C++ another class member and overloading operator - c++

Question

I need to write program as follow:
#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;
}
Two classes Point and Circle, where Circle have member of Point as it's center, two operators to add and to subtract two Circles.
And I can't compile this, what is wrong?
#################################################################################
EDIT:
After correction it looks like that, and works perfectly:
#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;
}

Answer 1

When you define operators like operator- inside your class as member functions, then when you use it
C3 = C1 + C2;
The compiler is actually calling your member function like
C3 = C1.operator+(C2);
From this you should be able to figure out that operators as member functions only takes one argument, and that the first object in the operator is the this object.
For stand-alone (non-member) functions they need two arguments.
You might want to check e.g. this reference on operator overloading.

Answer 2

You have incorrect overloaded operators. Look at the following code:
Circle operator +(const Circle& C)
{
return Circle(this->P, this->R + C.R);
}
Circle operator -(const Circle& C)
{
return Circle(this->P, this->R - C.R);
}