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: 103376,8a34575d5eb275cb
X-Google-Attributes: gid103376,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news1.google.com!postnews.google.com!v15g2000yqn.googlegroups.com!not-for-mail
From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Load an object from a file
Date: Fri, 3 Apr 2009 13:22:19 -0700 (PDT)
Organization: http://groups.google.com
Message-ID: 
 <dcb9272d-f2b7-409f-99ea-1e90f79c9c95@v15g2000yqn.googlegroups.com>
References: <49d5fa88$0$2862$ba620e4c@news.skynet.be>
 <443d72ca-5bbd-46a3-84c6-e8bd984e5b80@k41g2000yqh.googlegroups.com>
	<49d628f5$0$2865$ba620e4c@news.skynet.be>
 <49d6346e$0$32681$9b4e6d93@newsspool2.arcor-online.net>
	<f25c8e68-c3cc-434d-bbe7-d18cd6258add@q30g2000prq.googlegroups.com>
NNTP-Posting-Host: 94.108.129.105
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1238790139 31427 127.0.0.1 (3 Apr 2009 20:22:19
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Fri, 3 Apr 2009 20:22:19 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: v15g2000yqn.googlegroups.com; posting-host=94.108.129.105;
	posting-account=pcLQNgkAAAD9TrXkhkIgiY6-MDtJjIlC
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.7)
	Gecko/2009030810 Iceweasel/3.0.7 (Debian-3.0.7-1),gzip(gfe),gzip(gfe)
Xref: g2news1.google.com comp.lang.ada:4428
Date: 2009-04-03T13:22:19-07:00
List-Id: <comp.lang.ada>

Adam Beneschan wrote on comp.lang.ada:
> P.S. You may need to be a bit cautious if you define U2 as a modular
> type, as Ludovic suggested, and then use it as the base type of an
> unconstrained array. =A0If you define
>
> =A0 =A0 type Some_Array is array (u2 range <>) of u2;
>
> you might be tempted to write code like this:
>
> =A0 =A0 procedure Do_Some_Operation (Count : U2) is
> =A0 =A0 =A0 =A0Result : Some_Array (0 .. Count - 1);
> =A0 =A0 =A0 =A0...
>
> If you call Do_Some_Operation(0), Result is not going to be an empty
> array like you expect, but rather an array too large to fit in your
> computer, because 0-1 doesn't return a negative number for modular
> types but rather a very large positive number.

In the light of Adam's remark,

type u2 is mod 2 ** 16;

is the exact equivalent of Java's u2, but we now see that Java's u2
does _not_ represent the problem domain accurately; therefore defining
u2 in Ada as

type u2 is range 0 .. 2 ** 16 - 1;

does reflect the problem domain accurately (i.e. in the problem
domain, there is no wrap-around semantics) at the expense, perhaps, of
exposing bugs in the Java code :)

--
Ludovic Brenta.