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=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,a20ed8b5fc3cad81
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news2.google.com!postnews.google.com!b28g2000cwb.googlegroups.com!not-for-mail
From: "Adam Beneschan" <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Extended 'Succ attribute?
Date: 22 Nov 2006 18:04:37 -0800
Organization: http://groups.google.com
Message-ID: <1164247477.100738.32670@b28g2000cwb.googlegroups.com>
References: <1164243308.957573.223990@l39g2000cwd.googlegroups.com>
NNTP-Posting-Host: 66.126.103.122
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1164247482 15569 127.0.0.1 (23 Nov 2006 02:04:42
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Thu, 23 Nov 2006 02:04:42 +0000 (UTC)
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux x86_64; en-US;
 rv:1.7.12) Gecko/20050922 Fedora/1.7.12-1.3.1,gzip(gfe),gzip(gfe)
Complaints-To: groups-abuse@google.com
Injection-Info: b28g2000cwb.googlegroups.com; posting-host=66.126.103.122;
   posting-account=cw1zeQwAAABOY2vF_g6V_9cdsyY_wV9w
Xref: g2news2.google.com comp.lang.ada:7654
Date: 2006-11-22T18:04:37-08:00
List-Id: <comp.lang.ada>

J=E9r=E9mie Lumbroso wrote:
> Hello,
>
> I just started Ada and was wondering if there is a way to make the Succ
> attribute of discrete types behave in a cyclic manner (akin to the
> modular type):
>
>     type T_DAY is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
>
>     ...
>
>     day :=3D T_DAY'(Sun);
>     day :=3D T_DAY'Succ(day);  -- that this returns 'Mon' instead of
>                              -- a type constraint error
>
> I could of course define my own function to do this, but I wish to know
> if there is a way to get Ada to do it itself.

No.

The best you could do would be to declare a modular type, and then
declare Mon, Tue, etc. as constants of that type:

    type T_DAY is mod 7;
    Mon : constant T_DAY :=3D 0;
    Tue : constant T_DAY :=3D 1;
etc.

Then T_DAY'Succ(X) will wrap around.  But I don't see any advantage to
doing things this way.  I'd
just make it an enumeration literal and define your own Succ function.

                        -- Adam