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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: Mon, 25 Jun 2012 23:19:29 -0500
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Date: 2012-06-25T23:19:29-05:00
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On 6/25/2012 9:48 PM, Jerry wrote:
>
> The reverse operation, composition, is also useful. In Matlab/Octave
> (assuming compatible sizes):
> C = [A, B] makes A B
> and
> D = [A; B] makes
>    A
>    B
> and
> [0, 0, 0, A; B, 0, 0, 0] makes
>     0   0   0   A
>     B   0   0   0
> etc.
>

If you are interested in comparing specifically matrix/vector
operations, I have a specific note in my HOWTO cheat sheet
just for this topic, it is at node 66:

http://12000.org/my_notes/mma_matlab_control/KERNEL/node66.htm

side-by-side comparison. I have Matlab, Mathematica, and
started to add Fortran. Might add Ada later on, but I am
not good in Ada to do that yet. I am not even good in Fortran
but I added few examples just to compare the ease).

Matlab and Mathematica do make working with matrices
and vectors very easy. Since the syntax and functions that are
build into them makes it so. They are designed for this
type of work. In Mathematica one uses patterns and many build-in
functions to do that, while in Matlab it is mostly the nice
build-in syntax designed for matrix work.

> Which brings me to one of my least favorite Ada features, the use of
> () instead of [] for array indices. Talk about a readability killer.

Yes. I would have preferred [] for arrays. But this was talked
about before many times. The view is that array access can be
looked at mathematically as also a function call.

When one writes A(3), then this is also a function call that
takes 3 as its argument and returns the value at that location.

But I myself would prefer [] for indexing and () for 'actual'
function call, just so that when I am reading code, [] will
remind me I am looking at an array not a function.

But too late for Ada to do this change. Already baked in. It
is interesting that in Pascal one uses [] for arrays and Ada
was based on Pascal. But the original designers for Ada for
some reason did not follow Pascal here. too bad.

> But I'm sure that's been beat to death many times. (No, it's not
> because [] are not part of ASCII.)
>
> Jerry
>

--Nasser