1<section id="array.intro"> 2 <title>Introduction</title> 3 4 <using-namespace name="boost"/> 5 <using-class name="array"/> 6 7 <para>The C++ Standard Template Library STL as part of the C++ 8 Standard Library provides a framework for processing algorithms on 9 different kind of containers. However, ordinary arrays don't 10 provide the interface of STL containers (although, they provide 11 the iterator interface of STL containers).</para> 12 13 <para>As replacement for ordinary arrays, the STL provides class 14 <code><classname>std::vector</classname></code>. However, 15 <code><classname>std::vector<></classname></code> provides 16 the semantics of dynamic arrays. Thus, it manages data to be able 17 to change the number of elements. This results in some overhead in 18 case only arrays with static size are needed.</para> 19 20 <para>In his book, <emphasis>Generic Programming and the 21 STL</emphasis>, Matthew H. Austern introduces a useful wrapper 22 class for ordinary arrays with static size, called 23 <code>block</code>. It is safer and has no worse performance than 24 ordinary arrays. In <emphasis>The C++ Programming 25 Language</emphasis>, 3rd edition, Bjarne Stroustrup introduces a 26 similar class, called <code>c_array</code>, which I (<ulink 27 url="http://www.josuttis.com">Nicolai Josuttis</ulink>) present 28 slightly modified in my book <emphasis>The C++ Standard Library - 29 A Tutorial and Reference</emphasis>, called 30 <code>carray</code>. This is the essence of these approaches 31 spiced with many feedback from <ulink 32 url="http://www.boost.org">boost</ulink>.</para> 33 34 <para>After considering different names, we decided to name this 35 class simply <code><classname>array</classname></code>.</para> 36 37 <para>Note that this class is suggested to be part of the next 38 Technical Report, which will extend the C++ Standard (see 39 <ulink url="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1548.htm">http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1548.htm</ulink>).</para> 40 41 <para>Class <code><classname>array</classname></code> fulfills most 42 but not all of the requirements of "reversible containers" (see 43 Section 23.1, [lib.container.requirements] of the C++ 44 Standard). The reasons array is not an reversible STL container is 45 because: 46 <itemizedlist spacing="compact"> 47 <listitem><simpara>No constructors are provided.</simpara></listitem> 48 <listitem><simpara>Elements may have an undetermined initial value (see <xref linkend="array.rationale"/>).</simpara></listitem> 49 <listitem><simpara><functionname>swap</functionname>() has no constant complexity.</simpara></listitem> 50 <listitem><simpara><methodname>size</methodname>() is always constant, based on the second template argument of the type.</simpara></listitem> 51 <listitem><simpara>The container provides no allocator support.</simpara></listitem> 52 </itemizedlist> 53 </para> 54 55 <para>It doesn't fulfill the requirements of a "sequence" (see Section 23.1.1, [lib.sequence.reqmts] of the C++ Standard), except that: 56 <itemizedlist spacing="compact"> 57 <listitem><simpara><methodname>front</methodname>() and <methodname>back</methodname>() are provided.</simpara></listitem> 58 <listitem><simpara><methodname>operator[]</methodname> and <methodname>at</methodname>() are provided.</simpara></listitem> 59 </itemizedlist> 60 </para> 61 </section> 62 63 64 65