Re: How to use Annex G.3 Vectors and Matrices in bindings to C arrays

[Yves Bailly <kafka.fr@laposte.net>]

Jerry wrote:
> with arrays which are (sub)typed from the Annex G.3 declarations. For
> example, here is the declaration from the spec of
> Ada.Numerics.Generic_Real_Arrays which is GNAT file a-ngrear.ads:

Sorry for this off-topic quesiton, but which GNAT version are you using ?
I just can't find this file in GNAT-GPL...
 
>        type Real_Vector is array (Integer range <>) of Real'Base;
> (The Long_Float version, for example, is an instantiation of this
> generic and is named Ada.Numerics.Long_Real_Arrays.)
> 
> So--how do I get objects and subtypes based on the type Real_Vector to
> have aliased components or, how do I get a type that is type-compatible
> with Real_Vector but which has aliased components?
> 
> 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.

Have you tried:
type A is array(1..10) of Float;
pragma Convention(C, A);

The "pragma Convention" might be enough, at least it was when I did
some OpenGL programming in Ada, passing Ada vectors or matrices to GL
functions. It worked like a charm.

> I also wonder if it is generally possible to rationalize other bindings
> which involve connecting to C arrays by using (sub)types of the Annex
> G.3 vector and matrix types. If not, that would seem to make the Annex
> G.3 features useless whenever C array bindings are needed.

I can't try (as said, I don't have those Annex G.3-related files), but
maybe this works:
type C_Real_Vector is new Real_Vector;
pragma Convention(C, C_Real_Vector);
Though I wonder how the constraint will be handled...
 
Regards,

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