Re: Non-commutative symbolic multiplication in Calc

[Neon Absentius <absent@sdf.lonestar.org>]

On Tue, Sep 06, 2005 at 04:09:36PM +0200, Roland Winkler wrote:
> Neon Absentius <absent@sdf.lonestar.org> writes:
> 
> > Sorry if this is not the right list for this question. 
> >
> > Is there a way to suspend some of the automatic simplifications that
> > calc performs? In particular I am interested in suspending the
> > assumption that multiplication is commutative.  This would allow for 
> > symbolic calculations with entities that are not necessarily numbers
> > or elements of some vector space.   
> 
> It's a pretty tricky issue to get useful results when doing
> analytical calculations with noncommuting variables. 

It seems to me that is tricky to get useful results when doing any
calculations! In any case I am mostly interested in algebraic rather
than analytic results.
 
> I doubt that you will get what you want when you just remove the
> assumption that multiplication is commutative.

Depends on what do you mean by "just" by "remove" and by
"assumption".  When I say "suspend the assumption" I mean
(obviously) to also suspend its consequences, for example there
should be a "left" and a "right" division. It depends also on what I
want, which (at the moment of writing at least) is rather modest, I
will be happy if I am able to work on a free group (or a tensor
algebra) and define relations as rewrite rules.

Ideally the multiplication should not be assumed commutative (or the
variables invertible) unless explicitly declared so.

> 
> Roland

-- 
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