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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Access to function returning class-wide type
Date: Thu, 21 Aug 2008 23:53:10 -0500
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Date: 2008-08-21T23:53:10-05:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:tslrrr8w3j63.zp28ykzgmr23.dlg@40tude.net...
...
> P.S. I don't know reasons why it was decided to use an access type in
> Ada.Tags.Generic_Dispatching_Constructor profile. One could always pass a
> pointer there if a side effect on the parameters were desired. But that is
> another issue, and in any case Proc is thought as an implementation 
> detail,
> so its exact profile should not really matter.

I originally came up with this proposal (based on random thoughts tossed out 
by Steve Baird and Tucker Taft). We'd been trying to find solutions for 
literally years; I was amazed that this one didn't fall into a heap of slag 
as the others had.

Anyway, the access parameter exists so that an instance of this routine 
matches the profile of S'Class'Input. After all, the purpose of this routine 
is to eliminate the Ada 95 compiler magic involved with S'Class'Input and 
make it user-programmable. The thought is that a user-defined version of 
S'Class'Input would be directly specified as an instance of 
Generic_Dispatching_Constructor.

In hindsight, I'm not certain that is a good idea, because it mucks up the 
spec for no particularly good reason. But that's the way it is now.

                                                   Randy.