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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ada Annoyances
Date: Thu, 22 Jun 2017 09:29:20 +0200
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Date: 2017-06-22T09:29:20+02:00
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On 22/06/2017 00:45, pythoner6@gmail.com wrote:
> On Wednesday, June 21, 2017 at 12:12:53 PM UTC-4, Dmitry A. Kazakov wrote:
>> In Ada there is no penalty of calling a "method" vs. a "free" function.
>> None, whatsoever. This per language type system design and different
>> from C++.
> 
> I would say the same is true of C++

In C++ calls to a method go through the virtual table. In Ada they never 
do because Ada is strongly typed. This gives you performance and type 
safety (LSP stuff etc) upon inheritance. Re-dispatch is evil from SW 
design POV.

> Thanks for the clarifications - as mentioned in my previous post, I
> think the main misconception I had was about when dynamic dispatch
> happens: I rather naively assumed that dynamic dispatch happened
> whenever tagged types were involved.
It is controlled by the type, because see above, Ada is properly typed. 
The dispatch never happens on a tagged type T. It always do on a 
class-wide type T'Class, which is not tagged. T /= T'Class.

> After reading this it sounds like using tagged types in Ada is quite
> similar to dealing with classes in C++ (i.e. in C++, methods have the
> implicit this parameter which is also only ever passed by reference).

Not so much similar, C++ type system is broken in that respect. C++ does 
not distinguish T and T'Class. Semantically C++ class type is sometimes 
one and sometimes another. E.g. in a constructor or destructor it acts 
as T. Elsewhere it does as T'Class.

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