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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Your wish list for Ada 202X
Date: Wed, 16 Apr 2014 09:32:15 +0300
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:19328
Date: 2014-04-16T09:32:15+03:00
List-Id: <comp.lang.ada>

On 14-04-15 10:21 , Natasha Kerensikova wrote:
> Hello, 

  [snip]

> let's consider an abstract type T, with an abstract operation AO and a
> huge part of the algorithm implemented in primitive operations for T,
> making use of AO. Concrete descendants of T are supposed to implement
> AO, and inherit the rest without overriding.
> 
> Then in T subprograms I end up with things that look like:
>    AO (T'Class (Self), Other, Arguments);
> 
> 
> I've always thought of this as "re-disatching". Is it?

Yes, as I understand the word.

> Are there better language facilities to use in such situations?

If, as you say above, descendants of T are supposed to inherit the
primitive operations of T *without overriding them*, you could implement
those primitive operations instead as class-wide operations (operations
on T'Class), and then calls of AO from those class-wide operations would
be (simply) dispatching, and not re-dispatching.

As I understand them, both Dmitry and Randy would consider the
class-wide form a better solution, but it works only if you never need
to override these class-wide operations for any descendant types.

I am seldom sure about that (never needing to override, not even in the
future), so I prefer to have the operations as primitive rather than
class-wide, and consequently to use re-dispatch.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .