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!news.eternal-september.org!feeder.eternal-september.org!nntp-feed.chiark.greenend.org.uk!ewrotcd!reality.xs3.de!news.jacob-sparre.dk!loke.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: The future of Spark . Spark 2014 : a wreckage
Date: Wed, 17 Jul 2013 18:08:17 -0500
Organization: Jacob Sparre Andersen Research & Innovation
Message-ID: <ks7851$3mm$1@loke.gir.dk>
References: <1d4tuwlfdnz2j$.18l68s96x3vjj.dlg@40tude.net>
 <984821833395507830.672948rm-host.bauhaus-maps.arcor.de@news.arcor.de>
 <ks23dp$npd$1@loke.gir.dk>
 <e7de5753-5819-41a4-a40f-3d80c101bf03@googlegroups.com>
NNTP-Posting-Host: static-69-95-181-76.mad.choiceone.net
X-Trace: loke.gir.dk 1374102497 3798 69.95.181.76 (17 Jul 2013 23:08:17 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Wed, 17 Jul 2013 23:08:17 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Original
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
Xref: news.eternal-september.org comp.lang.ada:16398
Date: 2013-07-17T18:08:17-05:00
List-Id: <comp.lang.ada>

"Shark8" <onewingedshark@gmail.com> wrote in message 
news:e7de5753-5819-41a4-a40f-3d80c101bf03@googlegroups.com...
...
>The one drawback from your proposal is that it makes you reiterate the 
>condition,
>but with a negation, this could be a source of bugs. Even though it's a 
>little less
>straightforward the following would circumvent that problem:

> procedure Op (x : in out T)
>   with Post => (Constraint_Error at [not?] Foo(x));

I didn't mean this to be a real example. An example like the one given 
probably would have been better written as a precondition (depending on 
exactly what Foo does):

  procedure Op (x : in out T)
     with Pre => Foo(x) or else raise Constraint_Error,
            Post => Foo(x);

which is just normal Ada 2012 code (using the raise expression, which we 
added 'after the fact' to support this usage).

I don't think most exception contracts would have an associated 
postcondition (that is, cause); what would the postcondition be for 
Use_Error, for instance? It's just an optional help in a few circumstances.

                                                Randy.