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From: Stephen Leake <Stephen.Leake@gsfc.nasa.gov>
Subject: Re: Text control characters
Date: 1997/09/12
Message-ID: <341954D6.162C@gsfc.nasa.gov>#1/1
X-Deja-AN: 271896231
References: <uden6xytd8.fsf@tanana.llnl.gov>
 <5v9vj1$dge$1@goanna.cs.rmit.edu.au>
Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA
Reply-To: Stephen.Leake@gsfc.nasa.gov
Newsgroups: comp.lang.ada
Date: 1997-09-12T00:00:00+00:00
List-Id: <comp.lang.ada>


Dale Stanbrough wrote:
> 
> package Unix.Line_Terminators is
>    Line_Terminator : constant String := Ascii.LF & "";
> 
> end;
> 
> with Unix.Line_Terminators;
> package OS.Line_Terminators is
> 
>    Line_Terminator : String renames Unix.Line_Terminators.Line_Terminator;
> 
> end;
> 
> and then get your configuration system to choose the appropriate with
> (maybe even use a preprocessor! to select a with statement).
> 
> Thinking about it, the preprocessor selection of a with statement
> would seem to be a fairly benign use of preprocessors. Can anyone see
> any great harm in this scheme?

you don't need a preprocessor; you can set things up so only the BODY of
the package is OS dependent, and let the CM system choose which FILE to
use for the body:

file os-line_terminator.ads:
--------------------
package OS.Line_Terminators is
   function Line_Terminator return String;
end OS.Line_Terminators;
--------------------

file os-line_terminator__aix432.adb:
--------------------
package body OS.Line_Terminators is
   -- this is for AIX 4.3.2
   function Line_Terminator return String is
   begin
      return "" & Ascii.LF;
   end Line_terminator;
end OS.Line_Terminators;
--------------------

Under GNAT, since we're not using the conventional name for the body
file, we need a configuration pragma:

file gnat.adc:
--------------------
pragma Source_File_Name (OS.Line_Terminators,
                         BODY_FILE_NAME =>
"os-line_terminator__aix432.adb");
--------------------

other compilers will have other ways of specifying which file contains
which
compilation unit.

-- 
- Stephe