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: SPARK: missing case value Date: Fri, 9 Oct 2015 17:10:18 +0200 Organization: cbb software GmbH Message-ID: References: <87twq09ke2.fsf@theworld.com> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: j6IQVb9uobzjXrpQLDU2rQ.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:27949 Date: 2015-10-09T17:10:18+02:00 List-Id: On Fri, 09 Oct 2015 10:39:01 -0400, Bob Duff wrote: > But this works: > > type Enum is (A, B, C); > subtype A_C is Enum with Predicate => A_C /= B; > > procedure Test (E : in A_C) is > begin > case E is > when A => null; > -- "when B" is not needed. > when C => null; > end case; > end Test; > > And that has the advantage that A_C need not be a subrange; > it can have holes. > > I find that predicates are often better than preconditions, > because the same precondition often applies to many parameters, > and also to local variables. The predicate allows you to avoid > repetition. Because the above is a proper contract, while precondition is a land mine. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de