From: Brian Drummond <brian_drummond@btconnect.com>
Subject: Re: and then... (a curiosity)
Date: Thu, 04 Sep 2008 23:09:02 +0100
Date: 2008-09-04T23:09:02+01:00 [thread overview]
Message-ID: <fsm0c41mv7ubhp3j6ervvurk1ns0btcmsl@4ax.com> (raw)
In-Reply-To: wcctzcxgr4w.fsf@shell01.TheWorld.com
On Wed, 03 Sep 2008 11:56:15 -0400, Robert A Duff
<bobduff@shell01.TheWorld.com> wrote:
>Brian Drummond <brian_drummond@btconnect.com> writes:
>> But it does illustrate that (I) "and then" (short circuit form, order
>> guaranteed) and (II) "and" (short circuit permitted, but not guaranteed,
>> order not guaranteed) are properly separate operations.
>>
>> For cases such as the logging example (semantics require both to be
>> evaluated) my personal choice would be to explicitly evaluate both, and
>> combine their evaluation results, as elsewhere in this thread.
>>
>> Is my understanding of Ada correct in expecting this is the only way to
>> guarantee evaluation of both? ( i.e. Ada handles "and" as (II) above)
>
>No. Ada guarantees that both arguments of "and" are evaluated.
>Of course if the compiler knows that evaluation has no effect, it
>doesn't need to generate any code -- that would be the case for
>"X > 0", for example.
In the process it must give up some opportunities for optimisation
(though I suspect, not as many as e.g. mandating the short-circuit form
in a particular order).
Note: I am not complaining that this is an unreasonable design decision.
- Brian
next prev parent reply other threads:[~2008-09-04 22:09 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-29 21:06 and then... (a curiosity) mockturtle
2008-08-29 21:47 ` Samuel Tardieu
2008-08-30 21:28 ` Maciej Sobczak
2008-08-31 8:28 ` Georg Bauhaus
2008-08-31 23:21 ` Ray Blaak
2008-09-01 8:05 ` Martin Krischik
2008-09-01 17:56 ` Ray Blaak
2008-09-02 6:53 ` Martin Krischik
2008-09-02 14:56 ` Adam Beneschan
2008-09-02 16:28 ` Ray Blaak
2008-09-02 16:26 ` Ray Blaak
2008-09-02 20:50 ` Robert A Duff
2008-09-03 12:35 ` Brian Drummond
2008-09-03 15:56 ` Robert A Duff
2008-09-04 22:09 ` Brian Drummond [this message]
2008-09-03 21:01 ` Vinzent Hoefler
2008-09-02 14:50 ` Adam Beneschan
2008-08-29 22:28 ` Adam Beneschan
2008-08-30 1:06 ` Jeffrey R. Carter
2008-08-30 11:21 ` Dmitry A. Kazakov
2008-08-30 15:35 ` Peter C. Chapin
2008-09-02 15:06 ` Adam Beneschan
2008-09-02 3:41 ` Steve
2008-09-02 7:48 ` stefan-lucks
2008-09-02 8:57 ` Martin Krischik
2008-09-02 10:50 ` stefan-lucks
2008-09-02 10:33 ` Ludovic Brenta
2008-09-02 13:32 ` stefan-lucks
2008-09-02 12:53 ` Ludovic Brenta
2008-09-02 17:32 ` Georg Bauhaus
2008-09-03 13:14 ` stefan-lucks
2008-09-03 12:44 ` Dmitry A. Kazakov
2008-09-02 13:39 ` stefan-lucks
2008-09-02 13:40 ` stefan-lucks
2008-09-02 16:48 ` Dmitry A. Kazakov
2008-09-02 17:00 ` Keith Thompson
2008-09-02 19:15 ` Simon Wright
2008-09-02 20:37 ` Robert A Duff
2008-09-02 20:58 ` Jeffrey R. Carter
2008-09-02 21:08 ` Robert A Duff
2008-09-03 12:24 ` Pascal Obry
2008-09-02 22:34 ` Santiago Urueña
2008-09-03 5:56 ` Robert A Duff
2008-09-03 6:55 ` Santiago Urueña
2008-09-03 14:14 ` Adam Beneschan
2008-09-03 0:11 ` Randy Brukardt
2008-09-02 17:20 ` Georg Bauhaus
2008-09-04 1:05 ` Stephen Leake
2008-09-04 6:45 ` stefan-lucks
2008-09-04 7:35 ` Dmitry A. Kazakov
2008-09-04 12:04 ` stefan-lucks
2008-09-04 13:00 ` Dmitry A. Kazakov
2008-09-04 19:05 ` stefan-lucks
2008-09-04 20:28 ` Dmitry A. Kazakov
2008-09-05 6:57 ` stefan-lucks
2008-09-05 6:34 ` Ray Blaak
2008-09-05 14:14 ` Robert A Duff
2008-09-05 15:04 ` Dmitry A. Kazakov
2008-09-07 16:45 ` stefan-lucks
2008-09-05 15:14 ` Hyman Rosen
2008-09-05 15:59 ` Adam Beneschan
2008-09-05 16:10 ` Hyman Rosen
2008-09-07 16:36 ` stefan-lucks
2008-09-07 16:08 ` Gautier
2008-09-04 7:39 ` Karel Th�nissen
2008-09-04 12:12 ` stefan-lucks
2008-09-04 15:13 ` Georg Bauhaus
2008-09-04 15:16 ` Karel Th�nissen
2008-09-04 15:42 ` Dmitry A. Kazakov
2008-09-04 19:27 ` stefan-lucks
2008-09-04 19:43 ` stefan-lucks
2008-09-04 19:40 ` Georg Bauhaus
2008-09-05 7:00 ` stefan-lucks
2008-09-05 6:35 ` Ray Blaak
2008-09-04 20:06 ` Karel Th�nissen
2008-09-05 7:44 ` stefan-lucks
2008-09-05 6:41 ` Vinzent Hoefler
2008-09-04 20:09 ` Karel Th�nissen
2008-09-05 7:25 ` stefan-lucks
2008-09-05 6:37 ` Ray Blaak
2008-09-05 8:20 ` stefan-lucks
2008-09-05 13:57 ` Robert A Duff
2008-09-04 16:33 ` Dmitry A. Kazakov
2008-09-04 19:31 ` stefan-lucks
2008-09-04 19:59 ` Karel Th�nissen
2008-09-05 7:27 ` stefan-lucks
2008-09-05 8:38 ` Ludovic Brenta
2008-09-04 20:17 ` Dmitry A. Kazakov
2008-09-05 13:26 ` Robert A Duff
2008-09-05 13:49 ` Robert A Duff
2008-09-03 1:24 ` Stephen Leake
2008-09-03 3:31 ` tmoran
2008-09-03 13:22 ` stefan-lucks
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