C++ 面向对象编程：+号运算符重载，左移运算符重载

像+、-号进行运算符重载，过程类似，见以下代码示例：

#include<iostream>
#include<string>
using namespace std;

class number1 {
    friend number1 operator+(number1& one, number1& two);
public:
    number1():msg1(0), msg2(1){}
    number1(int msg1, int msg2) {
        this->msg1 = msg1;
        this->msg2 = msg2;
    }
    void Print() {
        cout << msg1 << "+" << msg2 << endl;
    }
private:
    int msg1;
    int msg2;
};

number1 operator+(number1& one, number1& two) {
    number1 num1;
    num1.msg1 = one.msg1 + two.msg1;
    num1.msg2 = one.msg2 + two.msg2;
    return num1;
}

int main() {
    number1 a(1, 2);
    number1 b(2, 3);
    number1 c = a + b;
    c.Print();
    return 0;
}

左移运算符一般是这种样式：对象为e的话，cout.operator<<(e)，成员函数的重载是这样的：

e.opeerator<<(cout)，可以作为当前类的成员函数，这样就可以实现对象的输出，见以下代码示例

#include<iostream>
#include<string>
using namespace std;

class number1 {
	friend number1 operator+(number1& one, number1& two);
	friend ostream& operator<<(ostream& cout, number1 a);
public:
	number1():msg1(0), msg2(1){}
	number1(int msg1, int msg2) {
		this->msg1 = msg1;
		this->msg2 = msg2;
	}
	void Print() {
		cout << msg1 << "+" << msg2 << endl;
	}
private:
	int msg1;
	int msg2;
};

number1 operator+(number1& one, number1& two) {
	number1 num1;
	num1.msg1 = one.msg1 + two.msg1;
	num1.msg2 = one.msg2 + two.msg2;
	return num1;
}

ostream& operator<<(ostream& cout, number1 a) {
	cout << a.msg1 << a.msg2 << endl;
	return cout;
}

int main() {
	number1 a(1, 2);
	number1 b(2, 3);
	number1 c = a + b;
	c.Print();
	cout << c << endl;
	return 0;
}