我想知道我的目标是否可行.
我有一个类Class
#include<iostream>
template<class T> class Class;
template<class T, class W> Class<W> f(Class<T>& C, const Class<T>& D);
template<class T> class Class {
protected: // this could be private
T m_t;
public:
Class(): m_t(T()) {}
Class(T t): m_t(t) {}
T& getT() { return m_t; }
template<class U, class W> friend Class<W> f(Class<U>& C, const Class<U>& D);
};
template<class T, class W> Class<W> f(Class<T>& C, const Class<T>& D)
{
C.m_t += D.m_t;
Class<W> R;
std::cout << R.m_t << std::endl; // I don't …