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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ada Successor Language
Date: Mon, 25 Jun 2018 16:21:57 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:53301
Date: 2018-06-25T16:21:57+02:00
List-Id: <comp.lang.ada>

On 2018-06-25 16:03, Niklas Holsti wrote:

> (In fact, it seems to me that Ada could allow untagged record extensions 
> as well; the effect would be the same as for tagged ones, but no 'Class 
> would be formed, and no class-wide programming or dynamic dispatch could 
> be used, so all such types would be static.

Ada could allow T'Class for untagged T. T'Class would be an indefinite 
type with values consisting of the actual type's tag and its value. When 
T is by-value type, you pass T'Class to a subprogram as tag + value. 
When T is by-reference type, you pass tag + reference.

Upon dispatch, you strip the tag from the value or reference before 
passing value/reference down.

P.S. No re-dispatch is possible in this model, sorry.

P.P.S. Tagged type is a special case when T and T'Class have same 
representation.

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