Re: What's with GNAT?

[Sazonov Cyril <cyril@geol.spb.su>]

BwB wrote us:

.................
> the GNAT compiler for the SUN (sorry, I don't know the version--I'm not sure
> they do either!). But the problem seems to come from the conversion of an
> "out" parameter. The GNAT compiler says the statement wil raise
> CONTRAINT_ERROR, and if a program is executed it does indeed raise it. Since
> I am not familiar enough with GNAT, I offered to post this question for them.
..................................
> What are missing about GNAT?
..................................
>      procedure Multiply ( Left, Right : in     Global.Cartesian_Vector;
>                           Result      :    out Global.Cartesian_Vector );
..................................
>
>      procedure Multiply ( Left, Right : in     Global.NED_Vector;
>                           Result      :    out Global.NED_Vector  );
>      begin  -- Multiply
>         Multiply ( Global.Cartesian(Left), Global.Cartesian(Right),
>                    Global.NED_Vector(Result)                         );
> -------------------^^^^^^^^^^^^^^^^^^^^^^^^^
>-------------------- claims it will raise CONSTRAINT_ERROR--and does!
>      end Multiply;

I suppose you are missing about the _language_, but not _GNAT_. It seems me
that the thing is that the reurned result is of Global.Cartesian_Vector type
even though the variable Result is of Global.NED_Vector and the type
conversion is to be done _before_ assignment, perfomed by the result return.
So you are to use an intermediate variable to be able to _get_ the wanted
result and the cjnvert it. For example:

      procedure Multiply ( Left, Right : in     Global.NED_Vector;
                           Result      :    out Global.NED_Vector  );

         INTERIM : Global.Cartesian_Vector;

      begin  -- Multiply
         Multiply ( Global.Cartesian(Left), Global.Cartesian(Right),
                    INTERIM ) ;
         Result := Global.NED_Vector ( INTEGRIM ) ;
      end Multiply;

Happy New Year !

Best wishes from Russia !                             Cyril Sazonov