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-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,3e5f85a85cdab16e,start
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2001-03-22 02:34:05 PST
Path: 
 supernews.google.com!sn-xit-03!supernews.com!freenix!fr.clara.net!heighliner.fr.clara.net!newsfeed01.sul.t-online.de!t-online.de!news.csl-gmbh.net!news1.dtag.de!newsserv.vs.dasa.de!news
From: "Oliver Kellogg" <oliver.kellogg@vs.dasa.de>
Newsgroups: comp.lang.ada
Subject: Should this be legal?
Date: Thu, 22 Mar 2001 11:13:16 +0100
Organization: Daimler-Benz Aerospace
Message-ID: <99cjt2$v9g@newsserv.vs.dasa.de>
NNTP-Posting-Host: kellol.vs.dasa.de
X-Newsreader: Microsoft Outlook Express 4.72.3155.0
X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3155.0
Xref: supernews.google.com comp.lang.ada:5988
Date: 2001-03-22T11:13:16+01:00
List-Id: <comp.lang.ada>

Hello Ada experts,

The full declaration of the Derived type looks different than
the partial view (Base_2 vs. Base(2))

Should this be legal?
Rational Apex 3.2.0b and GNAT 3.13p both accept it.
(However, both compilers tend to have problems with this
type of construction - especially in more complicated contexts.)

But then, if Base_2 and Base(2) are supposedly interchangeable,
how come the function Legal is accepted but function Illegal is
refused ("constraint not allowed here") ?

Thanks,

Oliver M. Kellogg


-- subtyped_discriminant.ads

package Subtyped_Discriminant is

   type Base (N : Integer) is tagged null record;

   subtype Base_2 is Base (2);

   type Derived is new Base_2 with private;

private

   type Derived is new Base (2) with null record;

   -- However,

   function Legal return Base_2;

   function Illegal return Base (2);

end Subtyped_Discriminant;