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Date: Sat, 03 Feb 2007 18:48:52 +0100
From: Gautier <gautier@fakeaddress.nil>
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Subject: Re: C Interface example
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Date: 2007-02-03T18:48:52+01:00
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artifact.one@googlemail.com:

> I'm having a bit of trouble getting my head around calling C code
> in Ada. I'll spare you my failed attempts, basically I have this code:
> 
> (vector.h)
> 
> #ifndef VECTOR_H
> #define VECTOR_H
> 
> float *vec_addNf(float *, float *, unsigned int);
> 
> #endif
> 
> (vec_add.c)
> 
> #include "vector.h"
> 
> 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.

Looking at your code the most simple and portable way will be not to interface 
at all with C!

package Vectors is

   type Vector is array(Natural range <>) of Float;

   procedure Add(va: in out Vector; vb: in Vector);

end Vectors;

package body Vectors is

   procedure Add(va: in out Vector; vb: in Vector) is
   begin
     for i in va'Range loop
       va(i):= va(i) + vb(i);
     end loop;
   end Add;

end Vectors;

Note that most compilers accept the spec and the body (or more!) in the same 
file with the name of your choice; GNAT requires vectors.ads and vectors.adb
HTH
______________________________________________________________
Gautier         -- http://www.mysunrise.ch/users/gdm/index.htm
Ada programming -- http://www.mysunrise.ch/users/gdm/gsoft.htm

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