From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=0.8 required=3.0 tests=BAYES_50,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.5-pre1
X-Received: by 2002:ac8:4705:: with SMTP id f5mr73342431qtp.37.1609844672063;
        Tue, 05 Jan 2021 03:04:32 -0800 (PST)
X-Received: by 2002:a25:6ec3:: with SMTP id j186mr114006792ybc.165.1609844671864;
 Tue, 05 Jan 2021 03:04:31 -0800 (PST)
Path: eternal-september.org!reader02.eternal-september.org!news.gegeweb.eu!gegeweb.org!usenet-fr.net!proxad.net!feeder1-2.proxad.net!209.85.160.216.MISMATCH!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Tue, 5 Jan 2021 03:04:31 -0800 (PST)
Complaints-To: groups-abuse@google.com
Injection-Info: google-groups.googlegroups.com; posting-host=20.133.0.13; posting-account=YRfoYAoAAADhSEO2nLYx10QUUvp8akYl
NNTP-Posting-Host: 20.133.0.13
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <1cc09f04-98f2-4ef3-ac84-9a9ca5aa3fd5n@googlegroups.com>
Subject: Lower bounds of Strings
From: Stephen Davies <joviangm@gmail.com>
Injection-Date: Tue, 05 Jan 2021 11:04:32 +0000
Content-Type: text/plain; charset="UTF-8"
Xref: reader02.eternal-september.org comp.lang.ada:61035
List-Id: <comp.lang.ada>


I'm sure this must have been discussed before, but the issue doesn't
seem to have been resolved and I think it makes Ada code look ugly and
frankly reflects poorly on the language.

I'm referring to the fact that any subprogram with a String
parameter, e.g. Expiration_Date, has to use something like
Expiration_Date (Expiration_Date'First .. Expiration_Date'First + 1)
to refer to the first two characters rather than simply saying
Expiration_Date (1..2).

Not only is it ugly, but it's potentially dangerous if code uses the
latter and works for ages until one day somebody passes a slice instead
of a string starting at 1 (yes, compilers might generate warnings,
but that doesn't negate the issue, imho).

There must be many possible solutions, without breaking compatibility
for those very rare occasions where code actually makes use of the
lower bound of a string.

e.g. Perhaps the following could be made legal and added to Standard:

subtype Mono_String is String (1 .. <>);

One question with this would be whether or not to allow procedure bodies
to specify parameters as Mono_String when the corresponding procedure
declaration uses String.