조건에 따라 리턴타입이 다른 함수 만들기?

#include <iostream>
#include <utility>
#include <memory>
#include <vector>
 
using namespace std;
 
template <typename T>
class A {
    private:
        vector< A<T> > *t1;
        T *t2;
        bool flag;
 
    public:
        A<T> &operator[](int idx) { return t1->at(idx); }
 
        A(bool flag = false) : flag(flag) {
            if (flag)
            {
                t1 = new vector< A<T> >();
                t2 = 0;
            }
            else
            {
                t1 = 0;
                t2 = new T();
            }
        }
        ~A() {
        }
 
        bool is_vec() const { return flag; }
 
        operator T() const { return *t2; }
 
        A<T>& operator =(const T& rhs) {
            (*t2) = rhs;
            return *this;
        }
 
        A<T>& operator =(const A<T>& rhs) {
            A<T>& lhs = *this;
 
            if (rhs.t1)
                lhs.t1   = new vector< A<T> >(*(rhs.t1));
            if (rhs.t2)
                lhs.t2   = new T(*(rhs.t2));
            lhs.flag = rhs.flag;
 
            return lhs;
        }
 
        size_t size() const {
            return t1->size();
        }
 
        void resize(size_t size) {
            t1->resize(size);
        }
};
 
int main()
{
    A<int> l1(false);
    A<int> l2(false);
    A<int> l3(false);
    A<int> l4(false);
    A<int> l5(false);
    A<int> c1(true);
    A<int> c2(true);
 
    l1 = 71;
    l2 = 10;
    l3 = 9;
    l4 = 17;
    l5 = 20;
 
    c1.resize(3);
    c1[0] = l1;
    c1[1] = l2;
    c1[2] = l3;
 
    c2.resize(3);
    c2[0] = l4;
    c2[1] = l5;
    c2[2] = c1;
 
    cout << c2[0] << endl;
    cout << c2[1] << endl;
    cout << c2[2][0] << endl;
    cout << c2[2][1] << endl;
    cout << c2[2][2] << endl;
 
    return 0;
}
 
// EOF