From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: Half Constrained Array Types and Slices
Date: 10 Mar 2006 12:38:58 -0500
Date: 2006-03-10T12:38:58-05:00 [thread overview]
Message-ID: <wccmzfyurm5.fsf@shell01.TheWorld.com> (raw)
In-Reply-To: fg7Qf.2239$x94.1238@newsread1.news.pas.earthlink.net
"Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> writes:
> I think the index type should be discrete. But surely it doesn't need to
> be an integer:
>
> with Ada.Text_IO;
> procedure Null_Range is
> type A is (B, C);
>
> type D is array (A range <>) of Integer;
>
> E : D (C .. B);
> begin -- Null_Range
> Ada.Text_IO.Put_Line (Item => A'Image (E'Last) );
> end Null_Range;
>
> This is valid Ada.
Indeed it is. I don't think it's very useful, however.
My claim is that if you want empty arrays, you almost
certainly want to index them by (non-modular) integers.
Which is why I'm happy with the restriction in the Containers
library that Vector indices must be signed integers.
>... With GNAT, it outputs B. However, if D were a string
> type, "" would not be valid for it.
>
> > The idea that 'Range is equivalent to 'First..'Last seems reasonable to
> > me...
>
> I'm not saying it's a good idea. I'm just wondering what the
> consequences of it are.
I suppose the consequence is bugs -- rare cases where 'First and/or
'Last surprisingly raise Constraint_Error.
- Bob
next prev parent reply other threads:[~2006-03-10 17:38 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-02 5:00 Half Constrained Array Types and Slices Jeffrey R. Carter
2006-03-02 8:34 ` Dmitry A. Kazakov
2006-03-02 15:34 ` Georg Bauhaus
2006-03-02 19:37 ` Dmitry A. Kazakov
2006-03-02 20:06 ` Jeffrey R. Carter
2006-03-02 20:37 ` Dmitry A. Kazakov
2006-03-02 21:01 ` Robert A Duff
2006-03-02 20:40 ` Robert A Duff
2006-03-02 14:32 ` Larry Kilgallen
2006-03-02 20:08 ` Jeffrey R. Carter
2006-03-02 20:48 ` Robert A Duff
2006-03-06 2:16 ` Larry Kilgallen
2006-03-06 18:50 ` Martin Krischik
2006-03-02 20:38 ` Robert A Duff
2006-03-03 5:15 ` Jeffrey R. Carter
2006-03-03 8:57 ` Dmitry A. Kazakov
2006-03-03 23:41 ` Robert A Duff
2006-03-06 17:50 ` Jeff Carter
2006-03-06 18:31 ` Dmitry A. Kazakov
2006-03-07 19:02 ` Jeff Carter
2006-03-08 14:29 ` Dmitry A. Kazakov
2006-03-09 22:44 ` Robert A Duff
2006-03-10 8:46 ` Dmitry A. Kazakov
2006-03-06 19:49 ` Stefan Lucks
2006-03-08 17:36 ` brian.b.mcguinness
2006-03-08 17:56 ` Jeff Carter
2006-03-09 22:36 ` Robert A Duff
2006-03-10 4:28 ` Jeffrey R. Carter
2006-03-10 8:46 ` Dmitry A. Kazakov
2006-03-10 17:33 ` Robert A Duff
2006-03-10 21:24 ` Dmitry A. Kazakov
2006-03-10 17:38 ` Robert A Duff [this message]
2006-03-11 0:19 ` Randy Brukardt
2006-03-11 1:43 ` Jeffrey R. Carter
2006-03-11 8:38 ` Niklas Holsti
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