From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Array slices and types
Date: Thu, 21 Aug 2008 17:46:08 +0200
Date: 2008-08-21T17:46:11+02:00 [thread overview]
Message-ID: <7oae0iwhszmm.cazomantciz3.dlg@40tude.net> (raw)
In-Reply-To: fc112b42-285c-4ed5-ae78-34be4e60f6df@i20g2000prf.googlegroups.com
On Thu, 21 Aug 2008 07:44:29 -0700 (PDT), Adam Beneschan wrote:
> Sorry, Dmitry, but if you'll pardon the expression, you're a little
> off-base here. S'Base and S are subtypes of the same *type*.
No need to excuse, you are right, I don't see any semantic difference
between subtypes of "same" type and derived tagged types. Consequently, I
don't think it is worth to further maintain such difference in the
language.
> They
> may be different subtypes (have different constraints), but they're
> the same type. You're asking for an attribute that would give you a
> different type.
Yep, for that matter, tag is merely a constraint put on T'Class. Ada 83
model is capable to incorporate OO! We always knew that! (:-))
> There may be merit in having such an attribute (I
> haven't looked into it closely), but calling it 'Base would be a bad
> idea. S'Parent might be better.
Integer'Parent were Universal_Integer, I guess (:-))
> Niklas is asking for S'Base to be the unconstrained array subtype of
> the (possibly constrained) array subtype S. It would still fit into
> the definition of 'Base (3.5(15)). I'm not sure why this wasn't
> defined for array subtypes, or for any other type that could have
> discriminants; offhand I don't see how this would cause any problems.
I think that the reason was that S'Base was thought as a very low-level
thing, something like the least constrained type of the *same* internal
representation. For unconstrained arrays the representation is likely not
the same, they might have a dope. For other types nobody seemingly cared.
(:-))
IMO, if S'Base need to be extended, then that would require a bit firmer
foundation than the above.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2008-08-21 15:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-20 14:51 Array slices and types Maciej Sobczak
2008-08-20 15:26 ` Niklas Holsti
2008-08-20 15:46 ` Dmitry A. Kazakov
2008-08-20 18:52 ` Niklas Holsti
2008-08-20 20:01 ` Simon Wright
2008-08-21 5:26 ` Niklas Holsti
2008-08-21 8:53 ` Dmitry A. Kazakov
2008-08-21 14:44 ` Adam Beneschan
2008-08-21 15:46 ` Dmitry A. Kazakov [this message]
2008-08-22 4:30 ` Randy Brukardt
2008-08-20 17:47 ` stefan-lucks
2008-08-20 17:51 ` stefan-lucks
2008-08-20 20:45 ` Adam Beneschan
2008-08-21 21:16 ` Maciej Sobczak
2008-08-23 2:50 ` Steve
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