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<td width="21"> <h1></h1></td>
<td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Quick
Start </font></b></font></td>
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<p>Preprocessing with Wave is highly configurable. You must
define a few options to control it. Here are a few of the
options you can define:</p>
<BLOCKQUOTE dir="ltr" style="MARGIN-RIGHT: 0px">
<P><STRONG><IMG id="IMG1" height="13" src="theme/bullet.gif" width="13"></STRONG> include
search paths, 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>whether to enable any of several extensions to the C++
Standard (such as for variadics and placemarkers)<br>
</P>
</BLOCKQUOTE>
<p>You can access all these processing parameters through the <tt>boost::wave::context</tt>
object. So you must 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>boost::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 lexer iterator to be used as the token source for the preprocessing engine.</p>
<P dir="ltr">Do not instantiate the main preprocessing iterators yourself.
Get them from the wave::context object instead.<br>
The following code snippet is taken from the <tt>quick_start</tt> sample, which shows a minimal usage scenario for <tt>Wave</tt>. </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>);
<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 boost::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 some
// of the public classes and templates and it is returned
// from the iterators.
// The template boost::wave::cpplexer::lex_iterator<> is
// the lexer iterator to use as the token source for the
// preprocessing engine. In this case this is parametrized
// with the token type.</span>
<span class="keyword">typedef</span> <span class="identifier">boost::wave::cpplexer::lex_iterator</span><span class="special"><</span>
<span class="identifier">boost::wave::cpplexer::lex_token</span><span class="special"><> ></span>
<span class="identifier">lex_iterator_type</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">boost::wave::context</span><span class="special"><</span>
std::string::iterator<span class="special">,</span> lex_iterator_type<span class="special">></span>
<span class="identifier">context_type</span><span class="special">;</span>
context_type ctx(input.begin(), input.end(), <span class="string">"input.cpp"</span>);
<span class="comment"> // At this point you may want to set the parameters of the
// preprocessing as include paths and/or predefined macros.
</span> ctx.add_include_path(<span class="literal">"..."</span>);
ctx.add_macro_definition(...);
<span class="comment"> // Get the preprocessor iterators and use them to generate
// the token sequence.
</span> context_type::iterator_type first = ctx.begin();
context_type::iterator_type last = ctx.end();
<span class="comment"> // The input stream is preprocessed for you during iteration<br> // over [first, last)<br></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>boost::wave::context</tt> object can
take a pair of arbitrary iterator types (at least <tt>input_iterator</tt> type
iterators) to the input stream, which must supply the data to be processed.
The third parameter supplies a filename, filename, which is reported in the preprocessor output to
indicate the current context.
Note though, that this filename is used
only as long as no <tt>#include</tt> or <tt>#line</tt> directives are encountered,
which in turn will alter the current filename reported.</P>
<P dir="ltr">The iteration over the preprocessed tokens is relativley straightforward. Just get the starting and the ending iterators from the context object
(maybe after initializing some include search paths) and you are done! Dereferencing
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 © 2003-2005 Hartmut Kaiser<br>
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<font size="2">Distributed under 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"></span>
<p class="copyright"><span class="updated">Last updated:
<!-- #BeginDate format:fcAm1m -->Sunday, May 15, 2005 12:23<!-- #EndDate -->
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