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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> |
| <dt><span class="section"><a href="concept.html#id2574797">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="id2574797"></a>Definitions</h3></div></div></div> |
| <div class="table"> |
| <a name="id2574803"></a><p class="title"><b>Table 21.13. 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="id2574938"></a><p class="title"><b>Table 21.14. 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" 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="id2575116"></a><p class="title"><b>Table 21.15. 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 formating |
| on it. Algorithms can abstract from formating using a formatter. |
| </p> |
| <p> |
| <span class="bold"><strong>Examples</strong></span> |
| </p> |
| <p> |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| Formatter implemented as a class. This Formatter does not perform any formating 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> |
| <p> |
| </p> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"><p><small>Last revised: June 19, 2008 at 13:07:24 +0100</small></p></td> |
| <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>) |
| </p> |
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