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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Text control characters
Date: 1997/09/12
Message-ID: <EGEorv.GKs@world.std.com>#1/1
X-Deja-AN: 271982585
References: <uden6xytd8.fsf@tanana.llnl.gov>
 <5v9vj1$dge$1@goanna.cs.rmit.edu.au> <341954D6.162C@gsfc.nasa.gov>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-09-12T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <341954D6.162C@gsfc.nasa.gov>,
Stephen Leake  <Stephen.Leake@gsfc.nasa.gov> wrote:
>Dale Stanbrough wrote:
>> 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;

True, but it doesn't answer Dale's question: Is there any great harm?

>... 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:

Quite true, but what does moving the OS-dependent stuff into the body
have to do with the issue of whether one uses preprocessors or CM
systems to select pieces of code?  I mean, your technique of selecting a
particular file would work fine on specs, too.

In fact, it might be important for whatever-it-is to be in the spec.
E.g. suppose I want to declare an integer constant whose value is
OS-dependent, but I desperately want the constant to be static?

>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");
>--------------------

Then you need some way of selecting configuration files.  You can move
this problem around, and solve it with different tools, but you can't
make it go away!

- Bob