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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada)
Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
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Date: Tue, 15 Mar 2005 09:59:57 +0100
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Date: 2005-03-15T09:56:27+01:00
List-Id: <comp.lang.ada>

On Tue, 15 Mar 2005 00:10:27 GMT, Dr. Adrian Wrigley wrote:

> On Mon, 14 Mar 2005 23:46:33 +0000, Hyman Rosen wrote:
> 
>> Dr. Adrian Wrigley wrote:
>>> This means that you can't write an implementation of a template/generic
>>> function using a map/hash without changing some/all the implementations
>>> and interfaces up the instantiation tree (am I right?).
>> 
>> No, you are wrong. Simply write your comparison or hash function at the
>> point where you need it. Use the public accessors to get the data you
>> need to perform the operations.
> 
> That's the point... there aren't any public accessor functions
> for opaque data types such as non-limited generic formal parameters.

Then the data are inherently non-sortable. That was designer's decision,
and that is *the* contract. To define "<" would mean to break that
contract.

There are lot of situations where some ad-hoc generated comparison will not
work. Especially if objects are in fact handles to something that may
change asynchronously to the container.

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