At 9:57 PM -0700 1/4/07, Doug McNutt wrote:
At 18:23 -0800 1/4/07, Dave Whipp wrote:
Darren Duncan wrote:

For example, the extra space of putting them aside will let us expand them to make them more thorough, such as dealing well with exact vs inexact, fixed vs infinite length, fuzzy or interval based vs not, caring about sigfigs or not, real vs complex vs quaternon, etc.

>I agree with the general idea that this is non core (from an implementatin perspective); but one thing struck me here (slightly off topic, but not too far): a quaternion cannot be a Num because anyone using a "Num" will assume that multiplication is commutative (for quaternions, $a*$b != $b*$a).

Quaternions are much more like vectors - real ones - where we have been before.

Vectors, matrices, tensors, and symmetry groups should not be core but the procedures for overloading operators so that they can be implemented as add-ins should be ready to use and easy for a simple-minded mathematician to implement.

FYI, my mentioning of quaternions was a throwaway example, based on the assumption from context that they were to complex what complex was to real; please ignore that detail in my post. -- Darren Duncan

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