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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: basic basic ada question
Newsgroups: comp.lang.ada
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Date: Tue, 24 Oct 2006 09:34:59 +0200
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Date: 2006-10-24T09:34:59+02:00
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On Mon, 23 Oct 2006 11:49:17 -0400, Robert A Duff wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> type T is abstract ...;
>> function Greeting_Message return String is abstract;
> 
> I presume the above is supposed to say (X : T), right?

Yes, my fault.

> If so, I don't see anything illegal here.

OK, I didn't specifically mean Ada.

As for Ada if Initialize were a declared part of the default constructor,
then view conversions to the class could be statically detected and made
illegal. Though, I would consider to disallow them for the types to replace
present tagged types. I mean the types with the type tag stored in the
objects. For the tag-less types it not a problem, because T'Class would
create a new object constructed through a copy constructor.

>> procedure Initialize (X : in out T) is
>> begin
>>    Put_Line ("Hi," & Greeting_Message (T'Class (X))); -- Illegal!
>> end Initialize;
>>
>> type S is new T with ...;
>> function Greeting_Message return String is
>> begin
>>    return "I am T!";
>> end Greeting_Message;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de