# regular polygon class [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 13 Exercise 10
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```
```//  Philipp Siedler
//  Bjarne Stroustrup's PP
//  Chapter 13 Exercise 10

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>

using namespace Graph_lib;

ostream& operator<<(ostream& out, Point& a) {
out << "(" << a.x << "," << a.y << ")";
return out;
}

struct Regular_polygon : Closed_polyline
{
Regular_polygon(Point origin, int radius, int segments, Fl_Color linecolor)
{
s = (s < 3) ? segments : 3;
generate_points();
};
Regular_polygon(Point origin, int radius, int segments)
{
s = (s < 3) ? segments : 3;
generate_points();
};

void generate_points();
void draw_lines() const;

private:
Point o;
int r;
int s;
Fl_Color lc;
};

void Regular_polygon::generate_points()
{
for (int i = 1; i < s + 1; i++) {
add(Point(r * sin(((2 * M_PI) / s) * i) + o.x, r * cos(((2 * M_PI) / s) * i) + o.y));
}
};

void Regular_polygon::draw_lines() const
{
fl_color(lc);
Closed_polyline::draw_lines();
};

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, 720, 400, "Simple Window");
Point center(win.x_max() / 2, win.y_max() / 2);

Regular_polygon h(center, 50, 8, FL_RED);

win.attach(h);
win.wait_for_button();
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (...) {
cout << "Exiting" << endl;
return 2;
}
```

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