1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<html> 3<head> 4<title>Quick Start</title> 5<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> 6<link href="theme/style.css" rel="stylesheet" type="text/css"> 7</head> 8 9<body text="#000000" background="theme/bkd.gif"> 10<table width="100%" border="0" cellspacing="2" background="theme/bkd2.gif"> 11 <tr> 12 <td width="21"> <h1></h1></td> 13 <td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Quick 14 Start </font></b></font></td> 15 <td width="96"><a href="http://www.boost.org"><img src="theme/wave.gif" width="93" height="68" align="right" border="0"></a></td> 16 </tr> 17</table> 18<br> 19<table border="0"> 20 <tr> 21 <td width="10"></td> 22 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 23 <td width="30"><a href="introduction.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td> 24 <td width="30"><a href="class_reference_context.html"><img src="theme/r_arr.gif" border="0"></a></td> 25 </tr> 26</table> 27<p>Preprocessing with <tt>Wave</tt> is highly configurable. You must 28define a few options to control it. Here are a few of the 29options you can define:</p> 30<BLOCKQUOTE dir="ltr" style="MARGIN-RIGHT: 0px"> 31 <P><STRONG><IMG id="IMG1" height="13" src="theme/bullet.gif" width="13"></STRONG> include 32 search paths defining where to search for files to be included with 33 <tt>#include <...></tt> and <tt>#include "..."</tt> directives<br> 34 <STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>which 35 macros to predefine and which of the predefined macros to undefine<br> 36 <STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>whether to enable any of several extensions to the C++ 37Standard (such as for variadics and placemarkers) 38 </P> 39</BLOCKQUOTE> 40<p>You can access all these processing parameters through the <tt>boost::wave::context</tt> 41 object. So you must instantiate one object instance of this type to use the <tt>Wave</tt> 42 library. (For more information about the context template class, please refer 43 to the class reference <a href="class_reference_context.html">here</a>.) To instantiate 44 the <tt>boost::wave::context</tt> object you have to supply at least two template parameters: 45 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> 46<P dir="ltr">Do not instantiate the main preprocessing iterators yourself. 47Get them from the <tt>boost::wave::context</tt> object instead. 48The following code snippet is taken from the <tt>quick_start</tt> sample, which shows a minimal usage scenario for <tt>Wave</tt>. </P> 49<pre><span class="comment"> // The following preprocesses a given input file. 50 // Open the file and read it into a string variable</span> 51 <span class="keyword">std::ifstream</span> instream(<span class="string">"input.cpp"</span>); 52 <span class="keyword">std::string </span>input<span class="keyword">( 53 std::istreambuf_iterator<char></span>(instream.rdbuf()), 54 <span class="keyword">std::istreambuf_iterator<char></span>()); 55 56 <span class="comment">// The template boost::wave::cpplexer::lex_token<> is the 57 // token type to be used by the Wave library. 58 // This token type is one of the central types throughout 59 // the library, because it is a template parameter to some 60 // of the public classes and templates and it is returned 61 // from the iterators. 62 // The template boost::wave::cpplexer::lex_iterator<> is 63 // the lexer iterator to use as the token source for the 64 // preprocessing engine. In this case this is parameterized 65 // with the token type.</span> 66 <span class="keyword">typedef</span> <span class="identifier">boost::wave::cpplexer::lex_iterator</span><span class="special"><</span> 67 <span class="identifier">boost::wave::cpplexer::lex_token</span><span class="special"><> ></span> 68 <span class="identifier">lex_iterator_type</span><span class="special">;</span> 69 <span class="keyword">typedef</span> <span class="identifier">boost::wave::context</span><span class="special"><</span> 70 std::string::iterator<span class="special">,</span> lex_iterator_type<span class="special">></span> 71 <span class="identifier">context_type</span><span class="special">;</span> 72 73 context_type ctx(input.begin(), input.end(), <span class="string">"input.cpp"</span>); 74<span class="comment"> 75 // At this point you may want to set the parameters of the 76 // preprocessing as include paths and/or predefined macros. 77</span> ctx.add_include_path(<span class="literal">"..."</span>); 78 ctx.add_macro_definition(...); 79<span class="comment"> 80 // Get the preprocessor iterators and use them to generate 81 // the token sequence. 82</span> context_type::iterator_type first = ctx.begin(); 83 context_type::iterator_type last = ctx.end(); 84 85<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) { 86 <span class="keyword">std::cout</span> << (*first).get_value(); 87 ++first; 88 } 89 90</pre> 91<P dir="ltr">The constructor of the <tt>boost::wave::context</tt> object can 92 take a pair of arbitrary iterator types (at least <tt>input_iterator</tt> type 93 iterators) to the input stream, which must supply the data to be processed. 94 The third parameter supplies a filename, which is reported in the preprocessor output to 95indicate the current context. 96Note though, that this filename is used 97 only as long as no <tt>#include</tt> or <tt>#line</tt> directives are encountered, 98 which in turn will alter the current reported filename.</P> 99<P dir="ltr">The iteration over the preprocessed tokens is relatively straightforward. Just get the starting and the ending iterators from the context object 100 (maybe after initializing some include search paths) and you are done! Dereferencing 101 the iterator will return the preprocessed tokens generated on 102 the fly from the input stream. (To get further information about the token type, 103 you may want to look <a href="class_reference_tokentype.html">here</a>.)</P> 104<table border="0"> 105 <tr> 106 <td width="10"></td> 107 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 108 <td width="30"><a href="introduction.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td> 109 <td width="30"><a href="class_reference_context.html"><img src="theme/r_arr.gif" border="0"></a></td> 110 </tr> 111</table> 112<hr size="1"> 113<p class="copyright">Copyright © 2003-2011 Hartmut Kaiser<br> 114 <br> 115<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> 116<span class="updated"></span> 117<p class="copyright"><span class="updated">Last updated: 118 <!-- #BeginDate format:fcAm1m -->Tuesday, July 29, 2008 20:34<!-- #EndDate --> 119</span></p> 120</body> 121</html> 122
