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!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Predefined Language Attributes 'ADDRESS and 'ACCESS Date: Thu, 6 Dec 2018 10:56:07 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <5c08c0d3$0$7083$e4fe514c@news.kpn.nl> NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.2 X-Notice: Filtered by postfilter v. 0.8.3 Content-Language: en-US Xref: reader01.eternal-september.org comp.lang.ada:54974 Date: 2018-12-06T10:56:07+01:00 List-Id: On 2018-12-06 07:25, ldries46 wrote: > What is the principal difference between the Attributes 'ADDRESS and > 'ACCESS? When do you use them? 1. Access is portable, Address is not. However across machines with flat memory Address might be as good as portable. 2. Access is strongly typed, Address is untyped. Furthermore access supports dispatching and class-wide calls as expected. 3. Access is memory pool aware, Address is blind to whatever memory management policy. 4. Access could work around some machine limitations address cannot. E.g. access could, theoretically, refer to things that do not have physical address, like packed data, data outside conventional memory etc. 5. Access is a subject of accessibility checks and other constraints, e.g. "not null". Not everybody sees all these as an advantage, but in some cases it might help to generate safer and more efficient code. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de