From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
Subject: Re: about the new Ada 2012 pre/post conditions
Date: Wed, 27 Jun 2012 12:30:41 +0200
Date: 2012-06-27T12:30:41+02:00 [thread overview]
Message-ID: <4feae0d1$0$6568$9b4e6d93@newsspool3.arcor-online.net> (raw)
In-Reply-To: <1et105d0sks1i.pcgog9ym17ym.dlg@40tude.net>
On 27.06.12 10:52, Dmitry A. Kazakov wrote:
> On Wed, 27 Jun 2012 10:23:47 +0200, Georg Bauhaus wrote:
>
>> On 26.06.12 21:43, Dmitry A. Kazakov wrote:
>>
>>>> <body> is supposed to
>>>> implement something that essentially agrees with Pre/Post.
>>>
>>> Sure. Anything that follows "then" in any if-statement implements something
>>> in agreement with the condition tested by the statement. That is the nature
>>> of if-statements.
>>
>> That's not what agreement of<body> with Pre/Post should mean,
>
> If that is not, change the code. Bugs not to be tolerated.
What bug? I am defining what it means for a statement
to, in essential effects, agree with what an explicitly
stated Pre says, the latter being part of an ante factum
contract. Consider
A:
if Pre (...) then
A (X) := 1;
else
raise Assertion_Failure;
end if;
B:
A (X) := 1;
A and B can be shown to both be implementations of the behavior
that some contract stipulates.
Just like these implementations of a Procedure Add_2 (X : in out Integer)
can be essentially the same
X := X + 1; null;
X := X + 1; X := X + 2;
A compiler might produce code for these that, for example, is not efficient
enough. If there is no efficiency constraint stated as part of the contract,
the difference is unessential, and the two implementations are essentially
the same, judging by the contract.
> They evidently do not have same effect. Prove that they do!
A and B have *essentially* the same effect once the program
is correct. "Essential effects" is an important consideration
when designing a program. With or without DbC, one choice can be
just as good as another if they yield essentially the same
effect. Unessential things do not count here. The bug hunting
features of DbC do, as does the value it adds to documentation.
We would not be using compilers or high level languages at all
if there wasn't that notion of "essentially the same".
next prev parent reply other threads:[~2012-06-27 10:30 UTC|newest]
Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-20 13:39 about the new Ada 2012 pre/post conditions Nasser M. Abbasi
2012-06-20 14:02 ` Georg Bauhaus
2012-06-20 14:13 ` Dmitry A. Kazakov
2012-06-20 14:24 ` Nasser M. Abbasi
2012-06-20 14:37 ` Dmitry A. Kazakov
2012-06-20 17:02 ` Georg Bauhaus
2012-06-20 18:28 ` Dmitry A. Kazakov
2012-06-21 20:32 ` Randy Brukardt
2012-06-22 7:23 ` Dmitry A. Kazakov
2012-06-22 11:54 ` Georg Bauhaus
2012-06-22 12:39 ` Georg Bauhaus
2012-06-22 12:43 ` Dmitry A. Kazakov
2012-06-22 14:30 ` Georg Bauhaus
2012-06-22 14:36 ` Georg Bauhaus
2012-06-22 15:05 ` Dmitry A. Kazakov
2012-06-22 15:52 ` Georg Bauhaus
2012-06-22 16:35 ` Dmitry A. Kazakov
2012-06-22 16:53 ` Georg Bauhaus
2012-06-22 16:45 ` Georg Bauhaus
2012-06-22 17:24 ` Dmitry A. Kazakov
2012-06-22 19:41 ` Randy Brukardt
2012-06-22 23:08 ` Dmitry A. Kazakov
2012-06-23 10:46 ` Georg Bauhaus
2012-06-23 11:01 ` Dmitry A. Kazakov
2012-06-23 17:46 ` AdaMagica
2012-06-23 19:23 ` Dmitry A. Kazakov
2012-06-24 14:59 ` Georg Bauhaus
2012-06-24 16:06 ` Dmitry A. Kazakov
