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The map is a template that uses a key to obtain a value.
Another issue is that you will want to use your own classes instead of data types, like int that has been used up to now. To create a class that is "template-ready", you must be ensure that the class contains certain member functions and operators. The basics are:

• default constructor (empty, usually)
• copy constructor
• overload "="

You would overload more operators as required in a specific template, for example, if you plan to have a class that is a key in a map you would have to overload relational operators. But that is another story.

// Program: Map Own Class
// Purpose: To demonstrate a map of classes
#include <string> 
#include <iostream> 
#include <vector> 
#include <map> 
using namespace std;
class CStudent
{
public :
int nStudentID;
int nAge;
public :
// Default Constructor - Empty
CStudent()  {  }
// Full constructor
CStudent(int nSID, int nA)  {  nStudentID=nSID; nAge=nA;  }
// Copy constructor
CStudent(const CStudent& ob)  
{  nStudentID=ob.nStudentID; nAge=ob.nAge;  }
// Overload =
void operator = (const CStudent& ob)  
{  nStudentID=ob.nStudentID; nAge=ob.nAge;  }
};
int main(int argc, char* argv[])
{
map <string, CStudent> mapStudent;
mapStudent["Joe Lennon"] = CStudent(103547, 22);
mapStudent["Phil McCartney"] = CStudent(100723, 22);
mapStudent["Raoul Starr"] = CStudent(107350, 24);
mapStudent["Gordon Hamilton"] = CStudent(102330, 22);
// Access via the name
cout << "The Student number for Joe Lennon is " << 
(mapStudent["Joe Lennon"].nStudentID) << endl;
return 0;
}

To avoid an annoying error code in debug mode, use the following compiler pragma:

 #pragma warning(disable: 4786)
                

Another gotcha is: you must make sure that the spaces are placed between your angle brackets and the name. This is because >> is the bit shift operator, so:

  vector <list<int>> veclis;
                

will give an error. Instead, write it:

 vector <list <int> > veclis;
                

to avoid compilation errors.