From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ada Annoyances
Date: Tue, 27 Jun 2017 00:23:43 +0200
Organization: Aioe.org NNTP Server
Message-ID: <ois1hd$o73$1@gioia.aioe.org>
References: <1ac5a44b-4423-443a-a7bb-2864d9abe78f@googlegroups.com>
 <d6b02354-93b5-4364-9fe5-3d22b47156e9@googlegroups.com>
 <be1619b4-2220-4287-8e67-1af32377d3f7@googlegroups.com>
 <oijkah$mnh$1@franka.jacob-sparre.dk>
 <4921bd4e-3827-a7ac-7f2d-d60edbc514a3@tidorum.invalid>
 <oiphqk$osf$1@franka.jacob-sparre.dk> <erd8jiFhsroU1@mid.individual.net>
 <oirvdf$t0$1@franka.jacob-sparre.dk>
NNTP-Posting-Host: MajGvm9MbNtGBKE7r8NgYA.user.gioia.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.1
Content-Language: en-US
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:47136
Date: 2017-06-27T00:23:43+02:00
List-Id: <comp.lang.ada>

On 2017-06-26 23:47, Randy Brukardt wrote:

> There's no free lunch! T'Class is by definition "indefinite", since existing
> code already compiled has to be able to handle newly defined types
> (including those that don't yet exist). That's never going to allow
> conventional static analysis.

Indefinite unless you constrain these types is some way. Which is the 
essence of the proposal. There is nothing wrong in putting a static 
contract on T'Class upfront for all descendants to obey. After all 
abstract primitive operations is no different.

Another approach could be allowing constrained subtypes of T'Class. E.g.

    subtype S_as_T is T'Class (S);    -- Only S is allowed
    subtype T_to_S is T'Class (T..S); -- Only types between T and S

Of course to have it ane useful one need some syntax for siblings 
(breadth rather than depth).

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