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: 103376,2a34b7ad6c6a0774
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news1.google.com!news1.google.com!news.glorb.com!news2.glorb.com!news.mv.net!nntp.TheWorld.com!not-for-mail
From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Efficiency of code generated by Ada compilers
Date: Mon, 09 Aug 2010 09:28:02 -0400
Organization: The World Public Access UNIX, Brookline, MA
Message-ID: <wccbp9bzzj1.fsf@shell01.TheWorld.com>
References: <f3c0cf89-6993-4b83-b4fe-8a920ce23a14@f6g2000yqa.googlegroups.com>
 <f208e17c-0511-4397-a13a-39a3da6eef5e@q22g2000yqm.googlegroups.com>
 <wccr5i985py.fsf@shell01.TheWorld.com>
 <1jmwhfp.roo31ybayx2bN%csampson@inetworld.net>
 <wcchbj4j09y.fsf@shell01.TheWorld.com>
 <i3o52d$p0i$1@news.eternal-september.org>
NNTP-Posting-Host: shell01.theworld.com
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
X-Trace: pcls6.std.com 1281360466 31955 192.74.137.71 (9 Aug 2010 13:27:46
 GMT)
X-Complaints-To: abuse@TheWorld.com
NNTP-Posting-Date: Mon, 9 Aug 2010 13:27:46 +0000 (UTC)
User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (irix)
Cancel-Lock: sha1:+SkxCkfrSJpcdhaPUcFh8hAlZVA=
Xref: g2news1.google.com comp.lang.ada:12979
Date: 2010-08-09T09:28:02-04:00
List-Id: <comp.lang.ada>

"J-P. Rosen" <rosen@adalog.fr> writes:

> Robert A Duff a �crit :
>> P.S. Can anybody recall the definition of "not" on modular
>> types, when the modulus is not a power of 2, without
>> looking it up? 
> Sure. Like any other operation. First you do the operation in the
> mathematical sense, then you take the mathematical result mod T'Modulus.

"and", "or", and "xor" are defined that way (bit-wise logical operation,
followed by "mod").  "not" is NOT defined as bit-wise "not" followed
by "mod".

    type T is mod 3;
    X : T := 2;
    ...
    X := not X;

Now X = 0.  2 = 2#10#.  Bit-wise "not" of that is 2#01#.
"mod" that by 3, and you get 2#1#.

>> Hint: It makes no sense.
> It makes sense because it is consistent with all other operations on
> modular types. Whether it is usefule is another story ;-)

It is neither consistent nor useful.  I'll stick with
"makes no sense".

>> The only feature
>> that's worse than "modular types" is "modular types with a
>> non-power-of-2 modulus".  ;-)
> Hmmm... Hash coded tables?

Signed integers work fine for that.  Except when you need
that one extra bit -- that's the problem.

- Bob