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<title>Extended functionality</title>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="container.extended_functionality"></a><a class="link" href="extended_functionality.html" title="Extended functionality">Extended functionality</a>
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<div class="toc"><dl class="toc"><dt><span class="section"><a href="extended_functionality.html#container.extended_functionality.default_initialialization">Default
initialization for vector-like containers</a></span></dt></dl></div>
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<div class="titlepage"><div><div><h3 class="title">
<a name="container.extended_functionality.default_initialialization"></a><a class="link" href="extended_functionality.html#container.extended_functionality.default_initialialization" title="Default initialization for vector-like containers">Default
initialization for vector-like containers</a>
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<p>
STL and most other containers value initialize new elements in common operations
like <code class="computeroutput"><span class="identifier">vector</span><span class="special">::</span><span class="identifier">resize</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">)</span></code> or <code class="computeroutput"><span class="keyword">explicit</span>
<span class="identifier">vector</span><span class="special">::</span><span class="identifier">vector</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">)</span></code>.
</p>
<p>
In some performance-sensitive environments, where vectors are used as a replacement
for variable-size buffers for file or network operations, <a href="http://en.cppreference.com/w/cpp/language/value_initialization" target="_top">value
initialization</a> is a cost that is not negligible as elements are going
to be overwritten by an external source shortly after new elements are added
to the container.
</p>
<p>
<span class="bold"><strong>Boost.Container</strong></span> offers two new members for
<code class="computeroutput"><span class="identifier">vector</span></code>, <code class="computeroutput"><span class="identifier">static_vector</span></code>
and <code class="computeroutput"><span class="identifier">stable_vector</span></code>: <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">container</span><span class="special">::</span><span class="identifier">container</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">default_init_t</span><span class="special">)</span></code> and <code class="computeroutput"><span class="keyword">explicit</span>
<span class="identifier">container</span><span class="special">::</span><span class="identifier">resize</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">default_init_t</span><span class="special">)</span></code>, where new elements are constructed using
<a href="http://en.cppreference.com/w/cpp/language/default_initialization" target="_top">default
initialization</a>.
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<td align="right"><div class="copyright-footer">Copyright © 2009-2013 Ion Gaztanaga<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt 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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