1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<html> 3<head> 4<title>Regular Expression Parser</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> 10<table width="100%" border="0" background="theme/bkd2.gif" cellspacing="2"> 11 <tr> 12 <td width="10" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b> </b></font></td> 13 <td width="85%" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Regular Expression Parser</b></font></td> 14 <td width="112" height="49"><a href="http://spirit.sf.net"><img src="theme/spirit.gif" width="112" height="48" align="right" border="0"></a></td> 15 </tr> 16</table> 17<br> 18<table border="0"> 19 <tr> 20 <td width="10"></td> 21 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 22 <td width="30"><a href="refactoring.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td> 23 <td width="30"><a href="scoped_lock.html"><img src="theme/r_arr.gif" border="0"></a></td> 24 </tr> 25</table> 26<p><a name="regular_expression_parser"></a>Regular expressions are a form of pattern-matching 27 that are often used in text processing. Many users will be familiar with the 28 usage of regular expressions. Initially there were the Unix utilities grep, 29 sed and awk, and the programming language perl, each of which make extensive 30 use of regular expressions. Today the usage of such regular expressions is integrated 31 in many more available systems.</p> 32<p>During parser construction it is often useful to have the power of regular 33 expressions available. The Regular Expression Parser was introduced, to make 34 the use of regular expressions accessible for Spirit parser construction.</p> 35<p>The Regular Expression Parser <tt>rxstrlit</tt> has a single template type 36 parameter: an iterator type. Internally, <tt>rxstrlit</tt> holds the Boost Regex 37 object containing the provided regular expression. The <tt>rxstrlit</tt> attempts 38 to match the current input stream with this regular expression. The template 39 type parameter defaults to <tt>char const<span class="operators">*</span></tt>. 40 <tt>rxstrlit</tt> has two constructors. The first accepts a null-terminated 41 character pointer. This constructor may be used to build <tt>rxstrlit's</tt> 42 from quoted regular expression literals. The second constructor takes in a first/last 43 iterator pair. The function generator version is <tt>regex_p</tt>. </p> 44<p>Here are some examples:</p> 45<pre><code><span class=comment> </span><span class=identifier>rxstrlit</span><span class=special><>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>) 46 </span><span class=identifier>regex_p</span><span class=special>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>) 47 48 </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>); 49 rx</span><span class=identifier>strlit</span><span class=special><>(</span><span class=identifier>msg</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(), </span><span class=identifier>msg</span><span class=special>.</span><span class=identifier>end</span><span class=special>());</span></code></pre> 50<p>The generated parser object acts at the character level, thus an eventually 51 given skip parser is not used during the attempt to match the regular expression 52 (see <a href="faq.html#scanner_business">The Scanner Business</a>).</p> 53<p>The Regular Expression Parser is implemented by the help of the <a href="http://www.boost.org/libs/regex/index.html">Boost 54 Regex++ library</a>, so you have to have some limitations in mind. </p> 55<blockquote> 56 <p><img src="theme/bullet.gif" width="12" height="12"> Boost libraries have 57 to be installed on your computer and the Boost root directory has to be added 58 to your compiler <tt>#include<...></tt> search path. You can download 59 the actual version at the <a href="http://www.boost.org/">Boost web site</a>.</p> 60 <p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library 61 requires the usage of bi-directional iterators. So you have to ensure this 62 during the usage of the Spirit parser, which contains a Regular Expression 63 Parser.</p> 64 <p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library 65 is not a header only library, as Spirit is, though it provides the possibility 66 to include all of the sources, if you are using it in one compilation unit 67 only. Define the preprocessor constant <tt>BOOST_SPIRIT_NO_REGEX_LIB</tt> before 68 including the spirit Regular Expression Parser header, if you want to include 69 all the Boost Regex sources into this compilation unit. If you are using the 70 Regular Expression Parser in more than one compilation unit, you should not 71 define this constant and must link your application against the regex library 72 as described in the related documentation.</p> 73</blockquote> 74<p> <img src="theme/lens.gif" width="15" height="16"> See <a href="../example/fundamental/regular_expression.cpp">regular_expression.cpp</a> for a compilable example. This is part of the Spirit distribution.</p> 75<table border="0"> 76 <tr> 77 <td width="10"></td> 78 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 79 <td width="30"><a href="refactoring.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td> 80 <td width="30"><a href="scoped_lock.html"><img src="theme/r_arr.gif" border="0"></a></td> 81 </tr> 82</table> 83<br> 84<hr size="1"> 85<p class="copyright">Copyright © 2001-2002 Hartmut Kaiser<br> 86 <br> 87 <font size="2">Use, modification and distribution is subject to the Boost Software 88 License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at 89 http://www.boost.org/LICENSE_1_0.txt)</font></p> 90</body> 91</html> 92
