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<td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Quick
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<p>The actual preprocessing itself is a highly configurable process, so obviously
you have to define a couple of parameters to control this process, such
as:</p>
<BLOCKQUOTE dir="ltr" style="MARGIN-RIGHT: 0px">
<P><STRONG><IMG id="IMG1" height="13" src="theme/bullet.gif" width="13"></STRONG> include
search pathes, which define, where to search for files to be included with
<tt>#include <...></tt> and <tt>#include "..."</tt> directives<br>
<STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>which
macros to predefine and which of the predefined macros to undefine<br>
<STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>several
other options as for instance to control, whether to enable several extensions
to the C++ Standard (as for instance variadics and placemarkers) or not.</P>
</BLOCKQUOTE>
<p>You can access all these processing parameters through the <tt>wave::context</tt>
object. So you have to instantiate one object of this type to use the <tt>Wave</tt>
library. For more information about the context template class please refer
to the class reference <a href="class_reference_context.html">here</a>. To instantiate
the <tt>wave::context</tt> object you have to supply at least two template parameters:
the iterator type of the underlying input stream to use and the type of the
token to be returned from the preprocessing engine.</p>
<P dir="ltr">The main preprocessing iterators are not to be instantiated directly,
but should be generated through this context object too. </P>
<pre><span class="comment"> // The following preprocesses a given input file.
// Open the file and read it into a string variable</span>
<span class="keyword">std::ifstream</span> instream(<span class="string">"input.cpp"</span>);<br> <span class="keyword">std::string </span>input<span class="keyword">(
std::istreambuf_iterator<char></span>(instream.rdbuf());
<span class="keyword">std::istreambuf_iterator<char></span>());
<span class="comment">// The template wave::cpplexer::lex_token<> is the token
// type to be used by the Wave library.
// This token type is one of the central types throughout
// the library, because it is a template parameter to many
// of the public classes and templates and it is returned
// from the iterators itself.</span>
<span class="keyword">typedef</span> wave::context<<span class=keyword>std::string::iterator</span>,
wave::cpplexer::lex_token<> >
context_t;
<span class="comment">// The C++ preprocessor iterators shouldn't be constructed
// directly. These are to be generated through a
// wave::context<> object. Additionally this wave::context<>
// object is to be used to initialize and define different
// parameters of the actual preprocessing.
</span> context_t ctx(input.begin(), input.end(), <span class="string">"input.cpp"</span>);
context_t::iterator_t first = ctx.begin();
context_t::iterator_t last = ctx.end();
<span class="comment"> // The preprocessing of the input stream is done on the fly
// behind the scenes during the iteration over the
// context_t::iterator_t based stream. </span>
<span class="keyword">while</span> (first != last) {
<span class="keyword">std::cout</span> << (*first).get_value();
++first;
}
</pre>
<P dir="ltr">The constructor of the <tt>wave::context<></tt> object can
take a pair of arbitrary iterator types (at least <tt>input_iterator</tt> type
iterators) to the input stream, from where should be read the data to be preprocessed.
The third parameter supplies a filename, which is used subsequently inside the
preprocessed tokens returned from the preprocessing to indicate the token position
inside the underlying input stream. Note though, that this filename is used
only as long no <tt>#include</tt> or <tt>#line</tt> directives are encountered,
which in turn will alter the current filename.</P>
<P dir="ltr">The iteration over the preprocessed tokens is relativly straight
forward. Just get the starting and the ending iterators from the context object
(maybe after initializing some include search paths) and you are done! The dereferencing
of the iterator will return the preprocessed tokens, which are generated on
the fly from the input stream. To get further information about the token type,
you may want to look <a href="class_reference_tokentype.html">here</a>.</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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