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From: "Jeffrey R. Carter" <jrcarter@acm.org>
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Subject: Re: C Interface example
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artifact.one@googlemail.com wrote:
> float *vec_add(float *va, float *vb, unsigned int ne)
> {
>   unsigned int ind;
>   for (ind = 0; ind < ne; ++ind)
>     va[ind] += vb[ind];
>   return va;
> }
> 
> Now what would be the most simple and portable way to write
> a vector,ads and vector.adb file? (Specification and body, in case
> those are compiler-specific filenames, I'm not intimate with the
> Ada language spec yet!). I just don't have a good enough
> understanding of the language to see how it all fits together
> yet and I usually learn by example.

I think all of the examples posted so far have some minor problem or 
other in meeting your goal of portability. I'd suggest

with Interfaces.C;
package C_Vectors is
    type Vector is array (Positive range <>) of Interfaces.C.C_Float;
    pragma Convention (C, Vector);

    procedure Add
       (To : in out Vector; Using : in Vector; Length : in Natural);
end C_Vectors;

package body C_Vectors is
    procedure Add
       (To : in out Vector; Using : in Vector; Length : in Natural)
    is
       type C_Ptr is access all Interfaces.C.C_Float;
       pragma Convention (C, C_Ptr);

       function C_Add
          (To : Vector; Using : Vector: Length : Interfaces.C.Unsigned)
       return C_Ptr;
       pragma Import (C, C_Add, "vec_addNf");

       Result : C_Ptr;
    begin -- Add
       Result := C_Add (To, Using, Interfaces.C.Unsigned (Length) );
    end Add;
end C_Vectors;

-- 
Jeff Carter
"C++ is like jamming a helicopter inside a Miata
and expecting some sort of improvement."
Drew Olbrich
51