Hi Michael,
Thank you very much for your corrections. I'll try it out later today.

As far as your updating modifying addObject(), that is your area of expertise.
I lack a lot of understanding, but have vague concerns about some adverse side effects.
For example, if I were "stick framing" a tetrahedron with duplicate edges for the 4 triangular sides, would
it no longer be possible to have two lines on top of each other?

- Brian