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!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Ada 2012 Constraints (WRT an Ada IR) Date: Tue, 13 Dec 2016 09:27:57 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <47366b42-c0a3-41bf-a44a-5241c109d60f@googlegroups.com> NNTP-Posting-Host: vZYCW951TbFitc4GdEwQJg.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 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:32774 Date: 2016-12-13T09:27:57+01:00 List-Id: On 13/12/2016 08:15, G.B. wrote: > On 12/12/2016 21:53, Dmitry A. Kazakov wrote: >> On 2016-12-12 19:55, G.B. wrote: >>> On 12/12/2016 18:39, Dmitry A. Kazakov wrote: >>>> As I said before it must be moved to the post-condition, >>>> Storage_Error, or whatever raised upon stack overflow included. >>> >>> Could you please show a good Post aspect for >>> >>> function Plus_Too (A, B: Standard.Integer) >>> return Standard.Integer is >>> begin >>> return A + B; >>> end Plus_Too; >> >> None. Don't use aspects they are not good. I have already listed >> post-conditions, see my post from 2016-12-09. > > No Ada in there. I was thinking of this posting. Ada is an object language here. Thus it can never be Ada. It could be a meta language of annotations for Ada, like SPARK. > So, is there nothing we can say about the arguments > when we declare Plus_Too, such as how they need to be > related for Plus_Too at all having a chance of not raising? > >> Implied contracts are outside the scope. > > My point. Why should contracts not be explicit, in particular > when they had already been formal, albeit in a comment? Explicit contracts are only ones the framework can enforce, at all or pragmatically. Anything it cannot goes into the "implicit" bin. >> There is an infinite number of implied contracts which can be violated, >> e.g. the one that the Earth does not turn black hole... > > That's curious. Can you show us the contract written and explicitly > stating that the Earth does not turn black hole, and then explain > how a programmer writing a call can violate this contract? It is an explicit contract. The contract gets violated when the Plus_Too does not return expected value due to consumption of the CPU by the black hole. > (Actually, there is no variable in the predicate other than those > implied in sub-expressions of Earth turning a black hole. Your fault. Formally no such predicate could even exist, merely due to Goedel incompleteness. There is an old programmer's saying: never check bugs you are not going fix... -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de