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=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,fc52c633190162e0
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news2.google.com!proxad.net!usenet-fr.net!gegeweb.org!news.ecp.fr!news.jacob-sparre.dk!pnx.dk!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Erasing inappropriate operations (was: why learn C?)
Date: Tue, 3 Apr 2007 18:44:55 -0500
Organization: Jacob's private Usenet server
Message-ID: <euuoqr$sr8$1@jacob-sparre.dk>
References: <1172144043.746296.44680@m58g2000cwm.googlegroups.com>
   <slrnetr31o.875.Marc.Boyer@localhost.localdomain>
   <1172161751.573558.24140@h3g2000cwc.googlegroups.com>
   <slrnetri6j.875.Marc.Boyer@localhost.localdomain>
   <546qkhF1tr7dtU1@mid.individual.net>
   <slrnett8ph.807.Marc.Boyer@localhost.localdomain>
   <5ZULh.48$YL5.40@newssvr29.news.prodigy.net>
   <1175215906.645110.217810@e65g2000hsc.googlegroups.com>
   <rOudnecT2dxOEZHbnZ2dnUVZ_qupnZ2d@comcast.com>
   <1175230700.925143.28490@n59g2000hsh.googlegroups.com>
   <slrnf0pfuv.qs.lutz@belenus.iks-jena.de>
   <1btkgzzj6zimp.acsq8mkzqz1w$.dlg@40tude.net>
   <1175488143.324741.283480@y80g2000hsf.googlegroups.com>
   <1lxqyx4ognsed$.ait5qqwujfo8$.dlg@40tude.net>
   <1175501959.751535.23190@d57g2000hsg.googlegroups.com>
   <eus40i$k0$1@jacob-sparre.dk>
 <1175604129.583861.40720@q75g2000hsh.googlegroups.com>
NNTP-Posting-Host: static-69-95-181-76.mad.choiceone.net
X-Trace: jacob-sparre.dk 1175643803 29544 69.95.181.76 (3 Apr 2007 23:43:23
 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Tue, 3 Apr 2007 23:43:23 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2800.1807
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1807
Xref: g2news1.google.com comp.lang.ada:14773
Date: 2007-04-03T18:44:55-05:00
List-Id: <comp.lang.ada>

"Ludovic Brenta" <ludovic@ludovic-brenta.org> wrote in message
news:1175604129.583861.40720@q75g2000hsh.googlegroups.com...
> Randy Brukardt:
> > the Amendment fixed the most important problem in Ada 95:
> > the inability to "erase" an inappropriate operation from a unit type
> > package.
>
> Could you please explain what you mean by this? A quick perusal of the
> Ada 2005 rationale failed to enlighten me.

In Ada 95, abstract operators of untagged types are considered in
resolution. So, you still might call them;then get an error message. That is
especially problematical if an appropriate operator is defined somewhere
else, because the expression might be ambiguous. (It's also a problem with
literals).

The Amendment 1 changed that so that they do not participate in resolution.
Thus, they no longer clog up resolution.

For instance, if you had:

     type F1 is digits 3;
     type F2 is digits 3;
     function "*" (Left : F1, Right : F2) return F2;
     function "*" (Left, Right : F2) return F2 is abstract; -- Don't want
this operator.

     A : F1 := 1.0;
     B : F2 := A * 1.0; -- (1)

The expression (1) is ambiguous in Ada 95 (even though one of the possible
operators is illegal). But Amendment 1 makes it OK; you'll get the intended
operator without interference from the predefined ones you don't want.

                                 Randy.