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From: Vinzent Hoefler <ada.rocks@jlfencey.com>
Newsgroups: comp.lang.ada
Subject: Re: Is ther any sense in *= and matrices?
Date: Thu, 05 Jun 2003 18:38:37 +0200
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Date: 2003-06-05T18:38:37+02:00
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Preben Randhol wrote:

>Vinzent Hoefler wrote:
>> Preben Randhol wrote:
>>=20
>>>Vinzent Hoefler wrote:
>>>> Of course it is. But because you have to write the Multiply function
>>>> yourself anyway and such can take care of that issue, I don't see =
why
>>>> this should be a problem.=20
>>>
>>>Because it doesn't make sense mathematically.
>>=20
>> Dividing by zero doesn't make sense either. So IMO that's what the
>> Constraint_Error is for.
>
>The Contraint_Error here is for that *=3D would return a C (m x n) which
>differes from the A (n x n).

Ok, understood.

Depends on how you look at it:

Let's take an extreme example and suppose I have an integer type
defined only for range 0 .. 1. So writing a +=3D would only make sense
for the "special" case that at least one of the operands is zero, not
for the general case, because then the result doesn't fit into the
original operand. But I wouldn't say, writing such a function wouldn't
make sense at all... ;)

In the matrix case it's just that you can't write a *=3D that works for
the more general case. Simple as that. I really wouldn't see a problem
with that.

>So *=3D is only usefule (/=3D too) in special
>cases such as square matrix.

Yes.

>Therefore you must make a function Prod
>(A,B) at any rate and the *=3D will be of no use as Prod (A,B) is
>general.

No, maybe you want to multiply square matrices only? ;)


Vinzent.

--=20
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