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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada package registry?
Date: Mon, 8 Feb 2016 17:02:18 -0600
Organization: JSA Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:29447
Date: 2016-02-08T17:02:18-06:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:n94cbv$19ed$1@gioia.aioe.org...
> On 2016-02-06 01:04, Randy Brukardt wrote:
>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
>> news:n91oau$1bk5$1@gioia.aioe.org...
>>> On 04/02/2016 22:09, Randy Brukardt wrote:
>> ....
>>>> (The reason that we adopted the generalized reference feature that we 
>>>> did
>>>> is
>>>> because of the ability to use it to manage persistence -- in 
>>>> particular,
>>>> to
>>>> be able to figure out when the in-memory copy can be freed and written 
>>>> to
>>>> the backing store.)
>>>
>>> That is not enough. You need references with a notification upon
>>> dereferencing.
>>
>> That's called "a function call" :-). There's no need for a separate 
>> feature
>> for that (since anonymous access results are essentially uncopyable). 
>> What
>> was missing was a way to know when the access itself goes away.
>
> That is called a function call too.

Well, actually a procedure call (to Finalize).

> For persistence layer you need dereference primitive operations. One for 
> read access in order to cache data and one write access to mark the cache 
> dirty.

The first is the function call (to Reference, if you're looking at the Ada 
containers), and the second is the Finalize call that happens when the 
object returned from Reference goes away. That was the whole point of the 
design. (Of course, you could have written that in Ada 95, but without the 
syntactic sugar that makes it easier to read and write.)

                                   Randy.