From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!aioe.org!5WHqCw2XxjHb2npjM9GYbw.user.gioia.aioe.org.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Performance of records with variant parts Date: Mon, 22 Mar 2021 19:07:03 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <07a56dcc-9e17-49b2-a980-3a5a2d265cedn@googlegroups.com> NNTP-Posting-Host: 5WHqCw2XxjHb2npjM9GYbw.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; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 X-Notice: Filtered by postfilter v. 0.9.2 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:61635 List-Id: On 2021-03-22 18:45, John Perry wrote: > On Monday, March 22, 2021 at 12:39:54 PM UTC-5, Dmitry A. Kazakov wrote: >> On 2021-03-22 18:02, John Perry wrote: >> >>> Is there a reason that the record with variant parts runs so much slower? I can make the complete source available if need be. >> It must check the discriminant if the object is dynamically constrained. > > I'm not quite sure I understand. Are you saying that it has to check the discriminant at run-time? Yes, if the field is in the variant part and the discriminant cannot be statically deduced to indicate that part [or not, so that it could always raise Constraint_Error] > How would that differ from checking the value if it were merely a field of the record? The field is always there. I think if you made it an Unchecked_Union you would have no penalty (and no safety). -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de