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=-1.2 required=5.0 tests=BAYES_00,FREEMAIL_FROM,
	FROM_STARTS_WITH_NUMS autolearn=no autolearn_force=no version=3.4.4
X-Received: by 10.107.40.7 with SMTP id o7mr5058993ioo.105.1518281195637;
        Sat, 10 Feb 2018 08:46:35 -0800 (PST)
X-Received: by 10.157.87.132 with SMTP id q4mr257877oth.2.1518281195359; Sat,
 10 Feb 2018 08:46:35 -0800 (PST)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!news.uzoreto.com!weretis.net!feeder6.news.weretis.net!feeder.usenetexpress.com!feeder-in1.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!w142no323838ita.0!news-out.google.com!m16ni299itm.0!nntp.google.com!o66no323311ita.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Sat, 10 Feb 2018 08:46:35 -0800 (PST)
In-Reply-To: <p5n3ap$rlh$1@dont-email.me>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=85.240.214.139;
 posting-account=rhqvKAoAAABpikMmPHJSZh4400BboHwT
NNTP-Posting-Host: 85.240.214.139
References: <5d9134c9-a7d4-468e-8685-ebbb393eabea@googlegroups.com>
 <p5kk5i$5fj$1@dont-email.me> <p5kl6u$12m5$1@gioia.aioe.org>
 <p5krq3$103$1@dont-email.me> <wcck1vlex4t.fsf@TheWorld.com>
 <p5l4nl$4hm$1@dont-email.me> <p5l60c$ol$1@gioia.aioe.org>
 <e6ab5614-74af-41e1-804c-dec1b84b449c@googlegroups.com>
 <13f51bd1-00ef-4d2a-94b9-2d2560b449f3@googlegroups.com>
 <7781f82a-7df3-4f00-9bc8-ee60c24311f6@googlegroups.com>
 <p5n3ap$rlh$1@dont-email.me>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <32ab15a8-6747-41a3-9e2d-02feb7962791@googlegroups.com>
Subject: Re: grassroots thoughts on access types
From: Mehdi Saada <00120260a@gmail.com>
Injection-Date: Sat, 10 Feb 2018 16:46:35 +0000
Content-Type: text/plain; charset="UTF-8"
Xref: reader02.eternal-september.org comp.lang.ada:50372
Date: 2018-02-10T08:46:35-08:00
List-Id: <comp.lang.ada>

>It is semantically a pointer, an object that directly references another
object.

Well, you have a point, but aren't you a bit nitpicking ?
I think one can write:

type CONTAINER_TYPE is private
      with Iterable =>  (First        => First,
                         Next         => Next
                         Has_Element  => Has_Element,
                         Element      => Get);
type CURSOR is limited private;
type ELEMENT is new WHO_CARES;
function GET(LIST: COINTAINER_TYPE, CURSOR_OBJECT: CURSOR) return ELEMENT,
function FIRST(LIST: CONTAINER_TYPE) return CURSOR;
function NEXT(LIST: CONTAINER_TYPE, CURSOR_OBJECT: CURSOR) return CURSOR;
function HAS_ELEMENT(LIST: CONTAINER_TYPE, CURSOR_OBJECT: CURSOR) return BOOLEAN;

private

type CURSOR is POSITIVE;
type CONTAINER_TYPE is ...

there isn't much difference in my understanding between this numeric CURSOR and a regular array index type. None of the usual problem of dynamic allocation, dangling pointers, unchecked this-or-that here.
So I don't really see why it should be forbidden in secure, deterministic Ada subset.