From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-0.9 required=3.0 tests=AC_FROM_MANY_DOTS,BAYES_00
	autolearn=no autolearn_force=no version=3.4.6
Path: eternal-september.org!reader02.eternal-september.org!news.gegeweb.eu!gegeweb.org!usenet-fr.net!proxad.net!feeder1-2.proxad.net!cleanfeed2-a.proxad.net!nnrp2-1.free.fr!not-for-mail
From: Thomas <fantome.forums.tDeContes@free.fr.invalid>
Newsgroups: comp.lang.ada
Mail-Copies-To: nobody
Subject: Re: array from static predicate on enumerated type
References: <89128f73-fcc5-4e57-8067-d09877ba0211n@googlegroups.com> <s2gqnf$vbs$1@gioia.aioe.org> <6ca041f3-2669-4497-9548-2f17666702a6n@googlegroups.com> <s2hrn2$3ee$1@gioia.aioe.org> <26c44e00-a899-455a-a929-1e23c7935fe3n@googlegroups.com> <9abb081d-a323-466d-9ae8-a2fc8fa24725n@googlegroups.com> <s2ofr1$1cg3$1@gioia.aioe.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
User-Agent: MT-NewsWatcher/3.5.3b3 (Intel Mac OS X)
Date: Wed, 16 Mar 2022 01:38:41 +0100
Message-ID: <fantome.forums.tDeContes-A2ED4E.01384016032022@news.free.fr>
Organization: Guest of ProXad - France
NNTP-Posting-Date: 16 Mar 2022 01:38:41 CET
NNTP-Posting-Host: 91.175.52.121
X-Trace: 1647391121 news-1.free.fr 29490 91.175.52.121:4334
X-Complaints-To: abuse@proxad.net
Xref: reader02.eternal-september.org comp.lang.ada:63608
List-Id: <comp.lang.ada>

In article <s2ofr1$1cg3$1@gioia.aioe.org>,
 "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote:

> On 2021-03-15 18:48, Shark8 wrote:
> 
> > So, in Ada, there's no good choice for how to actually DO an array with 
> > gaps in the index:
> 
> That applies to all containers. The problem is mapping the key to a 
> dense position when the key is not dense or might be unordered.
> 
> There is no gaps in positions.
> 
> > But Array *isn't* a map, though often it is substituted as one.
> 
> Of course it is, per definition of mapping. f : key -> element.
> 
> > Array has further constraints, like the contiguous memory labeled above.
> 
> No. The constraint here is a dense index. That is not specific to a 
> general map or an array. It is a fundamental property of the set of keys 
> being a convex set. Convex ensures certain useful mathematical 
> properties invariant to the representation of the mapping. In 
> particular, it gives a way to enumerate elements.

> Arbitrary predicate kills convex, so the problem. Not array. A map would 
> have just same problem: a map of LETTERS is in general not substitutable 
> for a map of CURVED_LETTERS.


i don't understand,
since Ada.Containers.Ordered_Maps.Key_Type is private,
and so new Ada.Containers.Ordered_Maps (CURVED_LETTERS, Integer) is 
allowed.

-- 
RAPID maintainer
http://savannah.nongnu.org/projects/rapid/