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!.POSTED!not-for-mail
From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Q: discrete_subtype_definition: static only cases?
Date: Sun, 7 Jun 2020 15:02:54 +0200
Organization: Also freenews.netfront.net; news.tornevall.net;
 news.eternal-september.org
Message-ID: <rbiohu$f9m$2@dont-email.me>
References: <2d4d6645-7055-4564-a854-6da5fc83af4eo@googlegroups.com>
 <rbig69$jg8$1@dont-email.me>
 <9c45012c-a4b5-416d-bf1e-c2a8479ec641o@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Sun, 7 Jun 2020 13:02:54 -0000 (UTC)
Injection-Info: reader02.eternal-september.org;
 posting-host="b243c502e7d88efa94d0bed85751046f";
	logging-data="15670"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX18PjAh55Q7ak5avm8ixgtle1tE1A92s26k="
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.8.0
Cancel-Lock: sha1:78UzwSqlWowDzAdBbQpUm4d4nTU=
In-Reply-To: <9c45012c-a4b5-416d-bf1e-c2a8479ec641o@googlegroups.com>
Content-Language: en-US
Xref: reader01.eternal-september.org comp.lang.ada:59003
Date: 2020-06-07T15:02:54+02:00
List-Id: <comp.lang.ada>

On 6/7/20 2:13 PM, gautier_niouzes@hotmail.com wrote:
>> No. The basic principle is that types are static (they determine the
>> underlying representation) and subtypes are dynamic.
> 
> Well, there are obviously exceptions to that basic principle:
> 
> procedure SD2 is
> begin
>    for I in 1 .. 3 loop
>      declare
>        type T is array (1 .. I) of Integer;  --  I is a variable
>        B: T;
>      begin
>        null;
>      end;
>    end loop;
> end;

Conceptually, this declaration is equivalent to

type /anon/ is array (Integer range <>) of Integer;
subtype T is /anon/ (1 .. I);

So the (anonymous) type is static, but the (first-named) subtype is not.

-- 
Jeff Carter
"How'd you like to hide the egg and gurgitate
a few saucers of mocha java?"
Never Give a Sucker an Even Break
101