From: Georg Bauhaus <bauhaus.rm.tsoh@maps.futureapps.de>
Subject: Re: Self pointer in limited record
Date: Wed, 05 Sep 2007 23:38:34 +0200
Date: 2007-09-05T23:33:31+02:00 [thread overview]
Message-ID: <46df20aa$0$30370$9b4e6d93@newsspool4.arcor-online.net> (raw)
In-Reply-To: <z9bv2evgi034$.c5w7oonnbudf$.dlg@40tude.net>
Dmitry A. Kazakov wrote:
[snip all kinds of buzz words :-]
>>> The point was "to have one instance" and "to be a FSM" are unrelated.
>> There is a point of view from which the concept "to have one instance"
>> and "to be a FSM" are unrelated. When writing an Ada program, you may
>> have a point of view from which the concept "to have one instance" and
>> "to be a FSM" coincide on a suitable conceptual level. It is the level
>> on which an abstract state machine package is explained.
>
> Can I take a protected object or a task to implement either?
You can take a package and implement either.
> (I have no respect to singletons. They might have some sacral meaning for
> some OO proponents, but that was always beyond my understanding.)
They can avoid surprises and nasty issues because they enforce body
visibility of data objects. Example:
<start of declarative part>
package S is
type T is limited private;
procedure op(x: in out T);
private
type T is limited record
null;
end record;
end S;
package body S is separate;
-- ... a different programmer has a clever idea
-- ... and adds another ad hoc procedure for
-- ... debugging porposes
procedure bar(x: S.T) is
begin
raise Program_Error;
end bar;
use S;
item: T;
begin
bar(item);
end;
This is of course an artificial example. However, it serves to
demonstrate a few effects. Once the object type T is visible
outside the package (being declared in the public part of S), objects
can be declared outside of S. Adding a subprogram like Bar will in a
sense break grouping (where to look for bar which takes a T).
If the author of S had intended an upper bound on instances of T,
say one instance, then enforcing this limit will require more work.
These issues go away with a simple abstract state machine style package.
next prev parent reply other threads:[~2007-09-05 21:38 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-04 19:31 Self pointer in limited record Maciej Sobczak
2007-07-05 8:22 ` Dmitry A. Kazakov
2007-07-05 10:35 ` Maciej Sobczak
2007-07-05 11:01 ` Pascal Obry
2007-07-05 11:14 ` Georg Bauhaus
2007-07-05 12:36 ` Dmitry A. Kazakov
2007-08-31 16:47 ` amado.alves
2007-08-31 17:09 ` Pascal Obry
2007-08-31 17:37 ` Adam Beneschan
2007-08-31 18:26 ` Jeffrey R. Carter
2007-08-31 19:33 ` Dmitry A. Kazakov
2007-09-01 13:33 ` Georg Bauhaus
2007-09-01 13:46 ` Dmitry A. Kazakov
2007-09-01 14:15 ` Georg Bauhaus
2007-09-01 16:03 ` Dmitry A. Kazakov
2007-09-01 19:49 ` Georg Bauhaus
2007-09-01 20:09 ` Dmitry A. Kazakov
2007-09-02 21:37 ` Georg Bauhaus
[not found] ` <re7ei5lc7dzf$.11qtcnh35jmzg$.dlg@40tude.net>
2007-09-03 10:51 ` Georg Bauhaus
2007-09-03 14:17 ` Dmitry A. Kazakov
2007-09-03 15:55 ` Jean-Pierre Rosen
2007-09-03 19:17 ` Dmitry A. Kazakov
2007-09-03 19:32 ` Markus E L
2007-09-03 20:14 ` Georg Bauhaus
2007-09-04 8:24 ` Dmitry A. Kazakov
2007-09-04 9:36 ` Jean-Pierre Rosen
2007-09-04 10:14 ` Dmitry A. Kazakov
2007-09-05 10:49 ` Georg Bauhaus
2007-09-05 12:04 ` Dmitry A. Kazakov
2007-09-05 13:12 ` Jean-Pierre Rosen
2007-09-05 15:10 ` Dmitry A. Kazakov
2007-09-05 16:25 ` Jean-Pierre Rosen
2007-09-05 19:52 ` Dmitry A. Kazakov
2007-09-06 7:19 ` Jean-Pierre Rosen
2007-09-06 9:28 ` Dmitry A. Kazakov
2007-09-06 11:53 ` Jean-Pierre Rosen
2007-09-06 15:35 ` Dmitry A. Kazakov
2007-09-05 18:31 ` Georg Bauhaus
2007-09-05 19:52 ` Dmitry A. Kazakov
2007-09-05 21:38 ` Georg Bauhaus [this message]
2007-09-06 7:37 ` Dmitry A. Kazakov
2007-09-06 10:26 ` Georg Bauhaus
2007-09-06 12:25 ` Dmitry A. Kazakov
2007-09-08 1:27 ` Randy Brukardt
2007-09-06 9:14 ` Markus E L
2007-09-06 9:48 ` Dmitry A. Kazakov
2007-09-04 8:23 ` Jean-Pierre Rosen
2007-10-31 23:59 ` adaworks
2007-09-03 20:38 ` Georg Bauhaus
2007-09-04 8:24 ` Dmitry A. Kazakov
2007-09-03 7:54 ` Jean-Pierre Rosen
2007-09-01 15:33 ` Markus E L
2007-09-04 14:55 ` Adam Beneschan
2007-09-04 15:09 ` Jean-Pierre Rosen
2007-09-08 1:36 ` Randy Brukardt
2007-09-04 17:31 ` Georg Bauhaus
2007-09-08 1:16 ` Randy Brukardt
2007-09-10 16:27 ` amado.alves
2007-09-10 17:13 ` Adam Beneschan
2007-09-10 19:00 ` Dmitry A. Kazakov
2007-09-11 3:12 ` Randy Brukardt
2007-09-11 9:38 ` Dmitry A. Kazakov
2007-09-12 21:57 ` Randy Brukardt
2007-09-13 8:03 ` Dmitry A. Kazakov
2007-09-13 21:37 ` Randy Brukardt
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