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Date: Sat, 30 Jun 2007 13:52:22 +0200
From: Georg Bauhaus <bauhaus.rm.tsoh@maps.futureapps.de>
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Newsgroups: comp.lang.ada
Subject: Re: Bus error
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Date: 2007-06-30T13:48:58+02:00
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Dmitry A. Kazakov wrote:
> On Fri, 29 Jun 2007 21:37:43 -0400, Robert A Duff wrote:

> If you have
> 
>    X1 : String renames Get_Line;
>    X2 : String renames Get_Line;
>    X3 : String renames Get_Line;
> 
> the effect will be X1, X2, X3 all different objects. This should not be
> called renaming.
 

There happen to be no explicit arguments in the function calls.
Does the same reasoning apply to

    X1 : String renames Get_Line(Foo);
    X2 : String renames Get_Line(Bar);
    X3 : String renames Get_Line(Baz, Mode => Frobnicate);


> But when I do:
> 
>    X : Element renames Collection (Key);
> 
> I'd like to be certain that X indeed renames a container's element.

Then I think there is a problem of choosing the right name for
what you have called Collection here. Ada not being a declarative
language, and if Collection is a function, then the name of the
function should probably indicate what the function *does* if and
when you do care about how it achieves some purpose.
Something like Get_From_Collection(Key) seems more likely a good
name in this case.

I'd agree that there is a "reading level ambiguity" in

   X : Data_Type renames Fun_Call_Result;
and
   X : Fun_Decl renames Another_Fun;


> package My_IO is
>    ...
>    with new Ada.Text_IO.Integer_IO (...);
>       -- Merge all declarations from this instance with My_Io's public
>       -- and private parts

Which IMHO defeats the purpose of well designed packages: focus on one
thing. (A two dozen years old package like Text_IO formed around various
assumptions might serve to construct an exception.)
Why not use interfaces when you need to lump things together? Do you have
a few convincing examples that show how the decoupling of modules should
be "improved" with a mechanism of merging them into one? (That is, of
importing and reexporting declarations of entire packages.)