Cuong

class A
{
       public:
        A(){num = 0;}
        ~A(){}
        void method() const{}
        int& operator [] (int i) const {return num;}
        int num;

};

void call( A &a)
{
    a.method();

}

int main()
{
    A a;
    call(a);
    return 0;
}