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From: Yves Bailly <kafka.fr@laposte.net>
Subject: Re: How to use Annex G.3 Vectors and Matrices in bindings to C arrays
Newsgroups: comp.lang.ada
Date: Mon, 13 Nov 2006 18:42:56 +0100
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Date: 2006-11-13T18:44:10+01:00
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Jerry wrote:

> Jeffrey R. Carter wrote:
>> Jerry wrote:
>> >
>> > I wonder if I am incorrect in believing that the binding to C-arrays
>> > need aliased components. Like I said, the reason for that is a little
>> > fuzzy to me right now. But I do know that if I remove the aliased
>> > component requirement from Long_Float_Array_1D the binding will not
>> > compile.
>>
>> What is the error message that you get? Are you taking 'access of
>> components of such arrays?
>>
> I'm afraid I'll have to apologize for not being accurate in my initial
> post. Indeed, I am not having any problems (as I erroneously claimed)
> with 1D arrays. The problem arises with 2D arrays, about which I
> pestered the list earlier. With further apologies for posting a bit
> more code that I would like, the following is a typical binding that I
> made in which it was necessary to gain access to 2D C arrays.

As far as I know, nD arrays (n > 1) in Ada are very different things than
nD arrays in C. Basically, a 2D array in C is an array of arrays, but this
is not the case in Ada (it *might* be the case, but I guess it's compiler-
dependant).

So I'm not sure if it's actually possible to correctly pass nD arrays to
C code... Back again to my OpenGL code, I did things like this:
type Vector is array(1..3) of Float;
pragma Convention(C, Vector);
type Matrix is array(1..3) of Vector;
pragma Convention(C, Matrix);
...and it worked quite well.

But maybe this pragma works for nD arrays? I'm quite interested in the
answer (I'll test this as soon as I have some time).

Regards,

-- 
(o< | Yves Bailly  : http://kafka-fr.net   | -o)
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