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From: Ivan Levashev <bu_gen@octagram.name>
Newsgroups: comp.lang.ada
Subject: Re: Smart Pointers and Tagged Type Hierarchies
Date: Thu, 27 Jul 2017 00:53:01 +0700
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Xref: news.eternal-september.org comp.lang.ada:47515
Date: 2017-07-27T00:53:01+07:00
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24.07.2017 22:41, Felix Krause пишет:
> * A derived type, if it wants to provide additional operations (like
> Current_Position), must not only derive from Instance, but also from
> Reference, to be able to provide an type-safe interface to those
> operations.

My approach is to have independent (mutually noncastable) reference 
types and explicit upcast/downcast functions.

You can either copy all parent's methods by hand or use generic mix-ins 
to add methods to proto-reference-types for every reference type.

Also, tricks with Ada 2012 references can save Adjust/Finally calls. As 
soon as references don't have dispatching, tag is useless, so it can 
overlap with Ada 2012 reference's access discriminant.

Best Regards,
Ivan Levashev,
Barnaul

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