Re: Text control characters

[Stephen Leake <Stephen.Leake@gsfc.nasa.gov>]

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