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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Strings with discriminated records
Date: Tue, 29 May 2018 09:49:18 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:52758
Date: 2018-05-29T09:49:18+02:00
List-Id: <comp.lang.ada>

On 2018-05-29 12:27 AM, Mehdi Saada wrote:
> I see, and I would expect a constant declaration M: constant nights.message := nights.create("hello world);
> to have exactly the same implementation. I am right ?

Yes. Renaming temporary objects is probably a language design bug. But 
renaming is broken in so many ways that one more, one less does not make 
much difference.

BTW, If I would allow renaming a function result, then that would have 
lazy evaluation/closure semantics.

> After all you do or not do exactly the same, as far as I understood.

There are subtle and not so subtle differences, like sliding or not 
array indices.

It is best to use rename only where it was originally intended, e.g.

1. for renaming long named objects/packages:

    X : T renames A.B.C.D.E.X;

2. for renaming view conversions:

    X : T'Class renames T'Class (Y);

3. for renaming array/list elements and record members:

    for I in A'Range loop
       declare
          Current : T renames A (I);
       begin
          ...

4. for resolving name clashes:

    type T is new Integer;
    function Integer_Add (Left, Right : Integer)
       return Integer renames "+"; -- Going to override, so keep the old
    function "+" (Left, Right : Integer)
       return Integer renames "+"; -- The new one

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de