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From: Georg Bauhaus <sb463ba@d2-hrz.uni-duisburg.de>
Newsgroups: comp.lang.ada
Subject: Re: Slice from a matrix?
Date: Fri, 23 May 2003 18:13:26 +0000 (UTC)
Organization: GMUGHDU
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David C. Hoos <david.c.hoos.sr@ada95.com> wrote:
: "Harald Schmidt" <harald.schmidt@anobject.net> wrote in message
:>   [...]
:> Package matrix is
:>     type vector_type is array (positive range <>) of item_type;
:>     type matrix_type is array (positive range <>,
:>                                positive range <>) of item_type;
:>     subtype col_vector is vector_type(1..cols);
:>     subtype row_vector is vector_type(1..rows);
:>     subtype matrix is matrix_type(1..rows, 1..cols);
:> ...
:> End matrix;
:> My question is how to get a slice from a matrix which I can convert to a
:> col_vector which does the printing?
:>

: Since slices in ada can only be taken from one-dimensional arrays, you
: would need to declare your matrix as an array of vectors.
: Individual elements are then accessed by matrix (m}{n}.

Wouldn't this be a good opportunity to hide the implementation of
both vector_type and matrix_type, declare the needed subprograms
in the matrix spec, and use whatever combination of data "layout"
and algorithms seem appropriate to implement access to columns,
rows, and cells?