From: Neon Absentius <absent@sdf.lonestar.org>
Subject: Re: Non-Commutative calculations in Calc, Revisited
Date: Thu, 6 Oct 2005 18:01:13 +0000 [thread overview]
Message-ID: <20051006180113.GA24696@SDF.LONESTAR.ORG> (raw)
In-Reply-To: <851x2yu5gv.fsf@lola.goethe.zz>
On Thu, Oct 06, 2005 at 03:42:40PM +0200, David Kastrup wrote:
> Jay Belanger <belanger@truman.edu> writes:
>
> > Neon Absentius <absent@sdf.lonestar.org> writes:
> >
> >> When in non-commutative (aka `matrix') mode calc calculates
> >> (a b)^-1 to be a^-1 b^-1 instead of the correct b^-1 a^-1.
>
> Uh, what's correct about b^-1 a^-1?
>
> Set a=[1,1], b=[1;0], then (a b)^-1 = [1], and neither b^-1 nor a^-1
> exist.
>
> This only works with a and b being square matrices.
Yes you are right.
However I am more interested in the case that there is a *globally*
defined associative multiplication and I am using the matrix mode as a
"poor man's no-commutative algebra mode". In this context my remark
makes sence. I still believe that there is a need for such a mode,
perhaps a "sub-mode" of the matrix mode where one assumes that all
matrices are square. I am not sure how hard this is to implement.
What do you think Jay?
--
Everyone is so overwhelmed by the hospitality. And so many of the
people in the arena here, you know, were underprivileged anyway, so
this--this (she chuckles slightly) is working very well for them.
-- Barbara Bush, about the refugees from New Orleans.
next prev parent reply other threads:[~2005-10-06 18:01 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.9745.1128461080.20277.help-gnu-emacs@gnu.org>
2005-10-06 13:16 ` Non-Commutative calculations in Calc, Revisited Jay Belanger
2005-10-06 13:42 ` David Kastrup
2005-10-06 16:17 ` Jay Belanger
2005-10-06 18:23 ` Neon Absentius
2005-10-06 18:01 ` Neon Absentius [this message]
2005-10-07 0:47 ` Neon Absentius
[not found] ` <mailman.10168.1128646105.20277.help-gnu-emacs@gnu.org>
[not found] ` <wi7jcqt9ep.fsf@dms.auburn.edu>
2005-10-07 2:15 ` Neon Absentius
[not found] ` <mailman.10178.1128651397.20277.help-gnu-emacs@gnu.org>
2005-10-07 7:26 ` David Kastrup
[not found] ` <mailman.10119.1128621714.20277.help-gnu-emacs@gnu.org>
2005-10-07 3:59 ` Jay Belanger
2005-10-07 21:31 ` Jay Belanger
2005-10-04 21:23 Neon Absentius
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