c – 如何在boost :: program_options中指定vector的默认值

我想为代码中的注释中给出位置参数的默认值,但编译器抱怨.代码正在编译好.我用boost 1.46.1和g

int main(int argc,char *argv[]) {
    namespace po = boost::program_options;

    po::positional_options_description p;
    p.add("path",-1);

    po::options_description desc("Options");
    std::vector<std::string> vec_str;
    std::string str;
    desc.add_options()
        ("foo,f",po::value< std::string >()->default_value(str),"bar")
        //("path,p",po::value< std::vector<std::string> >()->default_value(vec_str),"input files.")
        ("path,po::value< std::vector<std::string> >(),"input files.")
    ;

    po::variables_map vm;
    po::store(po::command_line_parser(argc,argv).options(desc).positional(p).run(),vm);
    po::notify(vm);
}

("path,po::value< std::vector<std::string> > ()->default_value(std::vector<std::string>(),""),"input files.")

std::cout << desc << std::endl;