Ok, this is my code: #include <boost/multi_index_container.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/random_access_index.hpp> using namespace boost::multi_index; template<typename K,typename V> //K = Key, V = Value class Ordered_Map { private: struct mutable_pair { typedef K first_type; typedef V second_type; mutable_pair():first(K()),second(V()){} mutable_pair(const K& f,const V&s):first(f),second(s){} mutable_pair(const std::pair<K,V>& p):first(p.first),second(p.second){} K first; mutable V second; }; typedef multi_index_container< mutable_pair, indexed_by< random_access<>, ordered_unique<member<mutable_pair, K, &mutable_pair::first> > > > container1; container1 c; mutable_pair *r; public: V& operator[]( const K& key ) { r = new mutable_pair(key,V()); c.insert(c.end(),*r); return (*r).second; } typename container1::const_iterator cbegin() const { return c.cbegin(); } typename container1::const_iterator cend() const { return c.cend(); } }; int main() { Ordered_Map<std::string,int> myMap; myMap["Joe"] = 3; myMap["Lillo"] = 9; myMap["Mary"] = -3; for (auto i = myMap.cbegin(); i != myMap.cend(); ++i) std::cout << i->first << " - " << i->second << std::endl; std::cin.get(); return 0; } I now correctly get two iterators, but in this class don't work the assignment: my output is: Joe - 0 Lillo - 0 Mary - 0 -- View this message in context: http://boost.2283326.n4.nabble.com/Container-with-insertion-order-tp4097717p... Sent from the Boost - Users mailing list archive at Nabble.com.