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!feeder.eternal-september.org!gandalf.srv.welterde.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED.rrsoftware.com!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: class wide iterable (and indexable)
Date: Tue, 22 Jan 2019 16:02:32 -0600
Organization: JSA Research & Innovation
Message-ID: <q283tp$6tj$1@franka.jacob-sparre.dk>
References: <b5c56fdb-94d0-4930-952c-7754ec5dd729@googlegroups.com>
 <lyo98z558g.fsf@pushface.org>
 <2a6929c5-72fa-4d84-953a-44ea4597ab38@googlegroups.com>
 <q0m3u6$t9c$1@franka.jacob-sparre.dk>
 <f62bb15c-ebd2-45f7-b591-796a1957e99a@googlegroups.com>
 <q0n6av$1tqs$1@gioia.aioe.org> <q0psvi$v1q$1@franka.jacob-sparre.dk>
 <q0pvlp$1vp1$1@gioia.aioe.org> <q10f1v$v9r$1@franka.jacob-sparre.dk>
 <q11rqe$dtn$1@gioia.aioe.org> <q13biq$nle$1@franka.jacob-sparre.dk>
 <q159mg$1q6k$1@gioia.aioe.org> <q160mb$863$1@franka.jacob-sparre.dk>
 <q1715k$1fou$1@gioia.aioe.org> <q18g50$86r$1@franka.jacob-sparre.dk>
 <q19mh2$19lu$1@gioia.aioe.org> <q1j489$oo8$1@franka.jacob-sparre.dk>
 <q1k9ep$aku$1@gioia.aioe.org>
 <75328dc5-fc59-4228-b77e-77ba6e5101c3@googlegroups.com>
 <q25jpn$jfu$1@franka.jacob-sparre.dk> <q27if9$b0r$1@dont-email.me>
Injection-Date: Tue, 22 Jan 2019 22:02:33 -0000 (UTC)
Injection-Info: franka.jacob-sparre.dk;
 posting-host="rrsoftware.com:24.196.82.226";
	logging-data="7091"; mail-complaints-to="news@jacob-sparre.dk"
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Response
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.7246
Xref: reader01.eternal-september.org comp.lang.ada:55328
Date: 2019-01-22T16:02:32-06:00
List-Id: <comp.lang.ada>

"Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org> wrote in message 
news:q27if9$b0r$1@dont-email.me...
> On 1/22/19 12:15 AM, Randy Brukardt wrote:
>>
>> Moreover, in a new Ada-like language, it would make the most sense to
>> completely unify containers and arrays, which would mean that arrays 
>> would
>> be more like Vectors than like Ada arrays. For instance, in a Vector, the
>> lower bound is fixed for all values of a particular type. That would
>> eliminate a lot of programming errors that happen in Ada programs (many
>> programs fail to deal with unusual lower bounds, because it's hard to get
>> right).
>
> Ada has always had the ability to define array-like types with a fixed 
> lower bound:
>
> type String_From_1 (Length : Natural) is record
>    Value : String (1 .. Length);
> end record;
>
> I use such constructs when appropriate (in mathematics, for example, 
> matrices and vectors have indices with lower values of 1, and a decent 
> implementation should reflect and enforce that). One might argue that the 
> reason they're not used more often is because of the value of having array 
> types with variable lower bounds, but I doubt it.

They're not used more often because this fixes the length, and prevents 
operations on items with different lengths. Again, a string is not an 
array -- a Vector is a better model for a string.

                               Randy.