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
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 border1.nntp.ams3.giganews.com!border2.nntp.ams3.giganews.com!border2.nntp.ams2.giganews.com!border4.nntp.ams.giganews.com!border2.nntp.ams.giganews.com!nntp.giganews.com!eternal-september.org!feeder.eternal-september.org!mx05.eternal-september.org!.POSTED!not-for-mail
From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Variant record limitation - what's a better solution?
Date: Wed, 03 Jul 2013 09:23:09 -0700
Organization: Also freenews.netfront.net; news.tornevall.net
Message-ID: <kr1ir1$asc$1@dont-email.me>
References: <0606a658-9816-4611-84dd-4f999bf6018e@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Wed, 3 Jul 2013 16:17:39 +0000 (UTC)
Injection-Info: mx05.eternal-september.org;
 posting-host="0ff79f536fa0097e04633d700dc31cb2";
 logging-data="11148"; mail-complaints-to="abuse@eternal-september.org";
 posting-account="U2FsdGVkX19cd7BMXxC9TVISWfHZgGqCT2eZSBO4FN4="
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:17.0) Gecko/17.0 Thunderbird/17.0
In-Reply-To: <0606a658-9816-4611-84dd-4f999bf6018e@googlegroups.com>
Cancel-Lock: sha1:PyZF00m7/MI5hYocKo2YSFHlsrA=
X-Original-Bytes: 2465
Date: 2013-07-03T09:23:09-07:00
List-Id: <comp.lang.ada>

On 07/03/2013 12:52 AM, Peter Brooks wrote:
>
> type
> my_object(X : size_type) is
>         record
>                name : string(1..80);
>                case X is
>                   when small => Y : small_type; -- line 20
>                   when medium => Y : medium_type; -- line 21
>                   when large => Y: large_type; -- line 22
>                end case;
>         end record;
>
> The errors are:
> line 21  'Y' conflicts with declaration at line 20
> line 22 'Y' conflicts with declaration at line 21
>
> I was hoping to have a different type depending on the case, but this doesn't seem allowed. What would achieve this?

The problem isn't the types but the component identifiers. Each component name 
must be unique, even across different variants. So you could do something like

type My_Object (Size : Size_ID) is record
    Name : String (1 .. 80);

    case Size is
    when Small =>
       Y_Small : Small_Value;
    when Medium =>
       Y_Medium : Medium_Value;
    when Large =>
       Y_Large : Large_Value;
    end case;
end record;

-- 
Jeff Carter
"My brain hurts!"
Monty Python's Flying Circus
21