#include "library.h"

const double twopi = 2 * acos(-1.0);

void draw_circle(const double cx, const double cy, const double r, const double alpha, const double inc)
{ if (alpha > twopi)
    return;
  const double px = cx + r * sin(alpha);
  const double py = cy - r * cos(alpha);
  if (alpha == 0)
    move_to(px, py);
  else
    draw_to(px, py);
  draw_circle(cx, cy, r, alpha + inc, inc); }

void draw_circle(const double cx, const double cy, const double r)
{ draw_circle(cx, cy, r, 0.0, 1.0 / (twopi * r)); }

void main()
{ make_window(500, 500);
  set_pen_color(color::red);
  set_pen_width(3);
  draw_circle(250, 250, 200); }