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<div><h2 class="title">
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<a name="array"></a>Chapter 5. Boost.Array</h2></div>
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<div><div class="author"><h3 class="author">
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<span class="firstname">Nicolai</span> <span class="surname">Josuttis</span>
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</h3></div></div>
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<div><p class="copyright">Copyright © 2001-2004 Nicolai M. Josuttis</p></div>
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<div><p class="copyright">Copyright © 2012 Marshall Clow</p></div>
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<a name="id-1.3.6.1.4"></a><p>Distributed under the Boost Software License, Version 1.0.
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(See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at
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<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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<p><b>Table of Contents</b></p>
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<dl class="toc">
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<dt><span class="section"><a href="array.html#array.intro">Introduction</a></span></dt>
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<dt><span class="section"><a href="array/reference.html">Reference</a></span></dt>
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<dd><dl><dt><span class="section"><a href="array/reference.html#header.boost.array_hpp">Header <boost/array.hpp></a></span></dt></dl></dd>
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<dt><span class="section"><a href="array/rationale.html">Design Rationale</a></span></dt>
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<dt><span class="section"><a href="array/more/info.html">For more information...</a></span></dt>
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<dt><span class="section"><a href="array/ack.html">Acknowledgements</a></span></dt>
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</dl>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="array.intro"></a>Introduction</h2></div></div></div>
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<p>The C++ Standard Template Library STL as part of the C++
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Standard Library provides a framework for processing algorithms on
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different kind of containers. However, ordinary arrays don't
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provide the interface of STL containers (although, they provide
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the iterator interface of STL containers).</p>
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<p>As replacement for ordinary arrays, the STL provides class
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<code class="computeroutput">std::vector</code>. However,
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<code class="computeroutput">std::vector<></code> provides
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the semantics of dynamic arrays. Thus, it manages data to be able
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to change the number of elements. This results in some overhead in
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case only arrays with static size are needed.</p>
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<p>In his book, <span class="emphasis"><em>Generic Programming and the
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STL</em></span>, Matthew H. Austern introduces a useful wrapper
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class for ordinary arrays with static size, called
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<code class="computeroutput">block</code>. It is safer and has no worse performance than
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ordinary arrays. In <span class="emphasis"><em>The C++ Programming
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Language</em></span>, 3rd edition, Bjarne Stroustrup introduces a
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similar class, called <code class="computeroutput">c_array</code>, which I (<a href="http://www.josuttis.com" target="_top">Nicolai Josuttis</a>) present
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slightly modified in my book <span class="emphasis"><em>The C++ Standard Library -
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A Tutorial and Reference</em></span>, called
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<code class="computeroutput">carray</code>. This is the essence of these approaches
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spiced with many feedback from <a href="http://www.boost.org" target="_top">boost</a>.</p>
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<p>After considering different names, we decided to name this
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class simply <code class="computeroutput"><a class="link" href="boost/array.html" title="Class template array">array</a></code>.</p>
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<p>Note that this class is suggested to be part of the next
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Technical Report, which will extend the C++ Standard (see
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<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1548.htm" target="_top">http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1548.htm</a>).</p>
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<p>Update: <code class="computeroutput">std::array</code> is (as of C++11) part of the C++ standard.
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The differences between <code class="computeroutput">boost::array</code> and <code class="computeroutput">std::array</code> are minimal.
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If you are using C++11, you should consider using <code class="computeroutput">std::array</code> instead of <code class="computeroutput">boost::array</code>.
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</p>
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<p>Class <code class="computeroutput"><a class="link" href="boost/array.html" title="Class template array">array</a></code> fulfills most
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but not all of the requirements of "reversible containers" (see
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Section 23.1, [lib.container.requirements] of the C++
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Standard). The reasons array is not an reversible STL container is
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because:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist compact" style="list-style-type: disc; ">
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<li class="listitem">No constructors are provided.</li>
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<li class="listitem">Elements may have an undetermined initial value (see <a class="xref" href="array/rationale.html" title="Design Rationale">the section called “Design Rationale”</a>).</li>
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<li class="listitem">
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<code class="computeroutput"><a class="link" href="boost/swap_1_3_5_5_2_1_3.html" title="Function swap">swap</a></code>() has no constant complexity.</li>
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<li class="listitem">
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<code class="computeroutput"><a class="link" href="boost/array.html#id-1_3_6_4_1_1_1_16_1-bb">size</a></code>() is always constant, based on the second template argument of the type.</li>
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<li class="listitem">The container provides no allocator support.</li>
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</ul></div>
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<p>
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</p>
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<p>It doesn't fulfill the requirements of a "sequence" (see Section 23.1.1, [lib.sequence.reqmts] of the C++ Standard), except that:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist compact" style="list-style-type: disc; ">
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<li class="listitem">
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<code class="computeroutput"><a class="link" href="boost/array.html#id-1_3_6_4_1_1_1_17_3-bb">front</a></code>() and <code class="computeroutput"><a class="link" href="boost/array.html#id-1_3_6_4_1_1_1_17_4-bb">back</a></code>() are provided.</li>
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<li class="listitem">
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<code class="computeroutput"><a class="link" href="boost/array.html#id-1_3_6_4_1_1_1_17_1-bb">operator[]</a></code> and <code class="computeroutput"><a class="link" href="boost/array.html#id-1_3_6_4_1_1_1_17_2-bb">at</a></code>() are provided.</li>
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</ul></div>
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<p>
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</p>
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