From: Marius Amado Alves <amado.alves@netcabo.pt>
To: comp.lang.ada@ada-france.org
Subject: Re: Why can't you create a out of order subtype?
Date: Wed, 2 Feb 2005 17:55:50 +0000
Date: 2005-02-02T17:55:50+00:00 [thread overview]
Message-ID: <mailman.114.1107367326.527.comp.lang.ada@ada-france.org> (raw)
In-Reply-To: <h5VLd.4199$cl1.3735@newsread3.news.pas.earthlink.net>
> ...
>> Another option that I think is much, much worse then the boolean array
>> would be create an overloaded type...
>> type msg is ( msg_a, msg_b, msg_c, msg_d, msg_e);
>> type vowelmsg ( msg_a, msg_e);
>> But as you know, msg.msg_e = 4 and vowelmsg.msg_e = 1 so an unchecked
>> conversion is wrong on so many levels.
>
> Yes, this may be worse, but you can at least get Unchecked_Conversion
> to work:
>
> for Vowelmsg use (Msg_A => 0, Msg_E => 4);
> for Vowelmsg'Size use Msg'Size;
>
> This would still be a run-time check:...
For run-time I find the "Value of Image" idiom a better one. It's
readily available. No Unchecked_Conversion required.
declare
M : Msg := Whatever;
V : Vowelmsg;
begin
V := Vowelmsg'Value (Msg'Image (M));
-- if control reaches here then M is a vowel
exception
when Constraint_Error => -- M is not a vowel
end;
next prev parent reply other threads:[~2005-02-02 17:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-01 23:51 Why can't you create a out of order subtype? brett_gengler
2005-02-02 0:24 ` Jeffrey Carter
2005-02-02 17:55 ` Marius Amado Alves [this message]
2005-02-02 18:50 ` Pascal Obry
2005-02-02 20:22 ` Marius Amado Alves
2005-02-03 4:36 ` Wes Groleau
2005-02-03 12:59 ` Marius Amado Alves
2005-02-04 3:42 ` Wes Groleau
2005-02-02 19:35 ` Martin Dowie
2005-02-02 20:35 ` Marius Amado Alves
2005-02-02 21:18 ` Martin Dowie
2005-02-03 19:40 ` Robert A Duff
2005-02-03 20:22 ` Marius Amado Alves
2005-02-03 22:05 ` Robert A Duff
2005-02-04 6:49 ` Martin Dowie
2005-02-02 22:26 ` Georg Bauhaus
2005-02-03 23:09 ` Robert A Duff
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