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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ada Successor Language
Date: Fri, 29 Jun 2018 09:20:38 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:53423
Date: 2018-06-29T09:20:38+02:00
List-Id: <comp.lang.ada>

On 2018-06-29 05:11, Paul Rubin wrote:
> "Dan'l Miller" <optikos@verizon.net> writes:
>> bad idea that threatens to bring C++ slicing to Ada
> 
> Are you talking about this?
> 
>     https://en.wikipedia.org/wiki/Object_slicing
> 
> Does Ada somehow escape from it now?

Sure, there is no way to reconstruct that in Ada.

> It does sound bad.

Only due to C++ design fault. Assignment is a classic multiple dispatch 
operation (a multi-method). C++ per design does no support MD. Here you go.

With MD it is no more an issue. Let T and S be two types T <: S. The 
assignment operation of mixed arguments and result

    ":=" : S x T -> S

could not be safely inherited by S from T's:

    ":=" : T x T -> T

Therefore the compiler would ask the programmer to override it (or 
redesign). Problem solved.

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