// cool highlighting!
$f = fopen(source, "rb");
while(!eof($f)) {
  $s = fgets($f);
  $h = parse($s);
  echo $h;
}

// slow integer factorial function
int factorial(int n)
{
  int r = 1;
  while(n > 1) {
    r *= n;
    --n;
  }
  return r;
}

void Image::DrawCircle(float x, float y, float radius)
{
  // TODO: add tests to prevent computing all the points for nothing
  //       (i.e. determine whether any part of the circle is visible
  //       in the output image)
  if(radius <= 0.0f) {
    return;
  }
  float circumference = 2.0f * M_PI * radius;
  if(circumference < 1.0f) {
    circumference = 1.0f;
  }
  for(float p = 0.0f; p < circumference; p += 0.5f) {
    float alpha = 2.0f * M_PI * p / circumference;
    float px = x + cos(alpha) * radius;
    float py = y + sin(alpha) * radius;
    // DrawPoint takes care of the smoothing for us
    // If thickness != 1 then we should draw lines instead!
    DrawPoint(px, py);
  }
}