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!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!newsfeed.kamp.net!newsfeed.kamp.net!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Niklas Holsti Newsgroups: comp.lang.ada Subject: Re: Overriding puzzle Date: Thu, 31 Dec 2015 10:22:01 +0200 Organization: Tidorum Ltd Message-ID: References: <5be84c5a-9614-4ee2-ae85-beb962171a05@googlegroups.com> <192c4493-9c53-4e23-b9bd-e4c543738dbc@googlegroups.com> <26e20ae9-ad86-4c88-9c67-f1a4a9b33f23@googlegroups.com> <677d0956-63d3-4de8-a6e5-b79c52a1dc12@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net BIFhpWyEaf4aYt1ynQjPkwnwhnsfnVARE7gztrZm8g0m7es4Hc Cancel-Lock: sha1:lXnki/uVjUM36hPfv1oBVX1P7Is= User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 In-Reply-To: Xref: news.eternal-september.org comp.lang.ada:28948 Date: 2015-12-31T10:22:01+02:00 List-Id: On 15-12-31 01:10 , Randy Brukardt wrote: > wrote in message > news:677d0956-63d3-4de8-a6e5-b79c52a1dc12@googlegroups.com... >> On Wednesday, December 30, 2015 at 1:24:06 PM UTC-5, >> gautier...@hotmail.com wrote: >>> No, the "A'Class(o)" also makes the difference when type Custom >>> is framed into a package: >> > ... >> General note to self: tagged type operations that call other operations of >> the type should always(?) convert the object to its 'class so as to cause >> dispatching. Not doing so is probably a defect! > > Nooooo. Redispatching is best left for very limited circumstances. There's a > reason that Ada makes you write it explicitly! Close to an extreme view, in the spectrum of views... But I agree that it is good that Ada requires an explicit indication of redispatching. > The model of Ada is that within a routine (including inherited routines) the > object acts as if it had the named type. This makes it much easier to reason > about the routine, as the behavior of all of the routines called is known. > > When you redispatch, you no longer can reason in any useful way about the > behavior of the call -- essentially you are depending on "magic" (and the > competency of others) to get the right answer. In limited circumstances > (like the OP), it works well, but for general programming, look out! The same (IMO a bit paranoid) argument would logically apply to all dispatching calls, including dispatching calls from class-wide subprograms. The conclusion would be that one cannot reason in any useful way about any dispatching call. I don't agree with that conclusion. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ .