From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-25) on
	ip-172-31-91-241.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=0.0 required=3.0 tests=none autolearn=unavailable
	autolearn_force=no version=4.0.1
Path: nntp.eternal-september.org!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: In precision typing we trust
Date: Thu, 28 Aug 2025 09:54:11 +0200
Organization: A noiseless patient Spider
Message-ID: <108p1v3$16qn1$1@dont-email.me>
References: <107uv9g$3019a$1@dont-email.me> <107v1ji$303of$1@dont-email.me>
 <336fbb5f-a279-ea8e-67fd-f62bb00d6a89@irrt.De>
 <107vfb9$34cpj$1@dont-email.me> <mgmhbtF8u6bU1@mid.individual.net>
 <10855lq$gj8l$1@dont-email.me> <1088h1a$19635$1@dont-email.me>
 <1089p1i$1ig1d$1@dont-email.me> <108aq2p$1qo9o$1@dont-email.me>
 <b7a32260-7c15-7b63-6d39-0e5e809c7201@insomnia247.nl>
 <108dh2l$2f5h3$1@dont-email.me> <108ej11$2mbr8$1@dont-email.me>
 <108g1fv$32gqg$3@dont-email.me> <108h6b7$3a75k$3@dont-email.me>
 <87plcjn5ru.fsf@nightsong.com> <108hek3$3c6u1$1@dont-email.me>
 <87ldn7mil5.fsf@nightsong.com> <108ift9$3kh0r$1@dont-email.me>
 <108ijl2$3lihe$5@dont-email.me> <108jphl$3ti12$1@dont-email.me>
 <108liii$br9n$3@dont-email.me> <108mcoe$gv59$1@dont-email.me>
 <108o396$vok4$6@dont-email.me> <108o5hu$10c60$1@dont-email.me>
 <108o883$10pj9$4@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Thu, 28 Aug 2025 07:54:11 +0000 (UTC)
Injection-Info: dont-email.me; posting-host="6f970729dc22bef6d204ec8c3c6ab955";
	logging-data="1272545"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/b6env4Msp6lKwjsPrXd54NwPYPch3t4Q="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:QW0Sc6HqY9vEifj/FUuIlPtr23s=
In-Reply-To: <108o883$10pj9$4@dont-email.me>
Content-Language: en-US
Xref: feeder.eternal-september.org comp.lang.ada:66960
List-Id: <comp.lang.ada>

On 2025-08-28 02:35, Lawrence D’Oliveiro wrote:
> On Thu, 28 Aug 2025 01:49:18 +0200, Dmitry A. Kazakov wrote:
> 
>> On 2025-08-28 01:10, Lawrence D’Oliveiro wrote:
>>
>>> So I can do something like
>>>
>>>       function F ... is declare
>>>          type T is ...
>>>       begin
>>>          ...
>>>          return T;
>>>       end;
>>>
>>> in Ada?
>>
>> No, you cannot spell such a function. Ada is a typed language:
> 
> But I thought you said “In Ada types can be created dynamically”? So it
> turns out that’s wrong? Because I can do that in Python.

You cannot refer to a type before you created it, except specific cases 
of incomplete declarations.

In Python you cannot do that either. What you can in Python is to 
declare a function that returns nobody knows what, because Python is 
untyped.

> So you can’t actually show us any example of such a feature, to prove it
> exists? Too bad ...

I can explain how it works. When a DLL is loaded its library level gets 
elaborated. So if you have:

package P is
    type T is tagged ...
end P;

in the main program or DLL and

with P;
package Q is
    type S is new T with ...
    function F return T'Class;
end Q;

in the DLL being loaded, then in the process of elaboration S will be 
created which in particular means extending of the dispatching table. 
You can return a class-wide object from there and dispatch on the newly 
created type's operation.

Clear?

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