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<div class="title">Collation </div>  </div>
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<div class="textblock"><p>Boost.Locale provides a <a class="el" href="classboost_1_1locale_1_1collator.html">collator</a> class, derived from <code>std::collate</code>, that adds support for primary, secondary, tertiary, quaternary and identical comparison levels. They can be approximately defined as:</p>
<ol type="1">
<li>Primary &ndash; ignore accents and character case, comparing base letters only. For example "facade" and "Façade" are the same.</li>
<li>Secondary &ndash; ignore character case but consider accents. "facade" and "façade" are different but "Façade" and "façade" are the same.</li>
<li>Tertiary &ndash; consider both case and accents: "Façade" and "façade" are different. Ignore punctuation.</li>
<li>Quaternary &ndash; consider all case, accents, and punctuation. The words must be identical in terms of Unicode representation.</li>
<li>Identical &ndash; as quaternary, but compare code points as well.</li>
</ol>
<p>There are two ways of using the <a class="el" href="classboost_1_1locale_1_1collator.html">collator</a> facet: directly, by calling its member functions <a class="el" href="classboost_1_1locale_1_1collator.html#ab90dc7bb909a71d3cd9a5e8d7b2eb80e">compare</a>, <a class="el" href="classboost_1_1locale_1_1collator.html#a8dc6443fb193616332ca50f207a9b189">transform</a> and <a class="el" href="classboost_1_1locale_1_1collator.html#a89752e2023643f972b6cc8024340d5d4">hash</a>, or indirectly by using the <a class="el" href="structboost_1_1locale_1_1comparator.html">comparator</a> template class in STL algorithms.</p>
<p>For example:</p>
<div class="fragment"><div class="line">wstring a=L<span class="stringliteral">&quot;Façade&quot;</span>, b=L<span class="stringliteral">&quot;facade&quot;</span>;</div>
<div class="line"><span class="keywordtype">bool</span> eq = 0 == use_facet&lt;collator&lt;wchar_t&gt; &gt;(loc).compare(collator_base::secondary,a,b);</div>
<div class="line">wcout &lt;&lt; a &lt;&lt;L<span class="stringliteral">&quot; and &quot;</span>&lt;&lt;b&lt;&lt;L<span class="stringliteral">&quot; are &quot;</span> &lt;&lt; (eq ? L<span class="stringliteral">&quot;identical&quot;</span> : L<span class="stringliteral">&quot;different&quot;</span>)&lt;&lt;endl;</div>
</div><!-- fragment --><p><code>std::locale</code> is designed to be useful as a comparison class in STL collections and algorithms. To get similar functionality with comparison levels, you must use the comparator class.</p>
<div class="fragment"><div class="line">std::map&lt;std::string,std::string,comparator&lt;char,collator_base::secondary&gt; &gt; strings;</div>
<div class="line"><span class="comment">// Now strings uses the default system locale for string comparison</span></div>
</div><!-- fragment --><p>You can also set a specific locale or level when creating and using the <a class="el" href="structboost_1_1locale_1_1comparator.html">comparator</a> class:</p>
<div class="fragment"><div class="line">comparator&lt;char&gt; comp(some_locale,some_level);</div>
<div class="line">std::map&lt;std::string,std::string,comparator&lt;char&gt; &gt; strings(comp);</div>
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&copy; Copyright 2009-2012 Artyom Beilis,  Distributed under the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License</a>, Version 1.0.
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