Rectangle is defined in
is derived from
Polygon, using public derivation.
As noted above in Polygon Reference; Affine Transformations,
currently inherits its transformation functions and
operator*=(const Transform&) from
the data members of a
Rectangle, except for
not recalculated when it's transformed. I plan to change this soon! It
will also be necessary to add the function
Rectangle::is_rectangular(), in order to test whether a
Rectangle is still rectangular.