struct CClass
{
    int m_a, m_b, m_c;
    CClass(int a, int b, int c): m_a(a), m_b(b), m_c(c){}
};

std::ostream &operator <<(std::ostream &stream, const CClass &c)
{
    stream << c.m_a << " " << c.m_b << " " << c.m_c;
    return stream;
}

std::istream &operator >>(std::istream &stream, CClass &c)
{
    stream >> c.m_a >> c.m_b >> c.m_c;

    return stream;
}

int main(int , char **)
{
    CClass c(1,2,3);

    std::cout << c << std::endl;
    std::cin >> c;
    std::cout << c << std::endl;

    return 0;
}

int my_var = my_map[var_name];
// много обращений к переменной