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Subject: Re: GtkAda : Trying to derive a widget
Newsgroups: comp.lang.ada
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From: DrPi <314@drpi.fr>
Date: Fri, 9 Apr 2021 15:37:50 +0200
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Le 09/04/2021 à 14:23, Dmitry A. Kazakov a écrit :
> On 2021-04-09 13:42, DrPi wrote:
>> Le 09/04/2021 à 08:18, Dmitry A. Kazakov a écrit :
> 
>>> Debug_Panel belongs to both Debug_Panel_Record'Class and 
>>> Gtk_Scrolled_Window_Record'Class (and many other classes), so the 
>>> ambiguity.
>>>
>> Surprising behaviour for a strongly typed language but there surely is 
>> a good reason.
> 
> It is strongly typed.
> 
> The class is defined a set of types closed upon inheritance. When you 
> declare a class-wide operation like Initialize it is meant to work on 
> all instances of the class. There is no type violation or type coercion 
> here.
> 
> Initialize of Gtk_Scrolled_Window_Record'Class is defined on 
> Gtk_Scrolled_Window_Record and all types derived from 
> Gtk_Scrolled_Window_Record.
> 
> When you declare another Initialize on Debug_Panel_Record'Class it is 
> defined on Debug_Panel_Record and all its descendants.
> 
> If you overload them, in a context you must disambiguate for 
> Debug_Panel_Record and any descendant of.
> 
> This is not different from Ada subtypes. For example, you can declare
> 
>    procedure Foo (I : Integer);
> 
> and in some other package
> 
>    procedure Foo (I : Positive);
> 
> If both become visible in a context you would have same problem.
> 

Ok.
Thanks for clarifying.