# point on circle [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 13 Exercise 12
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 13 Exercise 12

#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;
}

Point ptOnCircle(Graph_lib::Circle& c, double p) {
return Point(c.radius() * cos(M_PI * 2 * p) + c.center().x, c.radius() * sin(M_PI * 2 * p) + c.center().y);
}

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);

//Circle
Circle myCircle(center, 50);
myCircle.set_color(Color::red);
win.attach(myCircle);

//Pt on Circle
double parameter = 0;
while (true) {
Mark myMark(ptOnCircle(myCircle, parameter), ‘x’);
myMark.set_color(Color::red);
win.attach(myMark);
win.wait_for_button();
parameter += 0.1;
}
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (…) {
cout << "Exiting" << endl;
return 2;
}
[/code]