From: stefan-lucks@see-the.signature
Subject: Re: What makes a procedure call 'dispatching' in Ada?
Date: Fri, 20 Nov 2009 10:31:38 +0100
Date: 2009-11-20T10:31:38+01:00 [thread overview]
Message-ID: <Pine.LNX.4.64.0911201018540.19682@medsec1.medien.uni-weimar.de> (raw)
In-Reply-To: <he64pl$d8i$1@nntp.ilk.net>
If Foo is a tagged type, then
"procedure A(This: [in] [out] Foo)"
expects *exactly* the same type as the actual parameter. If you want
"either type Foo or any of its object-oriented children" you write
"procedure B(This: [in] [out] Foo'Class)".
In your case, Foo is an abstract tagged type. As much as I seem to
understand Ada, there is no way to actually call procedure A -- because
you can't have any actuals of an abstract type. (Hey you guys out there,
am I wrong?)
If I am right, it is very regrettable that the compiler doesn't issue a
warning when compiling "procedure A(This: [in] [out] Foo)" for an abstract
type Foo ... perhaps better, a revised Ada should prohibit that.
So long
Stefan
On Fri, 20 Nov 2009, Markus Schoepflin wrote:
> ---%<---
> package FOOS is
>
> type FOO is abstract tagged null record;
>
> procedure P (THIS : in FOO);
-------> replace by
procedure P (THIS : in FOO'Class);
> procedure A (THIS : in FOO) is abstract;
>
> end FOOS;
>
> package body FOOS is
>
> procedure P (THIS : in FOO)
-------> replace by
procedure P (THIS : in FOO'Class);
> is
> begin
> A (THIS);
> end;
>
> end FOOS;
> --->%---
>
> When trying to compile this, I get:
>
> foos.adb:6:07: call to abstract function must be dispatching
> gnatmake: "foos.adb" compilation error
>
> What is the compiler trying to tell me here? And how do I go about calling
> abstract procedures?
>
> TIA,
> Markus
>
--
------ Stefan Lucks -- Bauhaus-University Weimar -- Germany ------
Stefan dot Lucks at uni minus weimar dot de
------ I love the taste of Cryptanalysis in the morning! ------
next prev parent reply other threads:[~2009-11-20 9:31 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-20 13:15 What makes a procedure call 'dispatching' in Ada? Markus Schoepflin
2009-11-20 9:31 ` stefan-lucks [this message]
2009-11-20 14:10 ` Niklas Holsti
2009-11-20 13:27 ` Dmitry A. Kazakov
2009-11-20 13:43 ` Markus Schoepflin
2009-11-20 13:54 ` RasikaSrinivasan@gmail.com
2009-11-20 13:58 ` Markus Schoepflin
2009-11-20 14:19 ` Niklas Holsti
2009-11-21 14:07 ` Peter C. Chapin
2009-11-20 14:00 ` Niklas Holsti
2009-11-20 14:10 ` Dmitry A. Kazakov
2009-11-20 13:56 ` Niklas Holsti
2009-11-20 14:31 ` Dmitry A. Kazakov
2009-11-20 15:00 ` Niklas Holsti
2009-11-20 18:44 ` Dmitry A. Kazakov
2009-11-20 20:09 ` Niklas Holsti
2009-11-20 20:59 ` Dmitry A. Kazakov
2009-11-20 14:54 ` Ludovic Brenta
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