From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: Ada vs Eiffel - Ada programmer approach
Date: Mon, 8 Jun 2009 17:52:27 -0500
Date: 2009-06-08T17:52:27-05:00 [thread overview]
Message-ID: <h0k4o9$e37$1@munin.nbi.dk> (raw)
In-Reply-To: wccvdn6a55g.fsf@shell01.TheWorld.com
"Robert A Duff" writes:
...
> An invariant (whether it be a pragma, or some special syntax) would be
> attached to a type, and would mean "all objects of this type have
> this property, always" (except that maybe objects can temporarily
> violate their invariant, so long as the code puts it back).
>
> A related concept that has been discussed is "user-defined constraints".
> I'm not sure what the difference is, exactly -- I think with user-defined
> constraints, you can't "temporarily violate".
A user-defined constraint applies to a view (usually via a subtype), while
an invariant applies to a type (always). For instance, a user-defined
constraint can apply to a formal parameter but not to the actual parameter
object (just as any other constraint). Calling such a thing an "invariant"
would be completely wrong, because it's not invariant at all - the values
are only checked against the constraints at the points where Ada does
subtype conversions (and possibly a few others - this is TBD and hopefully
will be discussed at this week's ARG meeting).
Tucker explains the distinction somewhat in his new draft of AI-146 (to be
posted tonight, along with the ARG meeting agenda). There also is a partial
user-defined constraint AI (AI-153), but I got stuck over how invariant we
want these to be. Check them both out tomorrow.
Randy.
next prev parent reply other threads:[~2009-06-08 22:52 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-24 8:39 Ada vs Eiffel - Ada programmer approach Tomek Walkuski
2009-05-24 11:49 ` anon
2009-05-24 12:26 ` Georg Bauhaus
2009-05-24 12:17 ` Georg Bauhaus
2009-05-24 16:31 ` Pascal Obry
2009-05-25 16:32 ` Rugxulo
2009-05-26 13:37 ` Ludovic Brenta
2009-05-26 14:51 ` Dmitry A. Kazakov
2009-05-26 17:26 ` Georg Bauhaus
2009-05-26 17:39 ` Dmitry A. Kazakov
2009-05-26 17:59 ` Georg Bauhaus
2009-05-26 19:52 ` Dmitry A. Kazakov
2009-05-26 20:14 ` Pascal Obry
2009-05-26 20:25 ` Pascal Obry
2009-05-26 21:28 ` Dmitry A. Kazakov
2009-05-26 18:23 ` Jeffrey R. Carter
2009-05-26 15:07 ` Tim Rowe
2009-05-26 16:37 ` Georg Bauhaus
2009-05-28 8:37 ` Nicholas Paul Collin Gloucester
2009-06-01 16:22 ` Tim Rowe
2009-06-04 7:35 ` Hibou57 (Yannick Duchêne)
2009-06-04 9:46 ` Martin
2009-06-04 12:16 ` Hibou57 (Yannick Duchêne)
2009-06-04 9:56 ` Jean-Pierre Rosen
2009-06-16 6:58 ` ardjussi
2009-06-16 17:22 ` Jeffrey R. Carter
2009-05-26 18:21 ` Jeffrey R. Carter
2009-05-26 18:35 ` Dmitry A. Kazakov
2009-06-04 7:39 ` Hibou57 (Yannick Duchêne)
2009-06-04 9:02 ` Ludovic Brenta
2009-06-04 9:19 ` Dmitry A. Kazakov
2009-06-04 12:14 ` Hibou57 (Yannick Duchêne)
2009-06-04 14:14 ` Dmitry A. Kazakov
2009-06-04 16:45 ` Jeffrey R. Carter
2009-06-04 7:30 ` Hibou57 (Yannick Duchêne)
2009-06-04 7:55 ` Ludovic Brenta
2009-06-04 8:45 ` Georg Bauhaus
2009-06-04 9:03 ` Ludovic Brenta
2009-06-04 13:25 ` Robert A Duff
2009-06-04 13:39 ` Martin
2009-06-04 13:08 ` stefan-lucks
2009-06-08 12:41 ` Samuel Tardieu
2009-06-08 19:37 ` Robert A Duff
2009-06-08 22:52 ` Randy Brukardt [this message]
2009-06-09 7:39 ` Dmitry A. Kazakov
2009-06-10 6:55 ` Hibou57 (Yannick Duchêne)
2009-06-10 6:58 ` Hibou57 (Yannick Duchêne)
2009-06-10 11:10 ` Georg Bauhaus
2009-06-04 7:04 ` Hibou57 (Yannick Duchêne)
2009-06-04 6:04 ` Hibou57 (Yannick Duchêne)
2009-06-06 14:27 ` Marco
2009-06-06 15:37 ` Tomek Wałkuski
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