From: Jeffrey Carter <spam@spam.com>
Subject: Re: type and subtype
Date: Mon, 25 Jul 2005 08:41:48 -0700
Date: 2005-07-25T08:41:48-07:00 [thread overview]
Message-ID: <0L7Fe.3$Jf6.1@dfw-service2.ext.ray.com> (raw)
In-Reply-To: <b4k0ygaqf0u4$.102vj4zdpubdy.dlg@40tude.net>
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Dmitry A. Kazakov wrote:
>
> I think that Ludovic's view is more consistent: checks are just a part of
> the conversion which otherwise is an identity function, because *presently*
> the representation is required to be same. But representation is an
> implementation detail and thus cannot count. Moreover it is very desirable
> to allow subtypes having different representations.
Try this with your favorite compiler:
Ada.Text_IO.Put_Line
(Item => "Integer'Size =" & Integer'Image (Integer'Size) ):
Ada.Text_IO.Put_Line
(Item => "Natural'Size =" & Integer'Image (Natural'Size) ):
You're likely to get something like
Integer'Size = 32
Natural'Size = 31
because representations of subtypes are not required to be the same.
We can also consider
type Rec (Length : Positive) is record
V : String (1 .. Length);
end record;
subtype Small is Rec (Length => 1);
subtype Big is Rec (length => 1_000);
where Small and Big have significantly different representations. Then
there are subtypes of variant record types with discriminants that
select different variants.
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next prev parent reply other threads:[~2005-07-25 15:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-24 14:24 type and subtype Douglas Chong
2005-07-24 14:39 ` Dmitry A. Kazakov
2005-07-25 17:07 ` Martin Krischik
2005-07-24 16:20 ` Ludovic Brenta
2005-07-24 16:40 ` Jeffrey Carter
2005-07-25 8:23 ` Dmitry A. Kazakov
2005-07-25 15:41 ` Jeffrey Carter [this message]
2005-07-25 21:59 ` Ludovic Brenta
2005-07-26 8:21 ` Dmitry A. Kazakov
2005-07-25 17:02 ` Martin Krischik
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