(desc1).add(desc2); po::variables_map vm; po::store(po::parse_command_line(ac, av, cmdlinedesc), vm); po::notify(vm); typedef std::vector< boost::shared_ptr<po::option_description> > VOD; const VOD & pk = cmdlinedesc.options(); for(VOD::const_iterator K = pk.begin(); K != pk.end(); ++K){ cout << " [ " << (*K)->long_name() << " - " << (*K)->description() << " ] "; boost::shared_ptr< const po::value_semantic > sem = (*K)->semantic(); boost::any default_store; bool has_default = sem->apply_default(default_store); if(has_default) cout << " has default "; if(type_is<double>(default_store)) cout << " = (double) " << boost::any_cast<double>(default_store); if(type_is<bool>(default_store)) cout << " = (bool) " << boost::any_cast<bool>(default_store); if(type_is<MyType>(default_store)){ MyType x = boost::any_cast<MyType>(default_store); cout << " = (MyType) " << x; } cout << endl; } }