c++ - how to display class data members stored in multimap -

here code

class student { int num; string name; float marks; public: void add() {     cout << "enter num name , marks:" << endl;     cin >> num >> name >> marks; } void display() {     cout << num << endl;     cout << name << endl;     cout << marks << endl; } }; void main() { student ss; multimap<int,student> st; multimap<int,student>::iterator itr;     ss.add();     st.insert(make_pair(1000, ss));  (itr = st.begin(); itr != st.end(); itr++) {     cout << itr->second; // showing error  } } 

the error error c2679 binary '<<': no operator found takes right-hand operand of type 'student' (or there no acceptable conversion) firstmultimap
how fix this

to display student object need overload << operator.

i have made operator overloading function friend of student class called without creating object.

also, check example on msdn.

example:

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#include<iostream> #include<map> #include<string> using namespace std; class student { private:     int num;     string name;     float marks; public:     void add()     {         cout << "enter num name , marks:" << endl;         cin >> num >> name >> marks;     }     void display()     {         cout << num << endl;         cout << name << endl;         cout << marks << endl;     }     friend ostream &operator << (ostream &output, const student &s)     {         output << "num: " << s.num << "\nname: " << s.name << "\nmarks: " << s.marks << endl;         return output;     } };  int main() {     student ss;     multimap<int, student> st;     multimap<int, student>::iterator itr;     ss.add();     st.insert(make_pair(1000, ss));     (itr = st.begin(); itr != st.end(); itr++)     {         cout << itr->second;     }     // using range based loop     // for(const auto &i : st)     //     cout << i.second;     return 0; }