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From: stefan-lucks@see-the.signature
Subject: Re: and then... (a curiosity)
Date: Sun, 7 Sep 2008 18:45:54 +0200
Date: 2008-09-07T18:45:54+02:00	[thread overview]
Message-ID: <Pine.LNX.4.64.0809071836520.2848@medsec1.medien.uni-weimar.de> (raw)
In-Reply-To: <118b62boky4l7.4par5acnu8os$.dlg@40tude.net>

On Fri, 5 Sep 2008, Dmitry A. Kazakov wrote:

> On Fri, 05 Sep 2008 10:14:47 -0400, Robert A Duff wrote:
>  
> > Some more questions about 3.
> 
> (The proposal is, as I understood it, IMO workable, but it potentially has
> a heavy overhead and it does not solve the problem. It is not the
> mathematical interpretation of "and", and its semantics is not better than
> one of "and then". Further IMO the problem lies elsewhere. Nevertheless, I
> will take the liberty of explaining the semantics, and consequences)

Once again, I didn't actually *propose* anything. But you described some 
ideas I had very well, Dmitry, thank you. 

> No, all arguments are eagerly evaluated. It is simply so that exception
> becomes a legal value of "Universal_Boolean". The exception is raised when
> such value is converted to Boolean in the context where a Boolean is
> expected. Like in "if". But "and", "or", "xor", "not" operate on
> "Universal_Boolean".

I would consider both the option of introducing lazy evaluation (not as a 
special "compiler magic" thing only for "and", but in general), or 
extending the type Boolean, as described by you.

> (I hope Stefan will correct me if I misinterpreted his proposal)

No problem! You expressed one of the ideas I had in my mind better than I 
would have done it myself. But once again, I didn't make a proposal. I 
just shared some thoughts about the non-shortcut-and (and -or) in "if" 
expressions, which in my experience is a common error-pattern in Ada. 
(Other languages have more and worse traps than Ada, but nevertheless ...)



-- 
------ Stefan Lucks   --  Bauhaus-University Weimar  --   Germany  ------
               Stefan dot Lucks at uni minus weimar dot de
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------




  reply	other threads:[~2008-09-07 16:45 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
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 [this message]
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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