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=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no 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!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: function Is_Open (File : File_Type) return Boolean; :Text_io Date: Tue, 27 Oct 2015 09:30:16 +0100 Organization: cbb software GmbH Message-ID: <1pj15r7pul7f1.15qgdyrc8k133$.dlg@40tude.net> References: <87twpd2qlo.fsf@theworld.com> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: TWQ9mg4k1m/sph/eQ+zHLA.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:28066 Date: 2015-10-27T09:30:16+01:00 List-Id: On Mon, 26 Oct 2015 18:48:51 -0400, Bob Duff wrote: > comicfanzine@gmail.com writes: > >> Can someone please show my a code in which this function is used , i'm >> lost , thanks . > > Most code is written so that it is statically known whether a file is > open, so Is_Open is close to useless. Not entirely useless -- you might > use it in an assertion, such as: > > subtype Open_File is File with Predicate => Is_Open(Open_File); In order to have the Constraint_Error exception instead of Status_Error? Looks entirely useless to me. > And Niklas Holsti gave a fairly realistic example where it is NOT > statically known whether the file is open, so the program checks at run > time. Yes, but you cannot put a constraint on an existing object. Thus Niklas example does not apply. [ Dynamic predicates never make any sense. ] -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de