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!feeder.eternal-september.org!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: stopping a loop iteration without exiting it
Date: Sun, 7 Jan 2018 13:52:31 +0200
Organization: Tidorum Ltd
Message-ID: <fbeg00F9jdlU1@mid.individual.net>
References: <bc57c2d8-ed05-4e8b-b7db-440984976364@googlegroups.com>
 <81971548-23c9-4927-a6a8-6f0f1dba896b@googlegroups.com>
 <p2jhdl$da4$1@franka.jacob-sparre.dk> <wccr2r6ttuh.fsf@TheWorld.com>
 <p2kufi$f1l$1@dont-email.me> <p2l1kr$11p4$1@gioia.aioe.org>
 <wccd12p4das.fsf@TheWorld.com> <p2m5m0$16p3$1@gioia.aioe.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: individual.net gpzAKfaWx6MYTeucqfQqFgXUnAc+FX1fk29ypFcbbTl5AeGfwv
Cancel-Lock: sha1:pTPT2QwpP3+YlCMrEUEIELkVLkY=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:45.0)
 Gecko/20100101 Thunderbird/45.8.0
In-Reply-To: <p2m5m0$16p3$1@gioia.aioe.org>
Xref: reader02.eternal-september.org comp.lang.ada:49801
Date: 2018-01-07T13:52:31+02:00
List-Id: <comp.lang.ada>

On 18-01-04 23:17 , Dmitry A. Kazakov wrote:

> I thought about really important cases, but could not invent syntax:
>
>    if X in T'Class then
>       declare
>          Same_X : T'Class renames T'Class (X);
>       begin
>          ...
>       end;
>    end if;

I suggested and we discussed a form of "case" statement as new syntax 
for this. Here is another syntax suggestion using the keyword "is" to 
form a new kind of membership test, which also assigns a new name to the 
object when the test succeeds:

    if X is Same_X : T'Class then
       ...
    end if;

Another form, retaining the "in", could be

    if X is Same_X in T'Class then
       ...
    end if;

>    if P /= null then
>       declare
>          X : P_Type renames P.all;
>       begin
>          ...
>       end;
>    end if;

    if P.all is X : P_Type then
       ...
    end if;

where there would have to be a rule that the membership test is false if 
P is null, without raising Constraint_Error.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .