ceph/src/boost/tools/boostbook/test/more/tests/libs/array.xml

   1 <?xml version="1.0" encoding="utf-8"?>
   2 <!--
   3     Copyright 2010 Daniel James.
   4
   5     Distributed under the Boost Software License, Version 1.0.
   6     (See accompanying file LICENSE_1_0.txt or copy at
   7     http://www.boost.org/LICENSE_1_0.txt)
   8 -->
   9 <!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
  10   "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
  11 <library name="Array" dirname="array" id="array" last-revision="$Date$">
  12   <libraryinfo>
  13     <author>
  14       <firstname>Nicolai</firstname>
  15       <surname>Josuttis</surname>
  16     </author>
  17
  18     <copyright>
  19       <year>2001</year>
  20       <year>2002</year>
  21       <year>2003</year>
  22       <year>2004</year>
  23       <holder>Nicolai M. Josuttis</holder>
  24     </copyright>
  25
  26     <legalnotice>
  27       <para>Distributed under the Boost Software License, Version 1.0.
  28       (See accompanying file <filename>LICENSE_1_0.txt</filename> or copy at
  29       <ulink
  30       url="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</ulink>)
  31       </para>
  32     </legalnotice>
  33
  34     <librarypurpose>STL compliant container wrapper for arrays of constant size</librarypurpose>
  35     <librarycategory name="category:containers"/>
  36   </libraryinfo>
  37
  38   <title>Boost.Array</title>
  39
  40   <section id="array.intro">
  41     <title>Introduction</title>
  42
  43     <using-namespace name="boost"/>
  44     <using-class name="array"/>
  45
  46     <para>The C++ Standard Template Library STL as part of the C++
  47     Standard Library provides a framework for processing algorithms on
  48     different kind of containers. However, ordinary arrays don't
  49     provide the interface of STL containers (although, they provide
  50     the iterator interface of STL containers).</para>
  51
  52     <para>As replacement for ordinary arrays, the STL provides class
  53     <code><classname>std::vector</classname></code>.  However,
  54     <code><classname>std::vector&lt;&gt;</classname></code> provides
  55     the semantics of dynamic arrays. Thus, it manages data to be able
  56     to change the number of elements. This results in some overhead in
  57     case only arrays with static size are needed.</para>
  58
  59     <para>In his book, <emphasis>Generic Programming and the
  60     STL</emphasis>, Matthew H. Austern introduces a useful wrapper
  61     class for ordinary arrays with static size, called
  62     <code>block</code>.  It is safer and has no worse performance than
  63     ordinary arrays. In <emphasis>The C++ Programming
  64     Language</emphasis>, 3rd edition, Bjarne Stroustrup introduces a
  65     similar class, called <code>c_array</code>, which I (<ulink
  66     url="http://www.josuttis.com">Nicolai Josuttis</ulink>) present
  67     slightly modified in my book <emphasis>The C++ Standard Library -
  68     A Tutorial and Reference</emphasis>, called
  69     <code>carray</code>. This is the essence of these approaches
  70     spiced with many feedback from <ulink
  71     url="http://www.boost.org">boost</ulink>.</para>
  72
  73     <para>After considering different names, we decided to name this
  74     class simply <code><classname>array</classname></code>.</para>
  75
  76     <para>Note that this class is suggested to be part of the next
  77     Technical Report, which will extend the C++ Standard (see
  78     <ulink url="http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1548.htm">http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1548.htm</ulink>).</para>
  79
  80     <para>Class <code><classname>array</classname></code> fulfills most
  81     but not all of the requirements of "reversible containers" (see
  82     Section 23.1, [lib.container.requirements] of the C++
  83     Standard). The reasons array is not an reversible STL container is
  84     because:
  85       <itemizedlist spacing="compact">
  86         <listitem><simpara>No constructors are provided.</simpara></listitem>
  87         <listitem><simpara>Elements may have an undetermined initial value (see <xref linkend="array.rationale"/>).</simpara></listitem>
  88         <listitem><simpara><functionname>swap</functionname>() has no constant complexity.</simpara></listitem>
  89         <listitem><simpara><methodname>size</methodname>() is always constant, based on the second template argument of the type.</simpara></listitem>
  90         <listitem><simpara>The container provides no allocator support.</simpara></listitem>
  91       </itemizedlist>
  92     </para>
  93
  94     <para>It doesn't fulfill the requirements of a "sequence" (see Section 23.1.1, [lib.sequence.reqmts] of the C++ Standard), except that:
