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!nntp-feed.chiark.greenend.org.uk!ewrotcd!reality.xs3.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012 Constraints (WRT an Ada IR)
Date: Mon, 19 Dec 2016 16:57:30 -0600
Organization: JSA Research & Innovation
Message-ID: <o39okq$lqe$1@franka.jacob-sparre.dk>
References: <c06ee4e6-d616-4e01-ba2e-cb111a81f6f6@googlegroups.com>
 <o2js2d$1qh4$1@gioia.aioe.org> <o2ke6d$gcs$1@dont-email.me>
 <o2ln13$et0$1@gioia.aioe.org> <o2mfpc$ttp$1@dont-email.me>
 <o2mncc$gjn$1@gioia.aioe.org> <o2mroh$dsk$1@dont-email.me>
 <o2n2o1$1515$1@gioia.aioe.org> <o2o73n$ci1$1@dont-email.me>
 <o2obed$qkk$1@gioia.aioe.org> <o2oj2u$i8h$1@dont-email.me>
 <o2olfi$1ca9$1@gioia.aioe.org> <o2p9bb$bcf$1@dont-email.me>
 <o2po6a$1hnq$1@gioia.aioe.org>
 <999c67b0-4478-4d2b-8108-32ac48fe6316@googlegroups.com>
 <o2r0lo$175u$1@gioia.aioe.org>
 <a960c6dd-80aa-4c9f-bf3b-47da529e0e01@googlegroups.com>
 <o2s8l1$1fef$1@gioia.aioe.org>
 <f1cebe17-25b1-4f75-9c1d-ff89d869aa87@googlegroups.com>
 <o2tl0b$1af0$1@gioia.aioe.org> <o2trb6$aso$1@dont-email.me>
 <o2u54i$73i$1@gioia.aioe.org> <o2us43$gik$1@dont-email.me>
 <o30e6s$1oqo$1@gioia.aioe.org> <o30k7g$cif$1@dont-email.me>
 <alpine.DEB.2.20.1612161308590.29766@debian> <o31j3h$so5$1@dont-email.me>
 <alpine.DEB.2.20.1612171023380.1039@debian>
NNTP-Posting-Host: rrsoftware.com
X-Trace: franka.jacob-sparre.dk 1482188250 22350 24.196.82.226 (19 Dec 2016
 22:57:30 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Mon, 19 Dec 2016 22:57:30 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
X-RFC2646: Format=Flowed; Original
Xref: news.eternal-september.org comp.lang.ada:32916
Date: 2016-12-19T16:57:30-06:00
List-Id: <comp.lang.ada>

<Stefan.Lucks@uni-weimar.de> wrote in message 
news:alpine.DEB.2.20.1612171023380.1039@debian...
...
>The else-clause still turns the Pre aspect into a postcondition.
>
>On the other hand, Randy's point is quite convincing: If we want to
>introduce contracts -- and, specifically, preconditions -- into existing
>libraries without breaking compatibility, then the else clause is exactly
>what is needed.

I know the point is convincing; we spent significant parts of ARG meetings 
in 2012 inventing the raise expression (and lots of other rejected solutions 
to this problem) specifically because I had convinced the rest of the ARG 
that this needed  to be addressed. :-) I'd be surprised if it has lost its 
power in the intervening years.

                                     Randy.