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!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Bob Duff <bobduff@theworld.com>
Newsgroups: comp.lang.ada
Subject: Re: function Is_Open (File : File_Type) return Boolean; :Text_io
Date: Mon, 26 Oct 2015 18:48:51 -0400
Organization: A noiseless patient Spider
Message-ID: <87twpd2qlo.fsf@theworld.com>
References: <f30bbb5d-ebfd-427b-8c16-88aeb8a61318@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: mx02.eternal-september.org;
 posting-host="ff390eae7dae78eb85daece3eef8a589";
	logging-data="30204"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX1+xA0r5D3zKZ+LFPbJIDeAy"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)
Cancel-Lock: sha1:JfF4lg6r9W/5Mea9TOued9rNcHY=
	sha1:6GGSIWol3azvEj/4YY7Ax3X9iKE=
Xref: news.eternal-september.org comp.lang.ada:28064
Date: 2015-10-26T18:48:51-04:00
List-Id: <comp.lang.ada>

comicfanzine@gmail.com writes:

> Can someone please show my a code in which this function is used , i'm
> lost , thanks .

Most code is written so that it is statically known whether a file is
open, so Is_Open is close to useless.  Not entirely useless -- you might
use it in an assertion, such as:

    subtype Open_File is File with Predicate => Is_Open(Open_File);

And Niklas Holsti gave a fairly realistic example where it is NOT
statically known whether the file is open, so the program checks at run
time.

- Bob