dictionary - c++ using structs as data for a <map, <map, vector>> -

i having problem trying load map has map/vector combination value structs. below code have tried simplify as could:

    //these structs     struct order      {         std::string a;         std::string b;     };      struct card     {         std::string c;         std::string d;     };      struct item       {         std::string e;         std::string f;     };      //this method read , load map     void loadmap(listofvalues object)     {     std::map<order, std::map<item, std::vector<card>>> records; //this data structure i'm trying store      //listofvalues list passed holds these values need put map     for(std::vector<listofvalues>::iterator viter= object.begin(); viter != object.end(); ++viter)             {                            std::string sreceiptrecord = (*viter).getreceipt(m_stdorderconfirmver);                  order order = {(*viter).geta,(*viter).getb};                  item item = {(*viter).getc,(*viter).getd};                  card card = {wws::string((*viter).gete), (*viter).getf};                   records[order][item].push_back(card); //load map                         }       } 

so have object passed contains list of values (listofvalues). iterate through list , getter methods, store values structs (gete returns long why conversion necessary). there step i'm missing

an error i'm getting is:

error c2678: binary '<' : no operator found takes left-hand operand of type 'const order' (or there no acceptable conversion) 

you need provide operator < struct used key map, see question: struct key in std::map