Re: Circles and ellipses

>If a single point
>can be construed as two coincident foci,
>than why can't two rows of a table have the same values, in all of the
>columns, and still be two elements of the
>relation the table is supposed to represent?

Within an ellipse variable, each focus is a separate variable with its own identity. Two relation variables can each have one or more rows whose value is identical to a corresponding row in the other relation variable. However, if two rows in a relation have the same value, they cease to have separate identities and become the same variable.

>But let's return to cicle/ellipse for a minute? Why would anyone WANT to
>consider a circle an ellipse?
>Well, I can see one immediate benefit: if
>all the relevant operations that work on an ellipse also work on a circle,
>then you can get more useful software written by construing a cirlce as a
>specialized ellipse, and not writing an implementation for a whole
>different class.
>
>That, to me, is more to the point than the underlying math.

Agreed. Received on Sun Aug 19 2001 - 08:16:04 CEST