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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="array.rationale"></a>Design Rationale</h2></div></div></div> |
| <p>There was an important design tradeoff regarding the |
| constructors: We could implement array as an "aggregate" (see |
| Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would |
| mean: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| <p class="simpara">An array can be initialized with a |
| brace-enclosing, comma-separated list of initializers for the |
| elements of the container, written in increasing subscript |
| order:</p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../boost/array.html" title="Class template array">boost::array</a></code><int,4> a = { { 1, 2, 3 } };</pre> |
| <p class="simpara">Note that if there are fewer elements in the |
| initializer list, then each remaining element gets |
| default-initialized (thus, it has a defined value).</p> |
| </li></ul></div> |
| <p>However, this approach has its drawbacks: <span class="bold"><strong> passing no initializer list means that the elements |
| have an indetermined initial value</strong></span>, because the rule says |
| that aggregates may have: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem">No user-declared constructors.</li> |
| <li class="listitem">No private or protected non-static data members.</li> |
| <li class="listitem">No base classes.</li> |
| <li class="listitem">No virtual functions.</li> |
| </ul></div> |
| <p> |
| </p> |
| <p>Nevertheless, The current implementation uses this approach.</p> |
| <p>Note that for standard conforming compilers it is possible to |
| use fewer braces (according to 8.5.1 (11) of the Standard). That is, |
| you can initialize an array as follows:</p> |
| <pre class="programlisting"> |
| <code class="computeroutput"><a class="link" href="../boost/array.html" title="Class template array">boost::array</a></code><int,4> a = { 1, 2, 3 }; |
| </pre> |
| <p>I'd appreciate any constructive feedback. <span class="bold"><strong>Please note: I don't have time to read all boost |
| mails. Thus, to make sure that feedback arrives to me, please send |
| me a copy of each mail regarding this class.</strong></span></p> |
| <p>The code is provided "as is" without expressed or implied |
| warranty.</p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2001-2004 Nicolai M. Josuttis<p>Distributed under 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>) |
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