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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>rxstr_p</tt>. </p>
<p>Here are some examples:</p>
<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>)
rx</span><span class=identifier>str_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><>(</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="scanner.html#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.htm">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<...></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>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>
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<p class="copyright">Copyright © 2001-2002 Hartmut Kaiser<br>
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