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From: Gautier.DeMontmollin@maths.unine.ch
Subject: Re: GNAT's Text_IO & empty files
Date: 1998/07/09
Message-ID: <m5IsbdWqXQh+@nedcu4>#1/1
X-Deja-AN: 369854937
References: <35A0B7C5.1011D794@Maths.UniNe.CH> <dewar.899765885@merv>
 <pdxk95ogpwl.fsf@vesuri.Helsinki.FI>
Organization: University of Neuchatel, Switzerland
Newsgroups: comp.lang.ada
Date: 1998-07-09T00:00:00+00:00
List-Id: <comp.lang.ada>

aaro@iki.fi (Aaro Koskinen) writes:

> Check the POSIX.2 definition of a text file. It says that lines
> terminate with LF, and a text file contains at least one line.

More and more interesting...

Is it so explicit in the Ada 95 definition of a text file ?

If no, there is a debate of whether we need compatibity between
different GNAT ports _or_ between a GNAT port and the programs
surrounding it.

The two notions are, in this case, partly incompatible...

To satisfy the 2nd, I suggest something like:

type t_text_file_style is (unix,dos);
text_file_style: t_text_file_style: constant boolean:= unix; 

The output will conform to text_file_style - not more than

         elsif text_file_style = unix
           and then (File /= Standard_Err and then File /= Standard_Out)
           and then (File.Line = 1 and then File.Page = 1)
         then
            New_Line (File);
         end if;

in Terminate_Line.
                                 
The input will be as tolerant as possible to satisfy the 1st
compatibility notion.

N.B.: I make abstraction of the fact that Unix'CR = DOS'CR/LF; this
is translated transparently now via networks or utilities or by lower level IO.

-- 
Gautier