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: 103376,16dbd7ecc6a3d50c
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news3.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.de!t-online.de!news.tele.dk!feed118.news.tele.dk!news.tele.dk!small.news.tele.dk!skynet.be!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada decimal types
Date: Sat, 06 May 2006 16:48:06 +0100
Organization: Pushface
Message-ID: <m2k68zm9xl.fsf@grendel.local>
References: <sKG6g.6427$TT.4592@twister.nyroc.rr.com>
 <ZcKdnZAJrtSdH8bZRVn-jQ@comcast.com> <UwM6g.5985$Gg.392@twister.nyroc.rr.com>
 <lnmzdvttoc.fsf@nuthaus.mib.org> <C_17g.6056$Gg.2050@twister.nyroc.rr.com>
NNTP-Posting-Host: pogner.demon.co.uk
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Trace: news.demon.co.uk 1146930485 13195 62.49.19.209 (6 May 2006 15:48:05
 GMT)
X-Complaints-To: abuse@demon.net
NNTP-Posting-Date: Sat, 6 May 2006 15:48:05 +0000 (UTC)
Cancel-Lock: sha1:FdG76VRtNkS8ph6SCoM8IaJsBVg=
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (darwin)
Xref: g2news2.google.com comp.lang.ada:4116
Date: 2006-05-06T16:48:06+01:00
List-Id: <comp.lang.ada>

"REH" <me@you.com> writes:

> "Keith Thompson" <kst-u@mib.org> wrote in message 
> news:lnmzdvttoc.fsf@nuthaus.mib.org...

>> And it's the small, not the delta, that needs to be 1.0e-6.  If you
>> specify a delta of 1.0e-6 for an ordinary fixed-point type without
>> specifying the small, you'll (probabaly) get a small of 2.0**-20.
>> (As you probably know.)
>
> It's not an binary fixed point, but a decimal fixed point.  I believe the 
> small has to be a power of ten, not two.  Anyways, that is a good point. 
> For a decimal type, do I need to specify the small?

On GNAT, Duration (which is a plain fixed-point type) is effectively
implemented as

   type Duration is delta 1.0e-9;
   for Duration'Small use 1.0e-9;
   for Duration'Size use 64;

which means that the lsb is 1 nanosecond. I'm pretty sure that a
compiler has to do what you tell it here (or reject the unit).

It may well be that a decimal fixed point type would have exactly the
same effect but I have never used one.

type My_Duration is digits 9 delta 1.0e-9;
for My_Duration'Size use 64;

One point we came unstuck over: depending on your machine, the
alignment of a 64-bit value may end up as 8 bytes, whereas the
alignment of your POSIX-like representation would be 4 bytes.

Had you considered just using Duration?