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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: ADA.STRINGS.INDEX_ERROR : a-strunb.adb:782
Date: Thu, 18 Jan 2018 09:34:48 +0100
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Xref: reader02.eternal-september.org comp.lang.ada:49970
Date: 2018-01-18T09:34:48+01:00
List-Id: <comp.lang.ada>

On 17/01/2018 23:50, Mehdi Saada wrote:
>> Remember position vs. index:
>>      Length : constant Integer := Object'Length;
>>      First  : constant Index_Type := Object'First;
>>      Last   : constant Index_Type := Object'Last;
> 
> Yeah, an Integer subtype. Ah, always something I forget to precise explicitely.
> I saw it goes along well with a constant declaration, but I wanted a renaming declaration...

You can rename result of a function too. (It does make much sense in the 
case of scalar values returned by value).

However you cannot rename a non-object. A subtle distinction, but it is 
there. That would prevent renaming of an attribute Object'Length which 
is not an object for whatever strange reason. Attributes have a long 
history of being queer. E.g. "abc"'Length is still illegal, AFAIK. In 
Ada attributes are not considered operations as they should.

A discriminant of some object can be renamed, no problem. So

    type Object_Type (Length : Natural) is ...;
    Object : Object_Type (10);
    Length : Integer renames Object.Length; -- This is OK, 10

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