Subclass sadness (was Re: [Python-Dev] PEP 285: Adding a bool type)

[Arthur Siegel]

>What is the circle-ellipse problem

In my PyGeo implementation, circle is a sub-class
of plane.

And a circle represents in effect all geometric
objects projectively equivalent to a circle - the 
ellipse, hyperbola, and parabola - which are
drawn by projecting a circle from a point 
in space to a plane in space.

All of which follows concepts of a geometry that
can be considered a *root* geometry - generalized
projective geometry.

The programming point may be that only when
working from authentically root concepts 
can sub-classing be sound.

Art