[笔记]模版类中重载<<操作符

//text.cpp
#include <ostream>
using namespace std;

template<typename E>
class Text()
{
    friend ostream& operator<<(ostream& os, T<E>& te);

private:
    E e;
}

template<typename E>
ostream& operator<<(ostream& os, T<E>& te)
{
    return os<<te.e;
}

//text.cpp
#include <ostream>
using namespace std;

template<typename E>
class Text()
{
    template<typename E1>
    friend ostream& operator<<(ostream& os, T<E1>& te);

private:
    E e;
}

template<typename E1>
ostream& operator<<(ostream& os, T<E1>& te)
{
    return os<<te.e;
}

//text.cpp
#include <ostream>
using namespace std;

template<typename E>
class Text()
{
    friend ostream& operator<<(ostream& os, T<E>& te)
    {
        return os<<te.e;
    }

private:
    E e;
}