gistfile1.txt

  void drawEighthOfCircle( int radius ) {
	int y = radius;
	int x = 0;

	// invariant: radius^2 <= x^2 + y^2 < (radius+1)^2
	int maxLength = (radius+1)*(radius+1);
	while( x <= y ) {
		setPixel( x, y );

		x++;
		if( x*x + y*y >= maxLength ) {
			y--;
		}
	}
}