From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!nntp-feed.chiark.greenend.org.uk!ewrotcd!newsfeed.xs3.de!io.xs3.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED.rrsoftware.com!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Comparing Access Types
Date: Tue, 21 Nov 2017 19:01:10 -0600
Organization: JSA Research & Innovation
Message-ID: <ov2i8m$i8p$1@franka.jacob-sparre.dk>
References: <b3976d73-296f-4958-bfb2-26bf49901a48@googlegroups.com>
 <ou13tc$2de$1@gioia.aioe.org> <wccpo8rjcwg.fsf@TheWorld.com>
 <ou3obs$o2n$1@gioia.aioe.org> <wcc8tfejezt.fsf@TheWorld.com>
 <wccinei14g6.fsf@TheWorld.com> <ouiovq$g6l$1@franka.jacob-sparre.dk>
 <wcclgj3z1of.fsf@TheWorld.com> <ouvkpa$9ai$1@franka.jacob-sparre.dk>
 <0709f97b-a32c-41c6-9e5d-ccabaae14274@googlegroups.com>
 <ov0pp1$1rlu$1@gioia.aioe.org>
Injection-Date: Wed, 22 Nov 2017 01:01:10 -0000 (UTC)
Injection-Info: franka.jacob-sparre.dk;
 posting-host="rrsoftware.com:24.196.82.226";
	logging-data="18713"; mail-complaints-to="news@jacob-sparre.dk"
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Response
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.7246
Xref: feeder.eternal-september.org comp.lang.ada:49043
Date: 2017-11-21T19:01:10-06:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:ov0pp1$1rlu$1@gioia.aioe.org...
...
>> it's pretty much purpose-built to do that (it's in the name, after all).
>
> It has a nasty issue that you cannot pass your own access type. It is 
> clear that not any access type could be acceptable. The implementation 
> should be free to reject some upon instantiation.

Bob apologies for that nearly every time the subject comes up. (Not sure if 
he will do it here...) It is generally acknowledged to be a mistake; any 
general access type with convention Ada ought to work, and that is easily 
modeled with a generic formal access type. Having the type declared in the 
instance is a pain. It's not quite the pain than many think it is, since one 
can use a type conversion from the type declared in the instance to any 
other general access type with the right convention and designated type. But 
all of those extra conversions are just noise, and add nothing to program 
readability or understandability.

                                              Randy.