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From: "E. Robert Tisdale" <edwin@netwood.net>
Subject: Re: Conditional Compilation
Date: 2000/09/19
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Newsgroups: comp.lang.ada
Date: 2000-09-19T00:00:00+00:00
List-Id: <comp.lang.ada>

Kenneth Kueny wrote:

> Does ADA have an analog to the C language #define, #ifdef constructs
> commonly used to include or exclude certain blocks of code
> in different code versions?

This is a bit confusing.
The C macro preprocessor wasn't originally part
of the C computer programming language.
It was, and still is, a separate program
which accepted a C program "source file"
and emitted a C program "translation unit".
The typical C compiler accepts a translation unit
and compiles it into assembly language code
then calls the assembler to generate machine code.
The ANSI/ISO C/C++ standards now specify
syntax and semantics for the C macro preprocessor
but you can still use the C macro preprocessor
on Ada source files as long as the translation unit
is an acceptable Ada program.
Try it.  It works.

Now, professional programmers almost never write
programs in Ada, C, C++ or any other standard
computer programming language directly.
They usually use perl, the m4 macro preprocessor,
the sed stream editor or some combination of tools
to write programs for them from "prototype files"
which they maintain instead of source files.
Of course, if you are distributing "open source" programs,
you will need to distribute the prototype files
and any special tools along with the source files
so that other programmers can help to maintain
an contribute to the prototype files as well.