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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Access types as parameters
Date: Mon, 20 Jul 2009 19:34:56 -0500
Organization: Jacob Sparre Andersen
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Date: 2009-07-20T19:34:56-05:00
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"rickduley" <rickduley@gmail.com> wrote in message 
news:e325296c-7114-4540-9406-b7426da408dd@f18g2000prf.googlegroups.com...
> 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?
>
> It actually uses the form (this for Gtk.Button.Gtk_Button):
> procedure Initialize
>  (Button : access Gtk_Button_Record'Class;
>   Label  : UTF8_String);

You'd have to ask the designers of GTKAda that question. I think it's 
terrible to define Ada-level interfaces that way, but they may have had good 
reasons. See Claw 
(http://www.rrsoftware.com/html/prodinf/claw/clawintro.html for the free 
version) to see how I think a real-world Ada GUI library ought to be 
designed. (Well, more accurately, how I thought 10 years ago, I'd make some 
minor changes today, mainly making most of the types limited, as that works 
much better in Ada nowadays).

                                     Randy.


                                     Randy.