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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="string_algo.concept"></a>Concepts</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="concept.html#idp107053984">Definitions</a></span></dt>
<dt><span class="section"><a href="concept.html#string_algo.finder_concept">Finder Concept</a></span></dt>
<dt><span class="section"><a href="concept.html#string_algo.formatter_concept">Formatter concept</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="idp107053984"></a>Definitions</h3></div></div></div>
<div class="table">
<a name="idp107054624"></a><p class="title"><b>Table 2.13. Notation</b></p>
<div class="table-contents"><table class="table" summary="Notation">
<colgroup>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td align="left"><code class="computeroutput">F</code></td>
<td align="left">A type that is a model of Finder</td>
</tr>
<tr>
<td align="left"><code class="computeroutput">Fmt</code></td>
<td align="left">A type that is a model of Formatter</td>
</tr>
<tr>
<td align="left"><code class="computeroutput">Iter</code></td>
<td align="left">
Iterator Type
</td>
</tr>
<tr>
<td align="left"><code class="computeroutput">f</code></td>
<td align="left">Object of type <code class="computeroutput">F</code>
</td>
</tr>
<tr>
<td align="left"><code class="computeroutput">fmt</code></td>
<td align="left">Object of type <code class="computeroutput">Fmt</code>
</td>
</tr>
<tr>
<td align="left"><code class="computeroutput">i,j</code></td>
<td align="left">Objects of type <code class="computeroutput">Iter</code>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break">
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="string_algo.finder_concept"></a>Finder Concept</h3></div></div></div>
<p>
Finder is a functor which searches for an arbitrary part of a container.
The result of the search is given as an <code class="computeroutput">iterator_range</code>
delimiting the selected part.
</p>
<div class="table">
<a name="idp107070736"></a><p class="title"><b>Table 2.14. Valid Expressions</b></p>
<div class="table-contents"><table class="table" summary="Valid Expressions">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th align="left">Expression</th>
<th align="left">Return Type</th>
<th align="left">Effects</th>
</tr></thead>
<tbody><tr>
<td align="left"><code class="computeroutput">f(i,j)</code></td>
<td align="left">Convertible to <code class="computeroutput">iterator_range<Iter></code>
</td>
<td align="left">Perform the search on the interval [i,j) and returns the result of the search</td>
</tr></tbody>
</table></div>
</div>
<br class="table-break"><p>
Various algorithms need to perform a search in a container and a Finder is a generalization of such
search operations that allows algorithms to abstract from searching. For instance, generic replace
algorithms can replace any part of the input, and the Finder is used to select the desired one.
</p>
<p>
Note, that it is only required that the finder works with a particular iterator type. However,
a Finder operation can be defined as a template, allowing the Finder to work with any iterator.
</p>
<p>
<span class="bold"><strong>Examples</strong></span>
</p>
<p>
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
Finder implemented as a class. This Finder always returns the whole input as a match. <code class="computeroutput">operator()</code>
is templated, so that the finder can be used on any iterator type.
<pre class="programlisting">
struct simple_finder
{
template<typename ForwardIteratorT>
boost::iterator_range<ForwardIteratorT> operator()(
ForwardIteratorT Begin,
ForwardIteratorT End )
{
return boost::make_range( Begin, End );
}
};
</pre>
</li>
<li class="listitem">
Function Finder. Finder can be any function object. That is, any ordinary function with the
required signature can be used as well. However, such a function can be used only for
a specific iterator type.
<pre class="programlisting">
boost::iterator_range<std::string> simple_finder(
std::string::const_iterator Begin,
std::string::const_iterator End )
{
return boost::make_range( Begin, End );
}
</pre>
</li>
</ul></div>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="string_algo.formatter_concept"></a>Formatter concept</h3></div></div></div>
<p>
Formatters are used by <a class="link" href="design.html#string_algo.replace" title="Replace Algorithms">replace algorithms</a>.
They are used in close combination with finders.
A formatter is a functor, which takes a result from a Finder operation and transforms it in a specific way.
The operation of the formatter can use additional information provided by a specific finder,
for example <code class="computeroutput"><a class="link" href="../boost/algorithm/regex_formatter.html" title="Function template regex_formatter">regex_formatter()</a></code> uses the match information from
<code class="computeroutput"><a class="link" href="../boost/algorithm/regex_finder.html" title="Function template regex_finder">regex_finder()</a></code> to format the result of formatter operation.
</p>
<div class="table">
<a name="idp107091040"></a><p class="title"><b>Table 2.15. Valid Expressions</b></p>
<div class="table-contents"><table class="table" summary="Valid Expressions">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th align="left">Expression</th>
<th align="left">Return Type</th>
<th align="left">Effects</th>
</tr></thead>
<tbody><tr>
<td align="left"><code class="computeroutput">fmt(f(i,j))</code></td>
<td align="left">A container type, accessible using container traits</td>
<td align="left">Formats the result of the finder operation</td>
</tr></tbody>
</table></div>
</div>
<br class="table-break"><p>
Similarly to finders, formatters generalize format operations. When a finder is used to
select a part of the input, formatter takes this selection and performs some formatting
on it. Algorithms can abstract from formatting using a formatter.
</p>
<p>
<span class="bold"><strong>Examples</strong></span>
</p>
<p>
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
Formatter implemented as a class. This Formatter does not perform any formatting and
returns the match, repackaged. <code class="computeroutput">operator()</code>
is templated, so that the Formatter can be used on any Finder type.
<pre class="programlisting">
struct simple_formatter
{
template<typename FindResultT>
std::string operator()( const FindResultT& Match )
{
std::string Temp( Match.begin(), Match.end() );
return Temp;
}
};
</pre>
</li>
<li class="listitem">
Function Formatter. Similarly to Finder, Formatter can be any function object.
However, as a function, it can be used only with a specific Finder type.
<pre class="programlisting">
std::string simple_formatter( boost::iterator_range<std::string::const_iterator>& Match )
{
std::string Temp( Match.begin(), Match.end() );
return Temp;
}
</pre>
</li>
</ul></div>
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<td align="right"><div class="copyright-footer">Copyright © 2002-2004 Pavol Droba<p>Use, modification and distribution is subject to the Boost
Software License, Version 1.0. (See accompanying file
<code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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