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=-2.9 required=5.0 tests=BAYES_00,MAILING_LIST_MULTI
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Google-Thread: 103376,1540032852ee6d61
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news2.google.com!news1.google.com!news3.google.com!newsfeed2.dallas1.level3.net!news.level3.com!newsfeed-00.mathworks.com!news.tele.dk!feed118.news.tele.dk!news.tele.dk!small.news.tele.dk!proxad.net!cleanfeed2-a.proxad.net!nnrp16-1.free.fr!not-for-mail
Return-Path: <Christoph.Grein@eurocopter.com>
Date: Thu, 08 Feb 2007 13:05:22 +0100
From: "Grein, Christoph (Fa. ESG)" <Christoph.Grein@eurocopter.com>
Subject: AW: Why does this work? (overloads)
In-reply-to: <1170931228.165961.8170@m58g2000cwm.googlegroups.com>
To: comp.lang.ada@ada-france.org
MIME-version: 1.0
X-MIMEOLE: Produced By Microsoft Exchange V6.5
Content-Type: text/plain; charset=iso-8859-1
Content-transfer-encoding: quoted-printable
Content-class: urn:content-classes:message
Thread-topic: Why does this work? (overloads)
Thread-index: AcdLbyVkAqt1tNCnSnS1OhG6YL1q/gACWmQg
X-OriginalArrivalTime: 08 Feb 2007 12:05:23.0972 (UTC)
	FILETIME=[69B19440:01C74B79]
X-Virus-Scanned: amavisd-new at ada-france.org
X-BeenThere: comp.lang.ada@ada-france.org
X-Mailman-Version: 2.1.9rc1
Precedence: list
List-Id: "Gateway to the comp.lang.ada Usenet newsgroup"
	<comp.lang.ada.ada-france.org>
List-Unsubscribe: <http://www.ada-france.org/mailman/listinfo/comp.lang.ada>,
	<mailto:comp.lang.ada-request@ada-france.org?subject=unsubscribe>
List-Post: <mailto:comp.lang.ada@ada-france.org>
List-Help: <mailto:comp.lang.ada-request@ada-france.org?subject=help>
List-Subscribe: <http://www.ada-france.org/mailman/listinfo/comp.lang.ada>,
	<mailto:comp.lang.ada-request@ada-france.org?subject=subscribe>
Newsgroups: comp.lang.ada
Message-ID: <mailman.84.1170936354.18371.comp.lang.ada@ada-france.org>
X-Leafnode-NNTP-Posting-Host: 88.191.17.134
Organization: Guest of ProXad - France
NNTP-Posting-Date: 08 Feb 2007 13:10:02 MET
NNTP-Posting-Host: 88.191.14.223
X-Trace: 1170936602 news-2.free.fr 30475 88.191.14.223:53062
X-Complaints-To: abuse@proxad.net
Xref: g2news2.google.com comp.lang.ada:9136
Date: 2007-02-08T13:10:02+01:00

Try this. Not very elegant, but works.

with Ada.Exceptions;

with Ada.Text_IO, Ada.Float_Text_IO;
use  Ada.Text_IO, Ada.Float_Text_IO;

with Ada.Unchecked_Conversion;

procedure Test_it is

  N: constant :=3D 10;

  type Vector is array (Integer range <>) of Float;
  -- Fat pointers don't work (include bounds).
  -- type Vector_Ptr is access all Vector;
  -- subtype Vector_Ptr_1   is Vector_Ptr (  1 .. N      );
  -- subtype Vector_Ptr_101 is Vector_Ptr (101 .. N + 100);

  -- Thin pointers (don't include bounds):
  type Vector_Ptr_1   is access all Vector (  1 .. N      );
  type Vector_Ptr_101 is access all Vector (101 .. N + 100);

  function Convert is new
    Ada.Unchecked_Conversion (Vector_Ptr_1, Vector_Ptr_101);

  X: aliased Vector (1 .. N);  -- constrained nominal subtype
  P: Vector_Ptr_1   :=3D X'Access;
  Q: Vector_Ptr_101 :=3D Convert (P);

begin

  for i in X'Range loop
    X (i) :=3D Float (i);
  end loop;

  for i in P'Range loop
    Put (Integer'Image (i));  Put (P (i));  New_Line;
  end loop;

  for i in Q'Range loop
    Put (Integer'Image (i));  Put (Q (i));  New_Line;
  end loop;

exception
  when Exc: others =3D>
    Put_Line ("Unexpected exception " &
              Ada.Exceptions.Exception_Name (Exc));

end Test_it;

-----Urspr=FCngliche Nachricht-----
Jerry wrote:

Good point. However, it uses twice the memory, and worse, changes made
in A are not reflected in B without repeating the assignment A :=3D B
(correct?) and vice versa. My Pascal trick had neither of these
problems yet carried boundary checking using either name.

Maybe there's a way to do this using unrestricted_access variables of
GNAT.

Jerry