From: "G.B." <bauhaus@futureapps.invalid>
Subject: Re: Declaring constants for a abstract tagged type and concrete sub classes
Date: Mon, 6 Jul 2015 13:55:01 +0200
Date: 2015-07-06T13:55:01+02:00 [thread overview]
Message-ID: <mndq80$h9m$1@dont-email.me> (raw)
In-Reply-To: <0ade6abf-34c0-46e2-8bd9-d60a00056321@googlegroups.com>
On 06.07.15 12:10, Serge Robyns wrote:
> package Abstract_Root is
> type T_Root is abstract tagged with private;
> procedure Set_XYZ (Self: in out T_Root; ABC : in Integer);
> function Get_XYZ (Self: in T_Root) return Integer;
> private
> type T_Root is abstract tagged record
> XYZ : Integer;
> end record;
> end Abstract_Root;
In case you can afford a publicly abstract but
privately non-abstract type,
package Abstract_Root is
type T_Root is abstract tagged private;
procedure Set_XYZ (Self: in out T_Root; ABC : in Integer);
function Get_XYZ (Self: in T_Root) return Integer;
No_Element : constant T_Root; -- or T_Root'Class;
private
type T_Root is tagged record
XYZ : Integer;
end record;
No_Element : constant T_Root := T_Root'(Xyz => 666);
end Abstract_Root;
Every object needs to be of a concrete type, whether constant
or not.
If what is wanted is some information about any object
in T_Root'Class (its derivation hierarchy), such as
being a "special" object acting as "no object", say,
a function (to override) might do.
next prev parent reply other threads:[~2015-07-06 11:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-06 10:10 Declaring constants for a abstract tagged type and concrete sub classes Serge Robyns
2015-07-06 11:55 ` G.B. [this message]
2015-07-06 13:49 ` Serge Robyns
2015-07-06 17:36 ` G.B.
2015-07-07 16:27 ` Serge Robyns
2015-07-07 17:21 ` G.B.
2015-07-07 19:51 ` Serge Robyns
2015-07-07 20:14 ` Simon Wright
2015-07-07 20:18 ` Jeffrey R. Carter
2015-07-06 15:42 ` Simon Wright
2015-07-06 16:35 ` Serge Robyns
2015-07-06 17:02 ` Bob Duff
2015-07-06 21:16 ` Serge Robyns
2015-07-06 17:30 ` gautier_niouzes
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