  95       <itemizedlist spacing="compact">
  96         <listitem><simpara><methodname>front</methodname>() and <methodname>back</methodname>() are provided.</simpara></listitem>
  97         <listitem><simpara><methodname>operator[]</methodname> and <methodname>at</methodname>() are provided.</simpara></listitem>
  98       </itemizedlist>
  99     </para>
 100   </section>
 101
 102   <library-reference>
 103     <header name="boost/array.hpp">
 104       <namespace name="boost">
 105         <class name="array">
 106           <template>
 107             <template-type-parameter name="T"/>
 108             <template-nontype-parameter name="N">
 109               <type>std::size_t</type>
 110             </template-nontype-parameter>
 111           </template>
 112
 113           <purpose><para>STL compliant container wrapper for arrays of constant size</para></purpose>
 114           <typedef name="value_type">
 115             <type>T</type>
 116           </typedef>
 117           <typedef name="iterator">
 118              <type>T*</type>
 119           </typedef>
 120           <typedef name="const_iterator">
 121              <type>const T*</type>
 122           </typedef>
 123           <typedef name="reverse_iterator">
 124              <type><classname>std::reverse_iterator</classname>&lt;iterator&gt;</type>
 125           </typedef>
 126           <typedef name="const_reverse_iterator">
 127              <type><classname>std::reverse_iterator</classname>&lt;const_iterator&gt;</type>
 128           </typedef>
 129           <typedef name="reference">
 130              <type>T&amp;</type>
 131           </typedef>
 132           <typedef name="const_reference">
 133              <type>const T&amp;</type>
 134           </typedef>
 135           <typedef name="size_type">
 136              <type>std::size_t</type>
 137           </typedef>
 138           <typedef name="difference_type">
 139              <type>std::ptrdiff_t</type>
 140           </typedef>
 141
 142           <static-constant name="static_size">
 143             <type>size_type</type>
 144             <default>N</default>
 145           </static-constant>
 146
 147           <copy-assignment>
 148             <template>
 149               <template-type-parameter name="U"/>
 150             </template>
 151             <parameter name="other">
 152               <paramtype>const <classname>array</classname>&lt;U, N&gt;&amp;</paramtype>
 153             </parameter>
 154             <effects><simpara><code>std::copy(rhs.<methodname>begin</methodname>(),rhs.<methodname>end</methodname>(), <methodname>begin</methodname>())</code></simpara></effects>
 155           </copy-assignment>
 156
 157           <method-group name="iterator support">
 158             <overloaded-method name="begin">
 159               <signature>
 160                 <type>iterator</type>
 161               </signature>
 162               <signature cv="const">
 163                 <type>const_iterator</type>
 164               </signature>
 165
 166               <returns><simpara>iterator for the first element</simpara></returns>
 167               <throws><simpara>will not throw</simpara></throws>
 168             </overloaded-method>
 169
 170             <overloaded-method name="end">
 171               <signature>
 172                 <type>iterator</type>
 173               </signature>
 174               <signature cv="const">
 175                 <type>const_iterator</type>
 176               </signature>
 177
 178               <returns><simpara>iterator for position after the last element</simpara></returns>
 179               <throws><simpara>will not throw</simpara></throws>
 180             </overloaded-method>
 181           </method-group>
 182
 183           <method-group name="reverse iterator support">
 184             <overloaded-method name="rbegin">
 185               <signature>
 186                 <type>reverse_iterator</type>
 187               </signature>
 188               <signature cv="const">
 189                 <type>const_reverse_iterator</type>
 190               </signature>
 191
 192               <returns><simpara>reverse iterator for the first element of reverse iteration</simpara></returns>
 193             </overloaded-method>
 194
 195             <overloaded-method name="rend">
 196               <signature>
 197                 <type>reverse_iterator</type>
 198               </signature>
 199               <signature cv="const">
 200                 <type>const_reverse_iterator</type>
 201               </signature>
 202
 203               <returns><simpara>reverse iterator for position after the last element in reverse iteration</simpara></returns>
 204             </overloaded-method>
 205           </method-group>
 206
 207           <method-group name="capacity">
 208             <method name="size">
