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: 
 border1.nntp.ams3.giganews.com!border1.nntp.ams2.giganews.com!border3.nntp.ams.giganews.com!nntp.giganews.com!news.osn.de!diablo2.news.osn.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Possible for Ada 2020: "Cursors" for Arrays
Date: Tue, 04 Jun 2013 08:19:00 +0200
Organization: Tidorum Ltd
Message-ID: <b15f6kFrfs6U1@mid.individual.net>
References: <55016aa4-4d69-4fd9-a2c9-a7eb7d3b00c5@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Trace: individual.net 2dmh6bGoMViNzEzU5MFgTw++n/x0O+TcJsKh83BGdRlkvncMSm
Cancel-Lock: sha1:AvNP/1g7Oq2PKdV25c85E6WADTo=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6;
 rv:17.0) Gecko/20130509 Thunderbird/17.0.6
In-Reply-To: <55016aa4-4d69-4fd9-a2c9-a7eb7d3b00c5@googlegroups.com>
X-Original-Bytes: 2278
Xref: number.nntp.dca.giganews.com comp.lang.ada:181793
Date: 2013-06-04T08:19:00+02:00
List-Id: <comp.lang.ada>

On 13-06-04 03:09 , Shark8 wrote:
> In a few threads a few people have expressed a desire
> to be able to initialize Arrays based on some formula
> usually including the indices. In order to do this we
> need some sort of "cursor"-type/attribute.

Maybe...

> So, let us propose a cursor-attribute so that some array
> type, T1, defined as
>   type T1 is Array( 1..10 ) of Integer;
> could have a variable initialized as follows:
>   V1 : T1:= (others => T1'Cursor'Index)
> resulting in V1 getting (1,2,3,4,5,6,7,8,9,10);

I think it would be better to build this ability from syntax similar to
the quantified expressions - "for all/some I in <range> => ...". To
avoid ambiguities when the array elements are Boolean we should use a
new keyword instead of "all" or "some". I would also not put this after
"others", but directly as an "array_component_association":

   V1 : T1 := (for each I in T1'Range => I);

But this would make yet another useful word ("each") reserved... Perhaps
we can do without any keyword:

   V1 : T1 := (for I in T1'Range => I);

> My question: does this look reasonable, or is it
> just superfluous?

Superfluous, yes, perhaps with the exception of some corner cases such
as initializing large systematic arrays during pre-elaboration. But nice
to have, why not.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .