C++如何用class重载+号实现（a,b)+(c,d)=(a+c,b+d)。

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#include<iostream>
using namespace std;

class A
{
public:
    A(){}
    A(int _a, int _b)
    {
        a = _a;
        b = _b;
    }

    A operator+(A other)
    {
        A a1(a + other.a, b + other.b);
        return a1;
    }
    void show()
    {
        cout << a << "," << b << endl;
    }
private:
    int a;
    int b;
};

int main()
{
    int a = 1, b = 2, c = 3, d = 4;
    A a1(a, b);
    A a2(c, d);
    A a3 = a1 + a2;
    a3.show();
    return 0;
}