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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Full view of a private partial view cannot be a subtype
Date: Mon, 18 Dec 2017 16:47:49 -0600
Organization: JSA Research & Innovation
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Xref: reader02.eternal-september.org comp.lang.ada:49525
Date: 2017-12-18T16:47:49-06:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:p16332$1rfb$1@gioia.aioe.org...
> On 2017-12-17 16:26, Jere wrote:
>
>> my assertion is that:
>>
>>     subtype Thing is Core_Pkg.Thing;
>>
>>     procedure Do_Something(The_Thing : in out Thing)
>>        renames Core_Pkg.Do_Something;
>>         is easier to both maintain and read than:
>>
>>     type Thing is new Core_Pkg.Thing with null record;
>>     procedure Do_Something(The_Thing : in out Thing);
>
> But these are two semantically different concepts. Ada's subtype declares 
> an equivalent type [it inherits everything from and exports everything to 
> the base]. Ada's new tagged type declares a new instance of a class. It 
> only inherits.
>
> I don't understand how can you exchange one for another.

You can't really; they're very different concepts. The OP is showing a 
confusion, because the renames he wants is perfectly legal, assuming proper 
visibility. And if the items in question are private, then he is trying to 
make a privacy leak -- which the language will not make easy for obvious 
reasons.

                            Randy/