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=-1.1 required=5.0 tests=BAYES_00,
	PP_MIME_FAKE_ASCII_TEXT 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!feeder.eternal-september.org!nntp-feed.chiark.greenend.org.uk!ewrotcd!reality.xs3.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ok to assume type Duration is for more than one day?
Date: Mon, 23 Jan 2017 14:47:09 -0600
Organization: JSA Research & Innovation
Message-ID: <o65q4d$7g6$1@franka.jacob-sparre.dk>
References: <52d00223-69b9-4a5c-a2e0-aaa906d9b200@googlegroups.com>
 <o628eh$2vi$1@dont-email.me>
NNTP-Posting-Host: rrsoftware.com
X-Trace: franka.jacob-sparre.dk 1485204429 7686 24.196.82.226 (23 Jan 2017
 20:47:09 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Mon, 23 Jan 2017 20:47:09 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Response
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
Xref: news.eternal-september.org comp.lang.ada:33137
Date: 2017-01-23T14:47:09-06:00
List-Id: <comp.lang.ada>

Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org> wrote in message 
news:o628eh$2vi$1@dont-email.me...
> On 01/22/2017 12:37 PM, reinkor wrote:
>> As I understand from my textbook, type Duration is guaranteed to cover 
>> the range -86_400 .. 86_400 (number of seconds for one day). Does this 
>> mean that I take a considerable risk if I assume "Duration" can represent 
>> more than one day?
>
> Representing that range with an accuracy of 20 ms takes about 22 bits, so 
> most implementations will use at least 32 bits. The additional bits can be 
> used for a greater range, a smaller accuracy, or both. ±86,400 with an 
> accuracy of 20 µs takes about 32 bits, so a range of ±86,400 seems likely 
> for some 32-bit compilers.

I believe that in Janus/Ada, we allowed +/- 2 days to make math a bit 
easier, but the limit is not wildly different than the textbook version. (I 
think we ignored the recommendation for 20 µs). It would be odd for a 
non-64-bit compiler to use a 64-bit Duration, as 64-bit operations are 
relatively expensive on smaller machines.

                                 Randy.