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: 103376,8d7393f07c06c5e9
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,UTF8
Path: 
 g2news1.google.com!news1.google.com!npeer02.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!nx02.iad01.newshosting.com!newshosting.com!novia!transit4.readnews.com!news-out.readnews.com!postnews3.readnews.com!not-for-mail
Date: Sun, 29 Aug 2010 07:23:56 -0400
From: "Peter C. Chapin" <chapinp@acm.org>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US;
 rv:1.9.2.8) Gecko/20100802 Lightning/1.0b2 Thunderbird/3.1.2
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Subject: Re: Another question about fixed point types.
References: <4c7991c8$0$2375$4d3efbfe@news.sover.net>
 <op.vh6sgwjeule2fv@garhos>
In-Reply-To: <op.vh6sgwjeule2fv@garhos>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Message-ID: <4c7a4390$0$2390$4d3efbfe@news.sover.net>
Organization: SoVerNet (sover.net)
NNTP-Posting-Host: 5bc58871.news.sover.net
X-Trace: 
 DXC=8_m5W4g537DjcS8e6Z385KK6_LM2JZB_ClXHJXGi>>6I:WUUlR<856OgJk=U_]>;bHXk_dgNnbB]@
X-Complaints-To: abuse@sover.net
Xref: g2news1.google.com comp.lang.ada:13799
Date: 2010-08-29T07:23:56-04:00
List-Id: <comp.lang.ada>

On 2010-08-29 02:32, Yannick Duchêne (Hibou57) wrote:

> If it is symmetric around zero, that should explain your observations,
> as I would be very surprised if there would be provision for a hole
> somewhere. If it is symmetric around zero, and there is no two disjoint
> range, then this is include zero.
> 
> A tiny test program which would write first and last of the base type
> may tell more.

You're right. Thanks for pointing that out. Here is the range of
Julian_Day'Base that I obtained using a test program:

-9007199254740992.000 .. 9007199254740991.999

So my understanding was that for integral types the compiler is allowed
to allocate only the number of bits necessary to hold the range. For
example:

type Example_Type is range 1000 .. 1001;

The compiler is permitted (not required) to represent objects of type
Example_Type using only a single bit. But I guess this is a separate
issue. The base type, in which computations are done, might be wide even
if the compiler chooses to store the objects in a much small space.

So in my case as Phil explained computations on Julian Day are being
done, most likely, with a 64 bit type. Yet despite that, storage could
(perhaps) be using a smaller space since 64 bits is not needed to
represent the full range of Julian_Day at my specified resolution.

I understand that these details are compiler specific. However, it does
seem like my code, at least, should be portable in its effect.

Peter