/Src/Dependencies/Boost/doc/test/array2.xml

 1<section id="array.rationale">
 2   <title>Design Rationale</title>
 3
 4   <para>
 5      There was an important design tradeoff regarding the
 6      constructors: We could implement array as an "aggregate" (see
 7      Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would
 8      mean:
 9      <itemizedlist>
10         <listitem>
11            <simpara>
12               An array can be initialized with a
13               brace-enclosing, comma-separated list of initializers for the
14               elements of the container, written in increasing subscript
15               order:
16            </simpara>
17
18            <programlisting>
19               <classname>boost::array</classname>&lt;int,4&gt; a = { { 1, 2, 3 } };
20            </programlisting>
21
22            <simpara>
23               Note that if there are fewer elements in the
24               initializer list, then each remaining element gets
25               default-initialized (thus, it has a defined value).
26            </simpara>
27         </listitem>
28      </itemizedlist>
29   </para>
30
31   <para>
32      However, this approach has its drawbacks: <emphasis
33  role="bold">
34         passing no initializer list means that the elements
35         have an indetermined initial value
36      </emphasis>, because the rule says
37      that aggregates may have:
38      <itemizedlist>
39         <listitem>
40            <simpara>No user-declared constructors.</simpara>
41         </listitem>
42         <listitem>
43            <simpara>No private or protected non-static data members.</simpara>
44         </listitem>
45         <listitem>
46            <simpara>No base classes.</simpara>
47         </listitem>
48         <listitem>
49            <simpara>No virtual functions.</simpara>
50         </listitem>
51      </itemizedlist>
52   </para>
53
54   <para>Nevertheless, The current implementation uses this approach.</para>
55
56   <para>
57      Note that for standard conforming compilers it is possible to
58      use fewer braces (according to 8.5.1 (11) of the Standard). That is,
59      you can initialize an array as follows:
60   </para>
61
62   <programlisting>
63      <classname>boost::array</classname>&lt;int,4&gt; a = { 1, 2, 3 };
64   </programlisting>
65
66   <para>
67      I'd appreciate any constructive feedback. <emphasis
68  role="bold">
69         Please note: I don't have time to read all boost
70         mails. Thus, to make sure that feedback arrives to me, please send
71         me a copy of each mail regarding this class.
72      </emphasis>
73   </para>
74
75   <para>
76      The code is provided "as is" without expressed or implied
77      warranty.
78   </para>
79
80</section>
81
82