Overloaded Circle() is ambiguous in C++ Circle Class - c++

Question

I am currently trying to create a circle class in C++ but when I compile I get an error saying "call of overloaded 'Circle' is ambiguous. I am quite new to C++ and not sure what this means. I have been using a similar example found here Class tutorial
#include <iostream>
using namespace std;
const double pi = 3.14159265;
class Circle
{
private:
double radius, xpos, ypos, area;
public:
Circle(double r, double xposition, double yposition) {
r = radius;
xposition = xpos;
yposition = ypos;
}
Circle(double r = 0) {
radius = r;
xpos = 0;
ypos = 0;
}
Circle() {
radius = 0;
xpos = 0;
ypos = 0;
}
double getRadius() {return radius;}
double getX() {return xpos;}
double getY() {return ypos;}
double getArea() {return pi*radius*radius;}
Circle operator+(const Circle& c) {
Circle circle;
circle.area = this -> getArea() + c.getArea();
return circle;
}
};
int main()
{
Circle circ(3,2,1);
double x = circ.getX();
cout << x << endl;
return 0;
}

Answer 1

Your problem is this:
Circle(double r = 0);
Circle();
Nothing much more to say about it that isn't already obvious from the above.
The default value in Circle(double r = 0) makes the use of Circle() ambiguous.
By the way, you've got your member variable initialization all wrong here:
Circle(double r, double xposition, double yposition)
{
r = radius;
xposition = xpos;
yposition = ypos;
}
Instead of setting the member variables to the values of the input arguments, you are setting the input arguments to the "junk" values of the member variables...

Answer 2

You have two different constructors that can be called with no parameters, because one of them has a default for the parameter. You can delete the default constructor, since it's redundant.