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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: {Pre,Post}conditions and side effects
Date: Wed, 13 May 2015 11:35:54 +0200
Organization: cbb software GmbH
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References: 
 <2430252d-52a1-4609-acef-684864e6ca0c@googlegroups.com><AnYlw.957256$Rp.242412@fx23.iad><0a718b39-ebd3-4ab5-912e-f1229679dacc@googlegroups.com><wccoaqucn51.fsf@shell01.TheWorld.com><9ee5e186-5aaa-4d07-9490-0f9fdbb5ca18@googlegroups.com><alpine.CYG.2.11.1412231747100.4196@WIL414CHAPIN.vtc.vsc.edu><wccegrpq2om.fsf@shell01.TheWorld.com><87tww5296f.fsf@adaheads.sparre-andersen.dk><871tj9dp5b.fsf@theworld.com><ce4af31e-d491-479f-a5b3-0b3eedea2a68@googlegroups.com><midvq5$2u3$1@loke.gir.dk><alpine.DEB.2.11.1505071103310.14859@debian><migc9a$jp8$1@loke.gir.dk><alpine.DEB.2.11.1505072052570.16448@debian><mijen0$1hj$1@loke.gir.dk>
 <87pp6a1u9w.fsf@jester.gateway.sonic.net><mirhjl$kvm$1@loke.gir.dk>
 <877fsd1xb5.fsf@jester.gateway.sonic.net> <mitt8a$goo$1@loke.gir.dk>
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Xref: news.eternal-september.org comp.lang.ada:25862
Date: 2015-05-13T11:35:54+02:00
List-Id: <comp.lang.ada>

On Tue, 12 May 2015 17:01:45 -0500, Randy Brukardt wrote:

> "Paul Rubin" <no.email@nospam.invalid> wrote in message 
> news:877fsd1xb5.fsf@jester.gateway.sonic.net...
>> "Randy Brukardt" <randy@rrsoftware.com> writes:
>>>> Randy, is that a real possibility with SPARK--to have a predicate that
>>>> says that an array is sorted
>>> I have no idea, SPARK is not at all my idea of how Ada should work.
>>
>> Hmm, ok, I had been confused on that issue.
>>
>> So can you say what the predicate for a sorted array would look like in
>> Janus/ADA, and how the compiler would verify it?
> 
> I answered that somewhere else in this thread (it just uses appropriate 
> predicates, usually "Dynamic_Predicates" since static predicates cannot 
> contain anything useful for composite types).

How so? Actually, the "sorted" predicate of an operation is rubbish. The
proper design is a composite type Sorted_Array with an *invariant* that
ensures the array sorted. The invariant must be static, of course, as
everything else regarding correctness.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de