c++的另一个类成员和重载操作符

我需要编写如下程序:

#include <iostream>
using namespace std;
class Point
{
    public:
        double X;
        double Y;
        Point(){}
        Point(double x, double y)
        {
            X = x;
            Y = y;
        }
};
class Circle
{
    public:
        Point P;
        double R;
        Circle(){}
        Circle(Point p, double r)
        {
            P = p;
            R = r;
        }
        Circle operator +(Circle C1, Circle C2)
        {
            return Circle(C1.Point, C1.R + C2.R);
        }
        Circle operator -(Circle C1, Circle C2)
        {
            return Circle(C2.Point, C1.R - C2.R);
        }
};
int main()
{
    Circle c1, c2, cr1, cr2, ck1, ck2;
    // create c1
    // create c2
    cr1 = c1 + c2;
    // display cr1
    cr2 = c2 + c1;
    // display cr2
    ck1 = c1 - c2;
    // display ck1
    ck2 = c2 - c1;
    // display ck2
    return 0;
}

两个类Point和Circle，其中Circle以Point的成员为中心，两个操作符分别对两个Circle进行加减运算。

我不能编译这个，怎么了?

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编辑:修改后看起来像这样，并且工作完美:

#include <iostream>
using namespace std;
class Point
{
    public:
        double X, Y;
        Point(){}
        Point(double x, double y)
        {
            X = x;
            Y = y;
        }
};
class Circle
{
    public:
        double R;
        Point P;
        Circle(){}
        Circle(Point p, double b)
        {
            P = p;
            R = b;
        }
        Circle operator+(const Circle& C1)
        {
            Circle C;
            C.P = this->P;
            C.R = this->R + C1.R;
            return C;
        }
        Circle operator -(const Circle& C1)
        {
            Circle C;
            C.P = C1.P;
            C.R = this->R - C1.R;
            return C;
        }
};
int main()
{
    double X, Y, R;
    cout << "Coordinates for C1:" << endl;
    cout << "tX: ";
    cin >> X;
    cout << "tY: ";
    cin >> Y;
    cout << "Radius for C1:";
    cin >> R;
    Circle *c1 = new Circle(Point(X, Y), R);
    cout << "Coordinates for C2:" << endl;
    cout << "tX: ";
    cin >> X;
    cout << "tY: ";
    cin >> Y;
    cout << "Radius for C2:";
    cin >> R;
    Circle *c2 = new Circle(Point(X, Y), R);
    Circle cs1 = c1->operator+(*c2);
    Circle cs2 = c1->operator-(*c2);
    Circle cr1 = c2->operator+(*c1);
    Circle cr2 = c2->operator-(*c1);
    cout << "cs1([" << cs1.P.X << ", " << cs1.P.Y << "], " << cs1.R << ")" << endl;
    cout << "cs2([" << cs2.P.X << ", " << cs2.P.Y << "], " << cs2.R << ")" << endl;
    cout << "cr1([" << cr1.P.X << ", " << cr1.P.Y << "], " << cr1.R << ")" << endl;
    cout << "cr2([" << cr2.P.X << ", " << cr2.P.Y << "], " << cr2.R << ")" << endl;
    char ch;
    cin >> ch;
    return 0;
}