 209               <type>size_type</type>
 210               <returns><simpara><code>N</code></simpara></returns>
 211             </method>
 212             <method name="empty">
 213               <type>bool</type>
 214               <returns><simpara><code>N==0</code></simpara></returns>
 215               <throws><simpara>will not throw</simpara></throws>
 216             </method>
 217             <method name="max_size">
 218               <type>size_type</type>
 219               <returns><simpara><code>N</code></simpara></returns>
 220               <throws><simpara>will not throw</simpara></throws>
 221             </method>
 222           </method-group>
 223
 224           <method-group name="element access">
 225             <overloaded-method name="operator[]">
 226               <signature>
 227                 <type>reference</type>
 228                 <parameter name="i">
 229                   <paramtype>size_type</paramtype>
 230                 </parameter>
 231               </signature>
 232
 233               <signature cv="const">
 234                 <type>const_reference</type>
 235                 <parameter name="i">
 236                   <paramtype>size_type</paramtype>
 237                 </parameter>
 238               </signature>
 239
 240               <requires><simpara><code>i &lt; N</code></simpara></requires>
 241               <returns><simpara>element with index <code>i</code></simpara></returns>
 242               <throws><simpara>will not throw.</simpara></throws>
 243             </overloaded-method>
 244
 245             <overloaded-method name="at">
 246               <signature>
 247                 <type>reference</type>
 248                 <parameter name="i">
 249                   <paramtype>size_type</paramtype>
 250                 </parameter>
 251               </signature>
 252
 253               <signature cv="const">
 254                 <type>const_reference</type>
 255                 <parameter name="i">
 256                   <paramtype>size_type</paramtype>
 257                 </parameter>
 258               </signature>
 259
 260               <returns><simpara>element with index <code>i</code></simpara></returns>
 261               <throws><simpara><code><classname>std::range_error</classname></code> if <code>i &gt;= N</code></simpara></throws>
 262             </overloaded-method>
 263
 264             <overloaded-method name="front">
 265               <signature>
 266                 <type>reference</type>
 267               </signature>
 268               <signature cv="const">
 269                 <type>const_reference</type>
 270               </signature>
 271               <requires><simpara><code>N &gt; 0</code></simpara></requires>
 272               <returns><simpara>the first element</simpara></returns>
 273               <throws><simpara>will not throw</simpara></throws>
 274             </overloaded-method>
 275
 276             <overloaded-method name="back">
 277               <signature>
 278                 <type>reference</type>
 279               </signature>
 280               <signature cv="const">
 281                 <type>const_reference</type>
 282               </signature>
 283               <requires><simpara><code>N &gt; 0</code></simpara></requires>
 284               <returns><simpara>the last element</simpara></returns>
 285               <throws><simpara>will not throw</simpara></throws>
 286             </overloaded-method>
 287
 288             <method name="data" cv="const">
 289               <type>const T*</type>
 290               <returns><simpara><code>elems</code></simpara></returns>
 291               <throws><simpara>will not throw</simpara></throws>
 292             </method>
 293
 294            <method name="c_array">
 295               <type>T*</type>
 296               <returns><simpara><code>elems</code></simpara></returns>
 297               <throws><simpara>will not throw</simpara></throws>
 298             </method>
 299           </method-group>
 300
 301           <method-group name="modifiers">
 302             <method name="swap">
 303               <type>void</type>
 304               <parameter name="other">
 305                 <paramtype><classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 306               </parameter>
 307               <effects><simpara><code>std::swap_ranges(<methodname>begin</methodname>(), <methodname>end</methodname>(), other.<methodname>begin</methodname>())</code></simpara></effects>
 308               <complexity><simpara>linear in <code>N</code></simpara></complexity>
 309             </method>
 310             <method name="assign">
 311               <type>void</type>
 312               <parameter name="value">
 313                 <paramtype>const T&amp;</paramtype>
 314               </parameter>
