From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Type of the target of an assignment shall not be abstract
Date: Sun, 14 Feb 2010 18:57:48 +0100
Date: 2010-02-14T18:57:40+01:00 [thread overview]
Message-ID: <qjm4z3u0gdun.omqnep7wy8de.dlg@40tude.net> (raw)
In-Reply-To: 770863d9-14ae-4a05-b924-2dfeda7a96a8@f15g2000yqe.googlegroups.com
On Sun, 14 Feb 2010 06:20:32 -0800 (PST), Gautier write-only wrote:
> A question for the RM hermeneutists.
> The instruction marked below with ">>>" goes well through one Ada 95
> compiler (GNAT with -gnat95) but is not accepted by another one
> (ObjectAda 7.2.2).
> Which compiler is right ?
>
> procedure Init(
> xl : in out Excel_Out_Stream'Class;
> format : Excel_type:= Default_Excel_type
> )
> is
> dummy_xl_with_defaults: Excel_Out_File;
> begin
> -- Check if we are trying to re-use a half-finished object
> (ouch!):
> if xl.is_created and not xl.is_closed then
> raise Excel_Stream_Not_Closed;
> end if;
> dummy_xl_with_defaults.format:= format;
>>>> Excel_Out_Stream(xl):= Excel_Out_Stream(dummy_xl_with_defaults);
> end Init;
>
>>>> excel_out.adb: Error: line 595 col 5 LRM:3.9.3(8), The type of the target of an assignment shall not be abstract
>
> For those asking themselves what the *@#$! that code is doing, since
> the xl variable is already initialized, the purpose of the := is to re-
> initialize an object (xl) with the default values of the root type.
> Since the root type is abstract, I need a concrete derived object
> (dummy_xl_with_defaults) to get these default values. Subsidiary
> question: is there another way of doing that in one ':=' ?
package P is
type T is abstract tagged private;
procedure Reset (X : in out T'Class);
private
type Root is tagged record -- Non-abstract
I : Integer;
end record;
type T is abstract new Root with null record;
end P;
package body P is
Defaults : Root := (I => 123);
procedure Reset (X : in out T'Class) is
begin
Root (X) := Defaults;
end Reset;
end P;.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2010-02-14 17:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-14 14:20 Type of the target of an assignment shall not be abstract Gautier write-only
2010-02-14 17:57 ` Dmitry A. Kazakov [this message]
2010-02-15 17:05 ` Adam Beneschan
2010-02-15 19:00 ` Hibou57 (Yannick Duchêne)
2010-02-23 21:19 ` Robert A Duff
2010-02-16 0:59 ` Adam Beneschan
2010-02-16 10:03 ` Gautier write-only
2010-02-16 12:14 ` Gautier write-only
2010-02-16 16:12 ` Adam Beneschan
2010-02-28 17:00 ` Gautier write-only
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