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
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!news.glorb.com!peer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!post01.iad.highwinds-media.com!fx05.iad.POSTED!not-for-mail
From: Shark8 <OneWingedShark@gmail.com>
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64;
 rv:30.0) Gecko/20100101 Thunderbird/30.0a1
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Subject: Re: "NULL" returned by a function
References: <ls3ec1$v3q$1@speranza.aioe.org>
In-Reply-To: <ls3ec1$v3q$1@speranza.aioe.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Message-ID: <gfbFv.200574$DV4.141453@fx05.iad>
X-Complaints-To: abuse@teranews.com
NNTP-Posting-Date: Fri, 08 Aug 2014 21:25:32 UTC
Organization: TeraNews.com
Date: Fri, 08 Aug 2014 15:25:30 -0600
X-Received-Bytes: 1318
X-Received-Body-CRC: 2407547508
Xref: news.eternal-september.org comp.lang.ada:21587
Date: 2014-08-08T15:25:30-06:00
List-Id: <comp.lang.ada>

On 08-Aug-14 15:10, Victor Porton wrote:
> What if I want to make a function which returns either a value of type T or
> a value signifying "nothing" (like null pointer)?

What's wrong with discriminated records?

Type Some_Container( Empty : Boolean ) is
   case Empty is
    When True  => Null;
    When False => Item : T;
   end case;
end record;

> To make things worse, T is a controlled type, so if we return just "access
> T" the finalization of the object of type T may be easily overlooked.

It seems that you're trying to program C/C++ in Ada, don't, that way 
lies only pain.