From: Maciej Sobczak <see.my.homepage@gmail.com>
Subject: Re: Discriminants of tagged types
Date: Wed, 27 Oct 2010 14:13:41 -0700 (PDT)
Date: 2010-10-27T14:13:41-07:00 [thread overview]
Message-ID: <3243de1d-c6b4-4845-ab5f-28ea4e9f5738@c20g2000yqj.googlegroups.com> (raw)
In-Reply-To: op.vk8r56y7ule2fv@garhos
On 27 Paź, 18:02, Yannick Duchêne (Hibou57) <yannick_duch...@yahoo.fr>
wrote:
> > as non-limited tagged types are nonsense anyway.
>
> Why ?
Because tagged types usually represent entities that are bound to some
resources and copying them is somewhere between cumbersome and
impossible. Communication channels, database connections, etc.
In Ada the only types I'm aware of which are tagged and which have
justifiable copy semantics are containers - but you might as well
argue that there is no reason whatsoever for them to be tagged, which
only proves my point.
In C++ (which I'm more familiar with) there is a rule of thumb saying
that polymorphic types (anything with a virtual function inside)
should have disallowed copy operations. As a rule of thumb it works
very well and I've yet to see a justifiable counter-example. The same
rule of thumb translated to Ada says: tagged types shall be limited.
--
Maciej Sobczak * http://www.inspirel.com
next prev parent reply other threads:[~2010-10-27 21:13 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-27 12:16 Discriminants of tagged types Maciej Sobczak
2010-10-27 12:34 ` Ludovic Brenta
2010-10-27 13:19 ` Dmitry A. Kazakov
2010-10-27 13:52 ` Robert A Duff
2010-10-27 14:12 ` Dmitry A. Kazakov
2010-10-27 13:44 ` Robert A Duff
2010-10-27 15:06 ` Adam Beneschan
2010-10-27 15:58 ` Yannick Duchêne (Hibou57)
2010-10-27 16:35 ` Vinzent Hoefler
2010-10-27 17:58 ` J-P. Rosen
2010-10-27 20:18 ` Yannick Duchêne (Hibou57)
2010-10-27 20:26 ` Adam Beneschan
2010-10-27 22:07 ` Yannick Duchêne (Hibou57)
2010-10-27 22:42 ` Adam Beneschan
2010-10-27 15:13 ` Maciej Sobczak
2010-10-27 16:02 ` Yannick Duchêne (Hibou57)
2010-10-27 21:13 ` Maciej Sobczak [this message]
2010-10-27 21:23 ` Ludovic Brenta
2010-10-28 8:38 ` Maciej Sobczak
2010-10-27 21:25 ` Vinzent Hoefler
2010-10-28 7:53 ` Dmitry A. Kazakov
2010-10-28 8:50 ` Maciej Sobczak
2010-10-28 10:28 ` Dmitry A. Kazakov
2010-10-28 17:48 ` Yannick Duchêne (Hibou57)
2010-10-29 18:59 ` Vinzent Hoefler
2010-10-30 21:05 ` Maciej Sobczak
2010-10-30 21:21 ` Vinzent Hoefler
2010-10-30 22:01 ` Yannick Duchêne (Hibou57)
2010-10-31 16:20 ` Maciej Sobczak
2010-10-31 17:04 ` Yannick Duchêne (Hibou57)
2010-10-31 18:36 ` Shark8
2010-10-31 21:06 ` Maciej Sobczak
2010-11-01 0:44 ` Shark8
2010-11-01 9:41 ` Maciej Sobczak
2010-10-27 16:06 ` Robert A Duff
2010-10-27 16:34 ` Yannick Duchêne (Hibou57)
2010-10-27 21:05 ` Maciej Sobczak
2010-10-28 0:35 ` Robert A Duff
2010-10-28 8:55 ` Maciej Sobczak
2010-10-27 21:28 ` Simon Wright
2010-10-27 13:54 ` J-P. Rosen
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