#include <iostream>
using namespace std;

//成员函数重载
class Person {
    public:
        Person operator+(Person &p) {
            Person temp;
            temp.m_A = this->m_A + p.m_A;
            temp.m_B = this->m_B + p.m_B;
            return temp;
        }
        
        int m_A;
        int m_B;
};


//全局函数重载 
Person operator-(Person &p1, Person &p2) {
    Person temp;
    temp.m_A = p1.m_A - p2.m_A;
    temp.m_B = p1.m_B - p2.m_B;
    return temp;
}

int main() {
    Person p1;
    p1.m_A = 10;
    p1.m_B = 10;
    Person p2;
    p2.m_A = 10;
    p2.m_B = 10;
    
    Person p3 = p1 + p2;
    cout << p3.m_A << " " << p3.m_B << endl; // 20 20
    
    Person p4 = p1 - p2;
    cout << p4.m_A << " " << p4.m_B << endl; // 0 0
} 

#include <iostream>
using namespace std;

class Person {
    friend ostream & operator<<(ostream &cout, Person &p);
    
    public:
        Person(int a, int b) {
            m_A = a;
            m_B = b;
        } 
        
    private:
        //operator<<(cout)  相当于 p.operator<<(cout) 简化为 p << cout; 
        // 顺序不是 cout << p;这样的预期效果，所以一般不用成员函数重载 

        int m_A;
        int m_B;
};

//流对象不能复制，只能引用&cout 
ostream & operator<<(ostream &cout, Person &p) { //本质 operator(cout, p) 简化 cout << p; 
    cout << "m_A = " << p.m_A << " " << "m_B = " << p.m_B;
    return cout; //链式编程思想 可以在后面接endl了 
}


int main() {
    Person p(10, 10);

//以前的<<功能不变，追加了输出Person对象的功能 
    cout << p << endl;
} 

#include <iostream>
using namespace std;

class MyInteger {
    friend ostream & operator<<(ostream &cout, MyInteger myint);
    public:
        MyInteger() {
            m_Num = 0;
        } 
        
        //重载前置++运算符 
        MyInteger& operator++() { //返回引用 是为了一直对一个数据进行递增操作 
            //先自增 
            m_Num++;
            //后返回 
            return *this;
        }
        
        //重载后置++运算符 
        MyInteger operator++(int) { //int代表占位参数，可以用于区分前置递增和后置递增 
            //先记录当时结果 
            MyInteger temp = *this;
            //后 递增
            m_Num++;
            //最后将记录结果返回 
            return temp;      //temp是局部对象，不要返回引用
        }
    private:
        int m_Num;
};

//重载左移运算符 
ostream & operator<<(ostream &cout, MyInteger myint) {
    cout << myint.m_Num;
    return cout;
} 


int main() {
    MyInteger myint;
    cout << myint << endl; //0
    
    cout << ++myint << endl;//1
    cout << myint++ << endl;//1
    cout << myint << endl;//2
}