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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Smart Pointers and Tagged Type Hierarchies
Date: Wed, 2 Aug 2017 14:26:41 -0500
Organization: JSA Research & Innovation
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Date: 2017-08-02T14:26:41-05:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:olrreq$1tp3$1@gioia.aioe.org...
> On 2017-08-02 00:41, Randy Brukardt wrote:
>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
>> news:olpb12$1o3$1@gioia.aioe.org...
>>> On 2017-08-01 05:43, Randy Brukardt wrote:
>> ...
...
> Same as above. The 2-D table is:
>
>    A1 A2 A3
> B1  *
> B2     *
> B3        *
>
> You do exactly same thing. You check if you are on the diagonal, then you 
> dispatch using any of two tags once. Just one hop.

That's how interfaces work, essentially. They are very difficult to 
implement efficiently (I believe it is impossible in general). I 
(personally) don't want more interface like implementation complication. 
(It's unlikely that Janus/Ada will ever implement interfaces for this 
reason.)

                                  Randy.