Inheritance Example: Point and Color_point

// color_point.cpp

#include "cmpt_error.h"
#include <iostream>
#include <cmath>

using namespace std;

class Point {
public:
        double x = 0.0;
        double y = 0.0;

        Point() { }

        Point(double a, double b)
        : x(a), y(b)
        { }

        double dist_to(const Point& other) const {
                double dx = x - other.x;
                double dy = y - other.y;
                return sqrt(dx*dx + dy*dy);
        }

}; // Point

class Color_point : public Point {
        int r = 0;
        int g = 0;
        int b = 0;
public:
        Color_point(double x, double y, int init_r, int init_g, int init_b)
        : Point(x, y),   // call constructor of parent class
          r(init_r), g(init_g), b(init_b)
        {
                if (r < 0 || r > 255) cmpt::error("red out of range");
                if (g < 0 || g > 255) cmpt::error("green out of range");
                if (b < 0 || b > 255) cmpt::error("blue out of range");
        }

        int red() const { return r; }
        int green() const { return g; }
        int blue() const { return b; }
}; // Color_point


int main() {
        Color_point a{1, 20, 100, 50, 75};
        cout << a.x << " " << a.y << "\n";
        cout << a.red() << " " << a.green() << " " << a.blue() << "\n";

        Color_point b{0, 0, 0, 0, 0};
        cout << a.dist_to(b) << " " << b.dist_to(a) << "\n";

        // Point and Color_point can both be used with dist_to method
        Point p(1, 1);
        cout << a.dist_to(p) << " " << p.dist_to(a) << "\n";
}