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=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD,
	FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: a07f3367d7,e276c1ed16429c03
X-Google-Attributes: gida07f3367d7,public,usenet
X-Google-NewGroupId: yes
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!postnews.google.com!u10g2000yqk.googlegroups.com!not-for-mail
From: ramon_garcia <ramon.garcia.f@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada is getting more popular!
Date: Wed, 13 Oct 2010 14:53:14 -0700 (PDT)
Organization: http://groups.google.com
Message-ID: 
 <020ea727-e8e9-4d0d-8c5f-b8ad907fc3c9@u10g2000yqk.googlegroups.com>
References: <i93mac$73v$1@speranza.aioe.org>
 <bbe0c03c-6afd-40de-bf9e-04aa04b53504@n7g2000vbo.googlegroups.com>
 <i94sak$47q$1@tornado.tornevall.net>
NNTP-Posting-Host: 88.84.91.37
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
X-Trace: posting.google.com 1287006800 22123 127.0.0.1 (13 Oct 2010 21:53:20
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Wed, 13 Oct 2010 21:53:20 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: u10g2000yqk.googlegroups.com; posting-host=88.84.91.37;
 posting-account=MJRf0QoAAAD4D6NLVoX5XW3Tna9p9iQ7
User-Agent: G2/1.0
X-HTTP-Via: 1.1 DAVINCI3
X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.2.10)
 Gecko/20100914 Firefox/3.6.10,gzip(gfe)
Xref: g2news2.google.com comp.lang.ada:15489
Date: 2010-10-13T14:53:14-07:00
List-Id: <comp.lang.ada>

> If you think you need to rely on this, it is extremely likely that there is
> something you don't understand.
>

I have a record with an array member constrained. I want to obtain an
unconstrained accesss, because I want to return it in a procedure. I
want to return an access, because returning an array implies a copy.
And I want the caller to get the bounds of the returned access at
runtime.

type buffer is array(Natural range<>) of Unsigned_8;
type buffer_access is access all buffer;

type t is record
   data: buffer(1..4);
end record;

a_t: t := .....;

abuf_access := a_t.data'Unrestricted_Access;

Note that this has two dependencies with GNAT:
 - Access to arrays use double pointers. So in the obtained access one
can obtain the bounds correctly, with abuf_access'First,
abuf_access'Last.

 - The attribute Unrestricted_Access.

I cannot understand why a procedure that expects an unconstrained
array can be passed a constrained one, and it is not possible to get
an access to an unconstrained array from a constrained one.