Why I can not input from archive std::map ? line: inputArchive >> inputContainer causes compile error: Thanks Adam #include <string> #include <iostream> #include <fstream> #include <sstream> #include <map> #include #include #include #include #include #include #include #include #include #include #include class A { public: A() {}; A(std::string const & s): s(s) { } virtual ~A() {}; private: std::string s; friend std::ostream & operator<<(std::ostream & os, A const & a); friend class boost::serialization::access; template<class Archive> void serialize(Archive & archive, unsigned int const version) { archive & s; } }; std::ostream & operator<<(std::ostream & os, A const & a) { return os << a.s; } typedef std::map Container; BOOST_CLASS_TRACKING(Container, boost::serialization::track_never); std::ostream & operator<<(std::ostream & os, Container const & container) { Container::const_iterator end = container.end(); for (Container::const_iterator i = container.begin(); i != end; ++i) { os << "(" << i->first << "," << *i->second << ")" << std::endl; } return os; } int _tmain(int argc, _TCHAR* argv[]) { std::cout << "serialization map test starts" << std::endl; Container outputContainer; outputContainer.insert(std::make_pair(1, new A("one"))); outputContainer.insert(std::make_pair(4, new A("four"))); outputContainer.insert(std::make_pair(2, new A("two"))); std::cout << outputContainer << std::endl; { std::wofstream outputFile("data.txt"); boost::archive::text_woarchive outputArchive(outputFile); outputArchive << outputContainer; } std::cout << "---------------------------" << std::endl; Container inputContainer; { std::wifstream inputFile("data.txt"); boost::archive::text_wiarchive inputArchive(inputFile); inputArchive >> inputContainer; // this line causes compile error } std::cout << inputContainer << std::endl; std::cout << "serialization map test ends" << std::endl; return 0; }