On this code I get the enourmous error static void ParseTheCommandLine(int argc, char *argv[]) { int count; int seqNumber; namespace po = boost::program_options; std::string appName = boost::filesystem::basename(argv[0]); po::options_description desc("Generic options"); desc.add_options() ("version,v", "print version string") ("help", "produce help message") ("sequence-number", po::value<int>(&seqNumber)->default_value(0), "sequence number") ("pem-file", po::value< vector<string> >(), "pem file") ; po::positional_options_description p; p.add("pem-file", -1); po::variables_map vm; po::store(po::command_line_parser(argc, argv). options(desc).positional(p).run(), vm); po::notify(vm); if (vm.count("pem file")) { cout << "Pem files are: " << vm["pem-file"].as< vector<string> >() << "\n"; } cout << "Sequence number is " << seqNumber << "\n"; exit(1); ../../../FIXMarketDataCommandLineParameters/FIXMarketDataCommandLineParameters.hpp|98|error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits](((std::basic_ostream &)(& std::cout)), ((const char*)"Pem files are: ")) << ((const boost::program_options::variable_value*)vm.boost::program_options::variables_map::operator[](((const std::string&)(& std::basic_string, std::allocator (((const char*)"pem-file"), ((const std::allocator&)((const std::allocator*)(& std::allocator()))))))))-boost::program_options::variable_value::as with T = std::vector, std::allocator , std::allocator, std::allocator ’|