83 lines
2.5 KiB
XML
83 lines
2.5 KiB
XML
<section id="array.rationale">
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<title>Design Rationale</title>
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<para>
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There was an important design tradeoff regarding the
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constructors: We could implement array as an "aggregate" (see
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Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would
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mean:
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<itemizedlist>
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<listitem>
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<simpara>
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An array can be initialized with a
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brace-enclosing, comma-separated list of initializers for the
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elements of the container, written in increasing subscript
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order:
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</simpara>
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<programlisting>
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<classname>boost::array</classname><int,4> a = { { 1, 2, 3 } };
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</programlisting>
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<simpara>
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Note that if there are fewer elements in the
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initializer list, then each remaining element gets
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default-initialized (thus, it has a defined value).
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</simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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However, this approach has its drawbacks: <emphasis
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role="bold">
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passing no initializer list means that the elements
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have an indetermined initial value
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</emphasis>, because the rule says
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that aggregates may have:
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<itemizedlist>
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<listitem>
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<simpara>No user-declared constructors.</simpara>
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</listitem>
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<listitem>
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<simpara>No private or protected non-static data members.</simpara>
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</listitem>
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<listitem>
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<simpara>No base classes.</simpara>
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</listitem>
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<listitem>
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<simpara>No virtual functions.</simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>Nevertheless, The current implementation uses this approach.</para>
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<para>
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Note that for standard conforming compilers it is possible to
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use fewer braces (according to 8.5.1 (11) of the Standard). That is,
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you can initialize an array as follows:
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</para>
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<programlisting>
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<classname>boost::array</classname><int,4> a = { 1, 2, 3 };
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</programlisting>
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<para>
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I'd appreciate any constructive feedback. <emphasis
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role="bold">
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Please note: I don't have time to read all boost
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mails. Thus, to make sure that feedback arrives to me, please send
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me a copy of each mail regarding this class.
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</emphasis>
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</para>
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<para>
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The code is provided "as is" without expressed or implied
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warranty.
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</para>
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</section>
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