 315               <effects><simpara><code>std::fill_n(<methodname>begin</methodname>(), N, value)</code></simpara></effects>
 316             </method>
 317           </method-group>
 318
 319           <data-member name="elems[N]"> <!-- HACK -->
 320             <type>T</type>
 321           </data-member>
 322
 323           <free-function-group name="specialized algorithms">
 324             <function name="swap">
 325               <template>
 326                 <template-type-parameter name="T"/>
 327                 <template-nontype-parameter name="N">
 328                   <type>std::size_t</type>
 329                 </template-nontype-parameter>
 330               </template>
 331
 332               <type>void</type>
 333
 334               <parameter name="x">
 335                 <paramtype><classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 336               </parameter>
 337               <parameter name="y">
 338                 <paramtype><classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 339               </parameter>
 340
 341               <effects><simpara><code>x.<methodname>swap</methodname>(y)</code></simpara></effects>
 342               <throws><simpara>will not throw.</simpara></throws>
 343             </function>
 344           </free-function-group>
 345
 346           <free-function-group name="comparisons">
 347             <function name="operator==">
 348               <template>
 349                 <template-type-parameter name="T"/>
 350                 <template-nontype-parameter name="N">
 351                   <type>std::size_t</type>
 352                 </template-nontype-parameter>
 353               </template>
 354
 355               <type>bool</type>
 356
 357               <parameter name="x">
 358                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 359               </parameter>
 360               <parameter name="y">
 361                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 362               </parameter>
 363
 364               <returns><simpara><code>std::equal(x.<methodname>begin</methodname>(), x.<methodname>end</methodname>(), y.<methodname>begin</methodname>())</code></simpara>
 365               </returns>
 366             </function>
 367
 368             <function name="operator!=">
 369               <template>
 370                 <template-type-parameter name="T"/>
 371                 <template-nontype-parameter name="N">
 372                   <type>std::size_t</type>
 373                 </template-nontype-parameter>
 374               </template>
 375
 376               <type>bool</type>
 377
 378               <parameter name="x">
 379                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 380               </parameter>
 381               <parameter name="y">
 382                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 383               </parameter>
 384
 385               <returns><simpara><code>!(x == y)</code></simpara>
 386               </returns>
 387             </function>
 388
 389             <function name="operator&lt;">
 390               <template>
 391                 <template-type-parameter name="T"/>
 392                 <template-nontype-parameter name="N">
 393                   <type>std::size_t</type>
 394                 </template-nontype-parameter>
 395               </template>
 396
 397               <type>bool</type>
 398
 399               <parameter name="x">
 400                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 401               </parameter>
 402               <parameter name="y">
 403                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 404               </parameter>
 405
 406               <returns><simpara><code>std::lexicographical_compare(x.<methodname>begin</methodname>(), x.<methodname>end</methodname>(), y.<methodname>begin</methodname>(), y.<methodname>end</methodname>())</code></simpara>
 407               </returns>
 408             </function>
 409
 410             <function name="operator&gt;">
 411               <template>
 412                 <template-type-parameter name="T"/>
 413                 <template-nontype-parameter name="N">
 414                   <type>std::size_t</type>
 415                 </template-nontype-parameter>
 416               </template>
 417
 418               <type>bool</type>
 419
 420               <parameter name="x">
 421                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 422               </parameter>
 423               <parameter name="y">
 424                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 425               </parameter>
 426
 427               <returns><simpara><code>y &lt; x</code></simpara></returns>
 428             </function>
 429
 430             <function name="operator&lt;=">
 431               <template>
