Re: Will "renames" increase program size?

[AdaMagica <christ-usch.grein@t-online.de>]

On 15 Jun., 15:15, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> On Wed, 15 Jun 2011 13:24:52 +0200, Yannick Duchêne (Hibou57) wrote:
> > Le Wed, 15 Jun 2011 07:37:22 +0200, Randy Brukardt <ra...@rrsoftware.com>  
> > a écrit:
> >> Some examples where there probably would be some overhead:
>
> >>              Obj : Natural renames My_Array (Some_Variable).all;
> >>              Obj2 : Float renames Some_Function (A, B);
>
> > Yes, because this is more an aliasing (in the symbolic sense) than a  
> > proper renaming.
>
> Yes, Ada's renaming is not renaming. Consider this:
>
>    Line : String renames Get_Line;
>
> It calls Get_Line once and keeps the result object. In fact it is an
> equivalent to:
>
>    <anonymous> : constant String := Get_Line;
>    Line : properly renames <anonymous>;
>
> Consider also the effect of renaming on the visibility rules:
>
>    package P1 is
>       End_Error : exception renames Ada.Text_IO.End_Error;
>    end P1;
>    package P2 is
>       End_Error : exception renames Ada.Text_IO.End_Error;
>    end P2;
>    use P1, P2;
>
>    exception
>       when End_Error => -- End_Error is hidden!
>
> Ada's "renames" does not rename here, it copies, creates objects. There are
> three End_Error here, all of them are equal, but not same:
>
> exception
>    when Ada.Text_IO.End_Error =>
>       ...
>    when P1.End_Error => -- Error! P1.End_Error has the same value
>       ...
>    when P2.End_Error =>
>       ...
>
> A proper renaming would create identical (x≡y) entities, Ada's renaming
> sometimes creates only equal ones (x=y).
>
> --
> Regards,
> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de

That's not correct. A renaming does not copy nor somehow create new
entities, it only creates new names for the same thing. Since
visibility is via names, you arrive at unresolvability issues.