Re: [MATHEDCC] Real world and negatives

Kirby Urner (urner@alumni.Princeton.EDU)
Tue, 16 Nov 1999 17:16:27 GMT

>The difference between the two directions is now
>handled by placement. Different notation. You
>can keep the negative sign as an operator though,
>why not? IE:
>
> (0,3) =3D (0,-3) =3D -(3,0)

>
> (0,3) =3D (0,-3) =3D -(3,0)
>

Ah, I see I flubbed it. Silly me.

(0,3) =3D (-3,0) =3D -(3,0)

would have been correct.

Apologies.=20

Kirby

PS: Note that in the full-blown quadrays system,
we do have the option to normalize such that the
sum of the coordinates always adds to zero. This
brings quadrays closer to what's already in the=20
literature under the heading of "simplicial=20
coordinates" (not the same as barycentrics).
However, the 4-tuples are usually read as talking
about some 4-dimensional (trans 3-d) shape, whereas
the interpretation given at my website is strictly
about ordinary volume (so-called Euclidean space).

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