 432                 <template-type-parameter name="T"/>
 433                 <template-nontype-parameter name="N">
 434                   <type>std::size_t</type>
 435                 </template-nontype-parameter>
 436               </template>
 437
 438               <type>bool</type>
 439
 440               <parameter name="x">
 441                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 442               </parameter>
 443               <parameter name="y">
 444                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 445               </parameter>
 446
 447               <returns><simpara><code>!(y &lt; x)</code></simpara></returns>
 448             </function>
 449
 450             <function name="operator&gt;=">
 451               <template>
 452                 <template-type-parameter name="T"/>
 453                 <template-nontype-parameter name="N">
 454                   <type>std::size_t</type>
 455                 </template-nontype-parameter>
 456               </template>
 457
 458               <type>bool</type>
 459
 460               <parameter name="x">
 461                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 462               </parameter>
 463               <parameter name="y">
 464                 <paramtype>const <classname>array</classname>&lt;T, N&gt;&amp;</paramtype>
 465               </parameter>
 466
 467               <returns><simpara><code>!(x &lt; y)</code></simpara></returns>
 468             </function>
 469           </free-function-group>
 470         </class>
 471       </namespace>
 472     </header>
 473   </library-reference>
 474
 475 <section id="array.rationale">
 476   <title>Design Rationale</title>
 477
 478   <para>There was an important design tradeoff regarding the
 479   constructors: We could implement array as an "aggregate" (see
 480   Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would
 481   mean:
 482     <itemizedlist>
 483       <listitem><simpara>An array can be initialized with a
 484       brace-enclosing, comma-separated list of initializers for the
 485       elements of the container, written in increasing subscript
 486       order:</simpara>
 487
 488       <programlisting><classname>boost::array</classname>&lt;int,4&gt; a = { { 1, 2, 3 } };</programlisting>
 489
 490       <simpara>Note that if there are fewer elements in the
 491       initializer list, then each remaining element gets
 492       default-initialized (thus, it has a defined value).</simpara>
 493   </listitem></itemizedlist></para>
 494
 495   <para>However, this approach has its drawbacks: <emphasis
 496   role="bold"> passing no initializer list means that the elements
 497   have an indetermined initial value</emphasis>, because the rule says
 498   that aggregates may have:
 499     <itemizedlist>
 500       <listitem><simpara>No user-declared constructors.</simpara></listitem>
 501       <listitem><simpara>No private or protected non-static data members.</simpara></listitem>
 502       <listitem><simpara>No base classes.</simpara></listitem>
 503       <listitem><simpara>No virtual functions.</simpara></listitem>
 504     </itemizedlist>
 505   </para>
 506
 507   <para>Nevertheless, The current implementation uses this approach.</para>
 508
 509   <para>Note that for standard conforming compilers it is possible to
 510   use fewer braces (according to 8.5.1 (11) of the Standard). That is,
 511   you can initialize an array as follows:</para>
 512
 513 <programlisting>
 514 <classname>boost::array</classname>&lt;int,4&gt; a = { 1, 2, 3 };
 515 </programlisting>
 516
 517   <para>I'd appreciate any constructive feedback. <emphasis
 518   role="bold">Please note: I don't have time to read all boost
 519   mails. Thus, to make sure that feedback arrives to me, please send
 520   me a copy of each mail regarding this class.</emphasis></para>
 521
 522   <para>The code is provided "as is" without expressed or implied
 523   warranty.</para>
 524
 525 </section>
 526
 527 <section id="array.more.info">
 528   <title>For more information...</title>
 529   <para>To find more details about using ordinary arrays in C++ and
 530   the framework of the STL, see e.g.
 531
 532     <literallayout>The C++ Standard Library - A Tutorial and Reference
 533 by Nicolai M. Josuttis
 534 Addison Wesley Longman, 1999
 535 ISBN 0-201-37926-0</literallayout>
 536    </para>
 537
 538   <para><ulink url="http://www.josuttis.com/">Home Page of Nicolai
 539   Josuttis</ulink></para>
 540 </section>
 541
 542 <section id="array.ack">
 543   <title>Acknowledgements</title>
 544
 545   <para>Doug Gregor ported the documentation to the BoostBook format.</para>
 546 </section>
 547
 548 <!-- Notes:
 549    empty() should return N != 0
 550    size(), empty(), max_size() should be const
 551    -->
 552
 553 </library>