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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Your wish list for Ada 202X
Date: Sat, 19 Apr 2014 16:53:47 +0300
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:19415
Date: 2014-04-19T16:53:47+03:00
List-Id: <comp.lang.ada>

On 14-04-19 13:06 , Dmitry A. Kazakov wrote:
> On Sat, 19 Apr 2014 12:08:19 +0300, Niklas Holsti wrote:
> 
>> On 14-04-19 11:39 , Dmitry A. Kazakov wrote:
>>> On Sat, 19 Apr 2014 10:19:02 +0200, Dmitry A. Kazakov wrote:
>>>
>>>> "Re-" presumes that dispatch happens again. What is in common to these two
>>>> instances of dispatch what makes it re-dispatch? It is 1) the same
>>>> polymorphic operation and 2) the same object. Take either away and it is
>>>> not re-dispatch anymore:
>>>>
>>>> 1. Different operations:
>>>>
>>>>    X.Foo;
>>>>    X.Bar;  -- This is not re-dispatch!
>>>>
>>>> 2. Different objects:
>>>>
>>>>    X.Foo;
>>>>    Y.Foo;  -- This is not re-dispatch!
>>>
>>> After some consideration, I take the position 1 back. Operation can be
>>> different. But the object must be same.
>>
>> If we are talking about by-copy types, then whether X and Y are the
>> "same object" is fuzzy. Is a copy the same object as the original?
> 
> A copy is another object.

Then (by your definitions) redispatching is never possible based on
by-copy parameters, because (in your definition) redispatching only
occurs if the first and second dispatching call use the same object, but
the pass-by-copy in the first dispatching call (in your view) creates a
new object which is then used in the second dispatching call.

That is a consistent view (good for you) but it disagrees with my memory
of your earlier arguments against redispatching, which were based more
on the logical redundancy of two successive dispatching calls on the
same tag.

>> In some logical sense it is, in a physical sense it isn't.
> 
> The reverse. It might be logically same, when "=" yields true and
> physically different.

That's what I said, logically the same, physically not. You misread my
last sentence.

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