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    <td width="85%" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Regular Expression Parser</b></font></td>
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<p><a name="regular_expression_parser"></a>Regular expressions are a form of pattern-matching 
  that are often used in text processing. Many users will be familiar with the 
  usage of regular expressions. Initially there were the Unix utilities grep, 
  sed and awk, and the programming language perl, each of which make extensive 
  use of regular expressions. Today the usage of such regular expressions is integrated 
  in many more available systems.</p>
<p>During parser construction it is often useful to have the power of regular 
  expressions available. The Regular Expression Parser was introduced, to make 
  the use of regular expressions accessible for Spirit parser construction.</p>
<p>The Regular Expression Parser <tt>rxstrlit</tt> has a single template type 
  parameter: an iterator type. Internally, <tt>rxstrlit</tt> holds the Boost Regex 
  object containing the provided regular expression. The <tt>rxstrlit</tt> attempts 
  to match the current input stream with this regular expression. The template 
  type parameter defaults to <tt>char const<span class="operators">*</span></tt>. 
  <tt>rxstrlit</tt> has two constructors. The first accepts a null-terminated 
  character pointer. This constructor may be used to build <tt>rxstrlit's</tt> 
  from quoted regular expression literals. The second constructor takes in a first/last 
  iterator pair. The function generator version is <tt>regex_p</tt>. </p>
<p>Here are some examples:</p>
<pre><code><span class=comment>    </span><span class=identifier>rxstrlit</span><span class=special>&lt;&gt;(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>)
    </span><span class=identifier>regex_p</span><span class=special>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>)

    </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>);
    rx</span><span class=identifier>strlit</span><span class=special>&lt;&gt;(</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>
<p>The generated parser object acts at the character level, thus an eventually 
  given skip parser is not used during the attempt to match the regular expression 
  (see <a href="faq.html#scanner_business">The Scanner Business</a>).</p>
<p>The Regular Expression Parser is implemented by the help of the <a href="http://www.boost.org/libs/regex/index.html">Boost 
  Regex++ library</a>, so you have to have some limitations in mind. </p>
<blockquote>
  <p><img src="theme/bullet.gif" width="12" height="12"> Boost libraries have 
    to be installed on your computer and the Boost root directory has to be added 
    to your compiler <tt>#include&lt;...&gt;</tt> search path. You can download 
    the actual version at the <a href="http://www.boost.org/">Boost web site</a>.</p>
  <p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library 
    requires the usage of bi-directional iterators. So you have to ensure this 
    during the usage of the Spirit parser, which contains a Regular Expression 
    Parser.</p>
  <p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library 
    is not a header only library, as Spirit is, though it provides the possibility 
    to include all of the sources, if you are using it in one compilation unit 
    only. Define the preprocessor constant <tt>BOOST_SPIRIT_NO_REGEX_LIB</tt> before 
    including the spirit Regular Expression Parser header, if you want to include 
    all the Boost Regex sources into this compilation unit. If you are using the 
    Regular Expression Parser in more than one compilation unit, you should not 
    define this constant and must link your application against the regex library 
    as described in the related documentation.</p>
</blockquote>
<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>
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<p class="copyright">Copyright &copy; 2001-2002 Hartmut Kaiser<br>
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  <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>
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