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From: "Nasser M. Abbasi" <nma@12000.org>
Newsgroups: comp.lang.ada
Subject: Re: Any easy/build-in construct to extract submatrices from larger
 matrix?
Date: Sun, 24 Jun 2012 07:16:50 -0500
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Date: 2012-06-24T07:16:50-05:00
List-Id: <comp.lang.ada>

On 6/24/2012 6:10 AM, Dmitry A. Kazakov wrote:

> And to me the problem is not clear. Are you writing a concrete program or
> considering a proper way to model matrix lattices in a strongly typed
> programming language? The difference is huge.
>
>

Dmitry;

I was try to implement, just for fun, finding the adjungate
matrix, using the direct algorithm using Ada, as shown here:

http://en.wikipedia.org/wiki/Adjugate_matrix

it requires finding the cofactors of each element in a 2D matrix.

Hence needed a simply way to obtain a submatrix from the main
matrix. I understand that slices are not supported for 2D matrices
in Ada. Only for 1D.

I think something like pack() (and unpack()) functions would be
useful to have in Ada:

http://fortranwiki.org/fortran/show/pack

pack() allows one to extract rows/columns, not necessarily
in sequence, out of a matrix using a mask matrix. This is
very useful for many linear algebra operations on matrices.

thanks,
--Nasser