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From: "John B. Matthews" <nospam@nospam.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Access types as parameters
Date: Sun, 19 Jul 2009 20:10:01 -0400
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Date: 2009-07-19T20:10:01-04:00
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In article 
<e325296c-7114-4540-9406-b7426da408dd@f18g2000prf.googlegroups.com>,
 rickduley <rickduley@gmail.com> wrote:

> Hi Randy
> 
> You wrote:
> > So it is best to avoid the first form unless you have a particular need for
> > dispatching on an access value (which won't happen here, because the
> > designated type is class-wide).
> 
> Why then does GtkAda consistently use the first form, i.e.:
> function My_Function (Thing : access My_Type'Class) return Positive;
> for an 'Initialize' function?

IIUC, "Thing" typically points to an object managed by the Gtk library. 
It's outside the scope of Ada's accessibility rules.

> It actually uses the form (this for Gtk.Button.Gtk_Button):
> procedure Initialize
>   (Button : access Gtk_Button_Record'Class;
>    Label  : UTF8_String);

The source mentions the section "Creating your own widgets" in the 
user's guide. The section "Creating new widgets in Ada" addresses the 
Initialize procedure explicitly:

<http://libre.adacore.com/wp-content/files/auto_update/gtkada-docs/
gtkada_ug/gtkada_ug.html>

-- 
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>