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<td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Preface</font></b></font></td>
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<p>During the last time many new features were developed as additions to the <tt>Spirit</tt>
<a href="references.html#spirit">[4]</a> parser construction framework and we
felt more and more, that it would be very helpful, to have a 'real world' example,
which could be used as a sandbox for testing the usability of certain features.
Additionally a recent discussion on the Boost mailing list showed the widespread
interest of developers to have a modern, open source C++ preprocessor library
to play with. So we had the idea to implement a C++ preprocessor to fit
this needs - <tt>Wave</tt> was born.</p>
<p align="justify">The <tt>Wave</tt> C++ preprocessor library uses the <a href="http://spirit.sourceforge.net/">
</a> <tt>Spirit<a href="references.html#spirit">[4]</a></tt> parser construction
library to implement a C++ lexer with ISO/ANSI standard conformant preprocessing
capabilities. It exposes an iterator interface, which returns the current preprocessed
token from the input stream. This preprocessed token is generated on the fly
while iterating over the preprocessor iterator sequence (in the terminology
of the STL these iterators are forward iterators). </p>
<p align="justify"> The C++ preprocessor is a macro processor that under normal
circumstances is used automatically by your C++ compiler to transform your program
before actual compilation. It is called a macro processor because it allows
you to define macros, which are brief abbreviations for longer constructs. The
C++ preprocessor provides four separate facilities that you can use as you see
fit: </p>
<blockquote>
<p><b><img src="theme/bullet.gif" width="13" height="13" id="IMG1"> </b>Inclusion
of header files<br>
<b><img src="theme/bullet.gif" width="13" height="13" id="IMG1"> </b>Macro
expansion<br>
<b><img src="theme/bullet.gif" width="13" height="13" id="IMG1"> </b>Conditional
compilation<br>
<b><img src="theme/bullet.gif" width="13" height="13" id="IMG1"> </b>Line
control</p>
</blockquote>
<p>These features are greatly underestimated today, even more, the preprocessor
has been frowned on for so long that its usage just hasn't been effectively
pushed until the Boost preprocessor library <a href="references.html#pp_lib">[7]</a>
came into being a few years ago. Only today we begin to understand, that preprocessor
generative metaprogramming combined with template metaprogramming in C++ is
by far one of the most powerful compile-time reflection/metaprogramming facilities
that any language has ever supported.</p>
<p align="justify">The main goals for the <tt>Wave</tt> project are:</p>
<blockquote>
<p><b><img src="theme/bullet.gif" width="13" height="13" id="IMG1"> </b>full
conformance with the C++ standard (ISO/IEC 14882:1998) <a href="references.html#iso_cpp">[1]</a>
and with the C99 standard (INCITS/ISO/IEC 9899:1999) <a href="references.html#iso_c">[2]</a><br>
<b><img src="theme/bullet.gif" width="13" height="13"> </b>usage of <tt>Spirit<a href="references.html#spirit">[4]</a></tt>
for the parsing parts of the game (certainly :-)<br>
<b><img src="theme/bullet.gif" width="13" height="13"> </b>maximal usage
of STL and/or <tt>Boost</tt> libraries (for compactness and maintainability)<br>
<b><img src="theme/bullet.gif" width="13" height="13"> </b>straightforward
extendability for the implementation of additional features<br>
<b><img src="theme/bullet.gif" width="13" height="13"> </b>building a
flexible library for different C++ lexing and preprocessing needs</p>
</blockquote>
<p>At the first steps it is not planned to make a very high performance or very
small C++ preprocessor. If you are looking for these objectives you probably
have to look at other places. Although our C++ preprocessor iterator should
work as expected and will be usable as a reference implementation, for instance
for testing of other preprocessor oriented libraries as the Boost Preprocessor
library <a href="references.html#pp_lib">[7]</a> et.al.</p>
<p>As tests showed, the <tt>Wave</tt> library is very conformant to the C++ Standard,
such that it compiles several strict conformant macro definitions, which are
not even compilable with EDG based preprocessors (i.e. Comeau or Intel). It
is shown further, that the EDG preprocessor will outperform the <tt>Wave</tt>
preprocessor in simple cases. However, as complexity increases, time dilates
expontentially on EDG. Preprocessing time dilates linearly under <tt>Wave</tt>,
which causes it to easily outperform EDG based preprocessors when complexity
increases.</p>
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<p class="copyright">Copyright © 2003-2004 Hartmut Kaiser<br>
<br>
<font size="2">Use, modification and distribution is subject to the Boost Software
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
</font> </p>
<span class="updated">Last updated:
<!-- #BeginDate format:fcAm1m -->Monday, January 5, 2004 14:57<!-- #EndDate -->
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