From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: [Not important] the “not null” notation in Ada 2005
Date: Sat, 26 Mar 2011 08:02:45 +0100
Date: 2011-03-26T08:02:44+01:00 [thread overview]
Message-ID: <mivzlnoflrrg$.q4l1m4pidzdt$.dlg@40tude.net> (raw)
In-Reply-To: op.vswop2cgule2fv@index.ici
On Fri, 25 Mar 2011 16:45:28 +0100, Yannick Duchêne (Hibou57) wrote:
> I remember some peoples says here, this is a pity to have “not null”
> annotations, while the case which should be clearly marked, is the one
> where a reference may be null. I'm OK with that principle. But concretely
> what would have been the notation ? “may be null” ? Two reserved words
> added for that ? A simple “null” would not have been really expressive
> (just a though I get right a few minutes ago).
No notation needed. Before Ada 2005 broke it, "access T" was not null, if
anonymous type is what you mean.
Named type is a different beast. When you declare a named access type "not
null" is a constraint. You cannot have a constrained subtype before the
type.
Yet another story is an access type, which does not have null as a value.
It is not much different from being constrained. Compare it with integer
types. When you declare:
type P is range 1..2;
You do not eliminate 0, as you might think. P has a "parent type," which
still has 0 (P'Base).
So which case you meant? (:-))
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
prev parent reply other threads:[~2011-03-26 7:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-25 15:45 [Not important] the “not null” notation in Ada 2005 Yannick Duchêne (Hibou57)
2011-03-25 15:51 ` Robert A Duff
2011-03-25 16:43 ` Yannick Duchêne (Hibou57)
2011-03-25 17:13 ` Robert A Duff
2011-03-25 17:29 ` Yannick Duchêne (Hibou57)
2011-03-26 7:02 ` Dmitry A. Kazakov [this message]
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