2012-06-24 19:51 ` Georg Bauhaus
2012-06-25 7:48 ` Dmitry A. Kazakov
2012-06-25 10:10 ` Georg Bauhaus
2012-06-25 8:08 ` Dmitry A. Kazakov
2012-06-25 10:17 ` Georg Bauhaus
2012-06-25 11:54 ` Dmitry A. Kazakov
2012-06-25 12:39 ` Georg Bauhaus
2012-06-25 12:51 ` Georg Bauhaus
2012-06-25 13:19 ` Dmitry A. Kazakov
2012-06-25 16:43 ` Georg Bauhaus
2012-06-25 14:08 ` stefan-lucks
2012-06-25 14:36 ` Dmitry A. Kazakov
2012-06-25 14:37 ` Dmitry A. Kazakov
2012-06-25 16:26 ` stefan-lucks
2012-06-25 19:42 ` Dmitry A. Kazakov
2012-06-26 11:50 ` stefan-lucks
2012-06-26 13:07 ` Dmitry A. Kazakov
2012-06-26 13:49 ` Georg Bauhaus
2012-06-26 14:45 ` Dmitry A. Kazakov
2012-06-26 16:48 ` Georg Bauhaus
2012-06-26 19:43 ` Dmitry A. Kazakov
2012-06-27 8:23 ` Georg Bauhaus
2012-06-27 8:52 ` Dmitry A. Kazakov
2012-06-27 10:30 ` Georg Bauhaus [this message]
2012-06-27 12:19 ` Dmitry A. Kazakov
2012-06-27 13:41 ` Nasser M. Abbasi
2012-06-28 7:00 ` Georg Bauhaus
2012-06-27 15:08 ` Georg Bauhaus
2012-06-29 21:03 ` Shark8
2012-06-30 8:26 ` Dmitry A. Kazakov
2012-06-30 12:54 ` Niklas Holsti
2012-07-05 2:58 ` Shark8
2012-07-05 7:24 ` Dmitry A. Kazakov
2012-07-06 6:23 ` Shark8
2012-07-06 7:57 ` Dmitry A. Kazakov
2012-07-07 1:09 ` Randy Brukardt
2012-07-07 8:44 ` Dmitry A. Kazakov
2012-06-26 14:54 ` stefan-lucks
2012-06-26 15:14 ` Dmitry A. Kazakov
2012-07-03 5:28 ` Randy Brukardt
2012-07-03 12:53 ` Dmitry A. Kazakov
2012-07-03 13:48 ` Georg Bauhaus
2012-07-03 14:06 ` Dmitry A. Kazakov
2012-07-03 16:12 ` Georg Bauhaus
2012-07-03 16:45 ` Georg Bauhaus
2012-07-05 1:45 ` Randy Brukardt
2012-07-05 7:48 ` Dmitry A. Kazakov
2012-07-05 19:11 ` Adam Beneschan
2012-07-05 19:55 ` Dmitry A. Kazakov
2012-07-06 7:41 ` Georg Bauhaus
2012-07-06 7:47 ` Georg Bauhaus
2012-07-06 8:05 ` Dmitry A. Kazakov
2012-07-06 8:30 ` Georg Bauhaus
2012-07-06 9:01 ` Dmitry A. Kazakov
2012-07-06 11:33 ` Simon Wright
2012-07-06 13:25 ` Dmitry A. Kazakov
2012-07-06 12:07 ` Georg Bauhaus
2012-07-06 13:37 ` Dmitry A. Kazakov
2012-07-06 16:17 ` Georg Bauhaus
2012-07-06 16:34 ` Georg Bauhaus
2012-07-06 19:18 ` Dmitry A. Kazakov
2012-07-07 1:24 ` Randy Brukardt
2012-07-07 9:09 ` Dmitry A. Kazakov
2012-07-07 1:18 ` Randy Brukardt
2012-07-07 9:14 ` Dmitry A. Kazakov
2012-07-07 12:06 ` Georg Bauhaus
2012-07-07 12:54 ` Dmitry A. Kazakov
2012-07-07 13:31 ` Georg Bauhaus
2012-07-03 5:10 ` Randy Brukardt
2012-07-03 4:51 ` Randy Brukardt
2012-07-03 12:46 ` Dmitry A. Kazakov
2012-07-05 2:18 ` Randy Brukardt
2012-07-05 8:48 ` Dmitry A. Kazakov
2012-07-05 12:07 ` Georg Bauhaus
2012-07-05 12:13 ` Georg Bauhaus
2012-07-05 12:31 ` Dmitry A. Kazakov
2012-07-05 18:16 ` Georg Bauhaus
2012-07-05 19:57 ` Dmitry A. Kazakov
2012-07-06 6:53 ` Georg Bauhaus
2012-07-07 0:43 ` Randy Brukardt
2012-07-07 8:06 ` Dmitry A. Kazakov
2012-07-07 11:17 ` Georg Bauhaus
2012-07-07 11:31 ` Dmitry A. Kazakov
2012-07-07 12:21 ` Georg Bauhaus
2012-07-07 13:03 ` Dmitry A. Kazakov
2012-06-20 19:18 ` Anh Vo
2012-06-20 20:16 ` Jeffrey R. Carter
2012-06-20 20:21 ` Jeffrey R. Carter
2012-06-20 20:51 ` Maciej Sobczak
2012-06-20 21:04 ` Dmitry A. Kazakov
2012-06-20 22:19 ` Robert A Duff
2012-06-21 6:32 ` Georg Bauhaus
2012-06-21 20:37 ` Randy Brukardt
2012-06-21 20:55 ` Jeffrey Carter
2012-06-22 19:15 ` Randy Brukardt
2012-06-21 20:23 ` Randy Brukardt
2012-06-22 7:34 ` Martin
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