Re: How to pass two dimensional arrays to C

["Björn Persson" <spam-away@nowhere.nil>]

Jerry wrote:
> I would expect that C would simply expect
> a blob of MN units of memory where each unit is the sizeof(int) and
> rely on M and N being passed as parameters to parse it up correctly.

As C, the language, has no concept of two-dimensional arrays, it can't 
expect anything at all about them. c_plmesh, the function, could have 
been written to expect this, but according to the declaration you posted 
it wasn't.

> The overall thing I have to figure out, I think, is how to convert a
> subtype of Long_Float_Array_2D such as PL_Float_Array_2D into an array
> of pointers.

I think something like this should work:

procedure PLmesh
   (x   : PL_Float_Array;
    y   : PL_Float_Array;
    z   : PL_Float_Array_2D;
    opt : PLINT)
is
    Pointer_Array : PLFLT_Ptr_Array(z'Range(1));
begin
    for Index in z'Range(1) loop
       Pointer_Array(Index) := z(Index, 1)'Access;
    end loop;
    c_plmesh(x, y, Pointer_Array, z'Length(1), z'Length(2), opt);
end PLmesh;

That's just to show the idea. Be sure to check the details carefully, 
especially in what order the elements of z are stored.

-- 
Bj�rn Persson                              PGP key A88682FD
                    omb jor ers @sv ge.
                    r o.b n.p son eri nu