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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: GNAT's Text_IO & empty files
Date: 1998/07/07
Message-ID: <EACHUS.98Jul7165436@spectre.mitre.org>#1/1
X-Deja-AN: 369341596
References: <35A0B7C5.1011D794@Maths.UniNe.CH> <dewar.899765885@merv>
 <35A200D9.E5AAC021@maths.unine.ch>
Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.ada
Date: 1998-07-07T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <35A200D9.E5AAC021@maths.unine.ch> Gautier <gautier.demontmollin@maths.unine.ch> writes:

 > Maybe you mean that the line feed is a line and file terminator .  It's true
 > on Unix, it false on DOS or Windows, where it is a line separator.
 > It's like the ';' which follows intructions in Ada but separate them
 > in Pascal.

 > << These lines were not put in for amusement! >>

 > Oh, you surprise me! Are you serious?

   It is possible to have a mapping in Text_IO such that an empty file
contains no bytes.  However, to do that correctly requires relying on
state in the (Ada) file descriptor, since the Ada notion of a text
file ends with an line terminator, followed by a page terminator,
followed by the end of file.  Try it.  Open an empty file for reading,
and call Page.  It will return 1.  Now call End_of_File.  It will
return true.  Now call Skip_Line (or Skip_Page). Page is now 2, but
End_of_File is still true.  Call Skip_Line again and get End_Error.
--

					Robert I. Eachus

with Standard_Disclaimer;
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function Message (Text: in Clever_Ideas) return Better_Ideas is...