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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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Newsgroups: comp.lang.ada
Subject: Re: Discriminants of tagged types
Date: Thu, 28 Oct 2010 19:48:50 +0200
Organization: Ada @ Home
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Date: 2010-10-28T19:48:50+02:00
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Le Thu, 28 Oct 2010 10:50:51 +0200, Maciej Sobczak  =

<see.my.homepage@gmail.com> a =C3=A9crit:
>> This has nothing to do with copying. Consider a handle of a resource,=
  =

>> e.g.
>> HWND as an example. It is bound to the resource, nevertheless it is
>> copyable.
>
> [...]
> What would it mean to copy a file object? Should the file on disk be
> copied as well? Should the data that is still in the buffer be copied?=

> And so on. Instead of answering these questions in an unsatisfactory
> way, it is better to outlaw the dubious operation up front.
Proxy objects needs not to be all the same. At least the Windows API do =
 =

this (as others OS do) : you may open a file multiple times, get multipl=
e  =

handles to it, with for each, different access rights. The handle is not=
  =

the file, this is a kind of proxy to a file's physical instance. The  =

application on its own side, may do the same with handles, and hide file=
  =

handles behind proxies (two levels). This is even a common construct, as=
  =

in most designs you have references, smart references and proxies allove=
r  =

the place.

You obviously have the same with object whose intent is to draw on the  =

screen.

May be this is too much wide to be uniquely identified and when the  =

concept is referred to, it finally just tell few (and that's what may ma=
ke  =

its exact intent smoggy).

-- =

Si les chats miaulent et font autant de vocalises bizarres, c=E2=80=99es=
t pas pour  =

les chiens.