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Re: Bug in Calc?
From: |
Jay Belanger |
Subject: |
Re: Bug in Calc? |
Date: |
Wed, 07 Sep 2005 08:56:37 -0500 |
User-agent: |
Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux) |
Neon Absentius <absent@sdf.lonestar.org> writes:
> On Tue, Sep 06, 2005 at 09:33:48PM +0000, Neon Absentius wrote:
>
>> there seems to be a bug: After I give 'm v' if I ask calc to
>> simplify the expression 'a b - b a' it leaves it as is which is as
>> expected. However when I ask it to expand '(a+b)^2' it returns
>> 'a^2 + 2 b a + b^2' which is of course wrong if a and b don't commute.
>> This happens both with emacs-multi-tty (22.0.50) and whith emacs
>> 21.4.1 on a Debian testing/unstable. The bug manifsts itself also
>> for the expansion of '(a+b)^3' however calc expands '(x+y)(x-y)'
>> into 'x^2 + y x - x y + y^2'. Strange!
>
> Maybe not so strange.
Maybe not strange, but still a bug.
> Probably calc uses formulae (the binomial expansion?) to expand the
> power instead of fully distributing the multiplication over the
> addtition "by hand", so to speak. Of course the binomial expansion
> is not valid if the variables involved do not commute.
That is what happens. It should be fixed soon.
Jay