public void FnTest()
{
Vector2 a = (1, 1);
Vector2 b = (2, 3);
Line2 l = (a, b);
Assert.AreEqual(0, l.Fn(a));
Assert.AreEqual(0, l.Fn(b));
}
public bool CheckLeftPoint(Vector2 point) => Line.Fn(point) < 0;
public static Shape2 Mirror(this Shape2 shape, Line2 line)
{
var n = line.Normal;
return(shape.Transform(p => p - 2 * line.Fn(p) * n / line.Normal.Len2).Reverse());
}