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=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC 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!mx02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: function Is_Open (File : File_Type) return Boolean; :Text_io
Date: Wed, 28 Oct 2015 22:02:13 +0100
Organization: cbb software GmbH
Message-ID: <ki9oomfymbau.ckpvghtqa42n.dlg@40tude.net>
References: <f30bbb5d-ebfd-427b-8c16-88aeb8a61318@googlegroups.com>
 <87twpd2qlo.fsf@theworld.com> <1pj15r7pul7f1.15qgdyrc8k133$.dlg@40tude.net>
 <87pp0030c1.fsf@theworld.com> <135hiczk56x02.1xixcme8btbl4.dlg@40tude.net>
 <n0o9fb$3pq$2@dont-email.me> <1dzlgoh4u2j7t$.1un3dfy0oeigd$.dlg@40tude.net>
 <n0qa3q$th8$1@dont-email.me> <190shqocxd87d$.1d68ghgqgbvfs$.dlg@40tude.net>
 <87d1vy3f46.fsf@theworld.com>
Reply-To: mailbox@dmitry-kazakov.de
NNTP-Posting-Host: j6IQVb9uobzjXrpQLDU2rQ.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: 40tude_Dialog/2.0.15.1
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:28101
Date: 2015-10-28T22:02:13+01:00
List-Id: <comp.lang.ada>

On Wed, 28 Oct 2015 16:36:09 -0400, Bob Duff wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> On Wed, 28 Oct 2015 12:06:33 +0100, Georg Bauhaus wrote:
>>> However, another use of predicates is to document assumptions.
>>
>> Documenting *shall* have *no* run-time effects.
> 
> Really?!
> 
> In C, we can write:
> 
>     int num_gizmos = 0; // num_gizmos is always between 0 and 1024.
> 
> In Ada, we can write:
> 
>     type Gizmo_Count is range 0 .. 2**10;
>     Num_Gizmos: Gizmo_Count := 0;
> 
> IMHO, documenting the 0..1024 requirement in executable code is much
> better than using a comment:

How is that documenting? It is a direct instruction to the compiler.
Documentation is addressed to the human reader.

The advantage of Ada over C is that where in Ada you can instruct, in C the
only way is to document.

> By the way, what exactly do you mean by "shall"?  A native speaker of
> English doesn't usually use that word, except in legal documents and the
> like.  You seem to use the word "shall" to express opinions about the
> way things ought to be, which seems like an odd usage to me.

OK

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de