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Re: Non-commutative symbolic multiplication in Calc


From: Neon Absentius
Subject: Re: Non-commutative symbolic multiplication in Calc
Date: Tue, 6 Sep 2005 19:12:48 +0000
User-agent: Mutt/1.4.2.1i

On Tue, Sep 06, 2005 at 08:36:49PM +0200, Roland Winkler wrote:
> Neon Absentius <address@hidden> writes:
> > Ideally the multiplication should not be assumed commutative (or the
> > variables invertible) unless explicitly declared so.
> 
> Emacs calc (the way I look at it) is designed to be a powerful,
> advanced calculator. But it is not a computer algebra system which I
> would use to address the kind of problem you are talking about..
> 

If there is a line between an advanced desk calculator and a CAS then
surely Emacs calc has crossed it! OTOH what are PC's but (glorified)
advanced desk calculators? :)

But (more) seriously what I am talking about is not really that more 
complicated than what calc does already. If it can calculate 
          2     2            2
   (x + y)   = x  + 2 y x + y

then it should be able to do 
          2     2                2
   (x + y)   = x  + x y + y x + y
   

> For example. take a look at Maxima, http://www.ma.utexas.edu/maxima.html.
> It's now under GPL, and it even has a nice emacs interface.

Yes I know about maxima and I use it. However I usually prefer calc
for a "quick and dirty" calculation. And I really like the interface.


-- 
Most precious among the relics remaining of Peter's skeleton in the
Vatican are 29 fragments of one of his skulls. (St. Peter's other
skull is preserved in a reliquary at the Cathedral of St. John
Lateran.)
   -- Frank R. Zindler, "Of Bones and Boners"




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