Sorry, I posted the wrong test2.cpp, here is the correct one. F. #include "mic_visualizer.hpp" #include <string> #include <boost/multi_index_container.hpp> #include <boost/multi_index/sequenced_index.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/ordered_index.hpp> using namespace boost::multi_index; using std::wstring; using namespace std; struct test { wstring x; wstring y; test(wchar_t const *str, wchar_t const *str2=L"def") : x(str), y(str2) {} bool operator<(test const& other) const { return x<other.x; } }; typedef multi_index_container<test, indexed_by<sequenced<>, ordered_unique<identity<test> > > > cont; VISUALIZE_MULTI_INDEX_CONTAINER(cont); int wmain() { cont test_cont; test_cont.push_back(test(L"aaa")); test_cont.push_back(test(L"bbb")); test_cont.push_back(test(L"ccc", L"ddd")); return 0; // see screenshot }