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,FREEMAIL_FROM
	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!mx05.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Generic access type convention and aliasing
Date: Tue, 07 May 2013 21:08:48 +0200
Organization: Ada @ Home
Message-ID: <op.wwp94yh5ule2fv@cardamome>
References: <op.wwmy7p00ule2fv@cardamome> <op.wwneq7xtule2fv@cardamome>
 <km9jg4$eue$1@munin.nbi.dk> <op.wwo9q8s2ule2fv@cardamome>
 <5a96b4f0-15d3-4fe2-9e9c-000f59b9c864@googlegroups.com>
NNTP-Posting-Host: /5uFWkegPs0CGJSoRIUiIw.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes
Content-Transfer-Encoding: Quoted-Printable
X-Complaints-To: abuse@aioe.org
User-Agent: Opera Mail/12.15 (Linux)
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:15405
Date: 2013-05-07T21:08:48+02:00
List-Id: <comp.lang.ada>

Le Tue, 07 May 2013 19:34:58 +0200, AdaMagica  =

<christ-usch.grein@t-online.de> a =C3=A9crit:
>
> This is not an access discriminant:

Oops someone flagged=E2=80=A6, yes, sorry, I made multiple tests and did=
 not  =

notice when I posted (only later and too late).

>
> Access disciminants are uncopiable.

If so, that's *very easily defeated*:


     procedure Foo is

        package Storages is

           type Element_Type is new Integer;

           type Instance_Type
             (Element : access Element_Type :=3D null) is
              limited
              private;

           function Create
              return Instance_Type;

        private

           I : aliased Element_Type;

           type Instance_Type
             (Element : access Element_Type :=3D null) is
              null record;

           function Create
              return Instance_Type
              is (Instance_Type'(Element =3D> I'Access));

        end Storages;

        type Pool_Specific_Access is access Storages.Element_Type;
        type General_Access is access all Storages.Element_Type;

        S  : Storages.Instance_Type  :=3D Storages.Create;
        A1 : Pool_Specific_Access :=3D S.Element; -- Illegal.
        A2 : access Storages.Element_Type :=3D S.Element; -- However sti=
ll  =

legal.
        A3 : General_Access :=3D S.Element; -- And the same.

     begin -- Foo

        A2.all :=3D 2;

     end Foo;


Far from what limited access type would be.


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity