libs/multi_index/doc/reference/key_extraction.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN">
   2
   3 <html>
   4 <head>
   5 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
   6 <title>Boost.MultiIndex Documentation - Key extraction reference</title>
   7 <link rel="stylesheet" href="../style.css" type="text/css">
   8 <link rel="start" href="../index.html">
   9 <link rel="prev" href="rnd_indices.html">
  10 <link rel="up" href="index.html">
  11 <link rel="next" href="../compiler_specifics.html">
  12 </head>
  13
  14 <body>
  15 <h1><img src="../../../../boost.png" alt="boost.png (6897 bytes)" align=
  16 "middle" width="277" height="86">Boost.MultiIndex Key extraction reference</h1>
  17
  18 <div class="prev_link"><a href="rnd_indices.html"><img src="../prev.gif" alt="random access indices" border="0"><br>
  19 Random access indices
  20 </a></div>
  21 <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex reference" border="0"><br>
  22 Boost.MultiIndex reference
  23 </a></div>
  24 <div class="next_link"><a href="../compiler_specifics.html"><img src="../next.gif" alt="compiler specifics" border="0"><br>
  25 Compiler specifics
  26 </a></div><br clear="all" style="clear: all;">
  27
  28 <hr>
  29
  30 <h2>Contents</h2>
  31
  32 <ul>
  33   <li><a href="#key_extractors">Key Extractors</a>
  34     <ul>
  35       <li><a href="#chained_pointers">Chained pointers</a></li>
  36     </ul>
  37   </li>
  38   <li><a href="#synopsis">Header
  39     <code>"boost/multi_index/key_extractors.hpp"</code> synopsis</a>
  40   </li>
  41   <li><a href="#identity_synopsis">Header
  42     <code>"boost/multi_index/identity.hpp"</code> synopsis</a>
  43     <ul>
  44       <li><a href="#identity">Class template <code>identity</code></a></li>
  45     </ul>
  46   </li>
  47   <li><a href="#member_synopsis">Header
  48     <code>"boost/multi_index/member.hpp"</code> synopsis</a>
  49     <ul>
  50       <li><a href="#member">Class template <code>member</code></a></li>
  51       <li><a href="#member_offset">Class template <code>member_offset</code></a></li>
  52       <li><a href="#boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></li>
  53     </ul>
  54   </li>
  55   <li><a href="#mem_fun_synopsis">Header
  56     <code>"boost/multi_index/mem_fun.hpp"</code> synopsis</a>
  57     <ul>
  58       <li><a href="#const_mem_fun">Class template <code>const_mem_fun</code></a></li>
  59       <li><a href="#mem_fun">Class template <code>mem_fun</code></a></li>
  60       <li><a href="#const_mem_fun_explicit">Class templates <code>const_mem_fun_explicit</code> and <code>mem_fun_explicit</code></a></li>
  61       <li><a href="#boost_multi_index_const_mem_fun">Macros <code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code> and <code>BOOST_MULTI_INDEX_MEM_FUN</code></a></li>
  62     </ul>
  63   </li>
  64   <li><a href="#global_fun_synopsis">Header
  65     <code>"boost/multi_index/global_fun.hpp"</code> synopsis</a>
  66     <ul>
  67       <li><a href="#global_fun">Class template <code>global_fun</code></a></li>
  68     </ul>
  69   </li>
  70   <li><a href="#composite_key_synopsis">Header
  71     <code>"boost/multi_index/composite_key.hpp"</code> synopsis</a>
  72     <ul>
  73       <li><a href="#composite_key">Class template <code>composite_key</code></a></li>
  74       <li><a href="#composite_key_result">Class template <code>composite_key_result</code></a></li>
  75       <li><a href="#ckey_result_equality">Equality</a>
  76         <ul>
  77           <li><a href="#composite_key_equal_to">Class template <code>composite_key_equal_to</code></a></li>
  78           <li><a href="#composite_key_result_equal_to">Class template <code>composite_key_result_equal_to</code></a></li>
  79           <li><a href="#equal_to_composite_key_result">Specialization of <code>std::equal_to</code> for <code>composite_key</code> results</a></li>
  80         </ul>
  81       </li>
  82       <li><a href="#ckey_result_comparison">Comparison</a>
  83         <ul>
  84           <li><a href="#composite_key_compare">Class template <code>composite_key_compare</code></a></li>
  85           <li><a href="#composite_key_result_less">Class template <code>composite_key_result_less</code></a></li>
  86           <li><a href="#composite_key_result_greater">Class template <code>composite_key_result_greater</code></a></li>
  87           <li><a href="#less_composite_key_result">Specialization of <code>std::less</code> for <code>composite_key</code> results</a></li>
  88           <li><a href="#greater_composite_key_result">Specialization of <code>std::greater</code> for <code>composite_key</code> results</a></li>
  89         </ul>
  90       </li>
  91       <li><a href="#ckey_result_hashing">Hashing</a>
  92         <ul>
  93           <li><a href="#composite_key_hash">Class template <code>composite_key_hash</code></a></li>
  94           <li><a href="#composite_key_result_hash">Class template <code>composite_key_result_hash</code></a></li>
  95           <li><a href="#hash_composite_key_result">Specialization of <code>boost::hash</code> for <code>composite_key</code> results</a></li>
  96         </ul>
  97       </li>
  98       <li><a href="#ckey_result_semantics">Semantics of <code>composite_key_result</code></a></li>
  99     </ul>
 100   </li>
 101 </ul>
 102
 103 <h2><a name="key_extractors">Key Extractors</a></h2>
 104
 105 <p>
 106 Key extraction classes are used by
 107 <a href="indices.html#key_based_indices">key-based indices</a> to
 108 obtain the indexing keys from the elements of a <code>multi_index_container</code>.
 109 A <code>CopyConstructible</code> and <code>CopyAssignable</code>
 110 class <code>KeyFromValue</code> is said to be a key extractor from a
 111 type <code>Type</code> if
 112 <ol>
 113   <li>the type <code>KeyFromValue::result_type</code> is defined,</li>
 114   <li><code>k1(ca)</code> is defined and returns a value convertible
 115     to <code>const KeyFromValue::result_type&amp;</code>,</li>
 116   <li>if <code>k2</code> is a copy of <code>k1</code>, <code>k1(ca)</code> is the
 117     same value as <code>k2(ca)</code>,</li>
 118 </ol>
 119 for every <code>k1</code>, <code>k2</code> of type <code>const KeyFromValue</code>,
 120 and <code>ca</code> of type <code>const Type&amp;</code>.
 121 </p>
 122
 123 <p>
 124 Additionally, <code>KeyFromValue</code> is a <i>read/write</i> key extractor
 125 if the following extra conditions are met:
 126 <ol>
 127   <li><code>k1(a)</code> is defined and returns a value convertible
 128     to <code>KeyFromValue::result_type&amp;</code>,</li>
 129   <li><code>const_cast&lt;const KeyFromValue::result_type&amp;>(k1(a))</code>
 130     is the same  value as
 131     <code>k1(const_cast&lt;const Type&amp;>(a))</code>,</li>
 132 </ol>
 133 for every <code>k1</code> of type <code>const KeyFromValue</code> and
 134 <code>a</code> of type <code>Type&amp;</code>.
 135 </p>
 136
 137 <p>
 138 Boost.MultiIndex provides six general-purpose key extractors:
 139 <ul>
 140   <li><a href="#identity"><code>identity</code></a>,</li>
 141   <li><a href="#member"><code>member</code></a>,</li>
 142   <li><a href="#const_mem_fun"><code>const_mem_fun</code></a>,</li>
 143   <li><a href="#mem_fun"><code>mem_fun</code></a>,</li>
 144   <li><a href="#global_fun"><code>global_fun</code></a> and</li>
 145   <li><a href="#composite_key"><code>composite_key</code></a>.</li>
 146 </ul>
 147 </p>
 148
 149 <h3><a name="chained_pointers">Chained pointers</a></h3>
 150
 151 <p>
 152 The key extractors provided by Boost.MultiIndex are templatized according
 153 to the type <code>Type</code> and serve to extract keys not only from objects
 154 of type <code>Type</code>, but also from reference wrappers provided by
 155 <a href="../../../../doc/html/ref.html">Boost.Ref</a> and from <i>chained pointers</i>
 156 to <code>Type</code> (or to reference wrappers of <code>Type</code>): a chained pointer
 157 is any type <code>P</code> such that, for an object <code>p</code> of type
 158 <code>const P</code>
 159 <ul>
 160   <li><code>*p</code> yields an object of type <code>Type&amp;</code> or
 161     <code>boost::reference_wrapper&lt;Type></code>, OR</li>
 162   <li><code>*p</code> yields a chained pointer to <code>Type</code>,</li>
 163 </ul>
 164 that is, chained pointers are arbitrary compositions of pointer-like objects
 165 ultimately dereferencing to values of <code>Type&amp;</code> or
 166 <code>boost::reference_wrapper&lt;Type></code>.
 167 <p>
 168
 169 <h2><a name="synopsis">Header
 170 <a href="../../../../boost/multi_index/key_extractors.hpp">
 171 <code>"boost/multi_index/key_extractors.hpp"</code></a> synopsis</a>
 172 </h2>
 173
 174 <blockquote><pre>
 175 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>identity</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
 176 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>member</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
 177 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>mem_fun</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
 178 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>global_fun</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
 179 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>composite_key</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
 180 </pre></blockquote>
 181
 182 <p>
 183 This header includes all the key extractors provided by Boost.MultiIndex.
 184 </p>
 185
 186 <h2>
 187 <a name="identity_synopsis">Header
 188 <a href="../../../../boost/multi_index/identity.hpp">
 189 <code>"boost/multi_index/identity.hpp"</code></a> synopsis</a></h2>
 190
 191 <blockquote><pre>
 192 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 193
 194 <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
 195
 196 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>&gt;</span> <span class=keyword>struct</span> <span class=identifier>identity</span><span class=special>;</span>
 197
 198 <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
 199
 200 <span class=special>}</span> <span class=comment>// namespace boost</span>
 201 </pre></blockquote>
 202
 203 <h3><a name="identity">Class template <code>identity</code></a></h3>
 204
 205 <p>
 206 <code>identity</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 207 that acts as a do-nothing identity functor.
 208 </p>
 209
 210 <blockquote><pre>
 211 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>&gt;</span>
 212 <span class=keyword>struct</span> <span class=identifier>identity</span>
 213 <span class=special>{</span>
 214   <span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span>
 215
 216   <span class=comment>// only provided if const ChainedPtr&amp; is not convertible to const Type&amp;</span>
 217   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>&gt;</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 218
 219   <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 220   <span class=identifier>Type</span><span class=special>&amp;</span>       <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Type</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const
 221
 222   // only provided if Type is non-const</span>
 223   <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 224
 225   <span class=comment>// only provided if Type is const</span>
 226   <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span>
 227     <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>remove_const</span><span class=special>&lt;</span><span class=identifier>Type</span><span class=special>&gt;::</span><span class=identifier>type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 228
 229   <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=identifier>Type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 230 <span class=special>};</span>
 231 </pre></blockquote>
 232
 233 <p>
 234 <code>identity&lt;Type></code> is a model of:
 235 <ul>
 236   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 237     from <code>Type</code>,</li>
 238   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 239     from <code>reference_wrapper&lt;const Type></code>,</li>
 240   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 241     from <code>reference_wrapper&lt;Type></code>,</li>
 242   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 243     from any <a href="#chained_pointers">chained pointer</a> to
 244     <code>const Type</code>,</li>
 245   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 246     from any <a href="#chained_pointers">chained pointer</a>
 247     to <code>Type</code>.</li>
 248 </ul>
 249 </p>
 250
 251 <h4><code>identity</code> members</h4>
 252
 253 <code>template&lt;typename ChainedPtr> Type&amp; operator()(const ChainedPtr&amp; x)const;</code>
 254
 255 <blockquote>
 256 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 257 type to <code>Type</code>.<br>
 258 <b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>.
 259 </blockquote>
 260
 261 <code>const Type&amp; operator()(const Type&amp; x)const;</code>
 262
 263 <blockquote>
 264 <b>Returns:</b> <code>x</code>.
 265 </blockquote>
 266
 267 <code>Type&amp; operator()(Type&amp; x)const;</code>
 268
 269 <blockquote>
 270 <b>Returns:</b> <code>x</code>.
 271 </blockquote>
 272
 273 <code>const Type&amp; operator()(const reference_wrapper&lt;const Type>&amp; x)const;</code>
 274 <blockquote>
 275 <b>Returns:</b> <code>x.get()</code>.
 276 </blockquote>
 277
 278 <code>Type&amp; operator()(const reference_wrapper&lt;typename remove_const&lt;Type>::type>&amp; x)const;</code>
 279 <blockquote>
 280 <b>Returns:</b> <code>x.get()</code>.
 281 </blockquote>
 282
 283 <code>Type&amp; operator()(const reference_wrapper&lt;Type>&amp; x)const;</code>
 284 <blockquote>
 285 <b>Returns:</b> <code>x.get()</code>.
 286 </blockquote>
 287
 288
 289 <h2>
 290 <a name="member_synopsis">Header
 291 <a href="../../../../boost/multi_index/member.hpp">
 292 <code>"boost/multi_index/member.hpp"</code></a> synopsis</a></h2>
 293
 294 <blockquote><pre>
 295 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 296
 297 <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
 298
 299 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>&gt;</span>
 300 <span class=keyword>struct</span> <span class=identifier>member</span><span class=special>;</span>
 301
 302 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>OffsetOfMember</span><span class=special>&gt;</span>
 303 <span class=keyword>struct</span> <span class=identifier>member_offset</span><span class=special>;</span> <span class=comment><b>// deprecated</b></span>
 304
 305 <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span> <b>implementation defined</b>
 306
 307 <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
 308
 309 <span class=special>}</span> <span class=comment>// namespace boost</span>
 310 </pre></blockquote>
 311
 312 <h3><a name="member">Class template <code>member</code></a></h3>
 313
 314 <p>
 315 <code>member</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 316 aimed at accessing a given member of a class.
 317 </p>
 318
 319 <blockquote><pre>
 320 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>&gt;</span>
 321 <span class=keyword>struct</span> <span class=identifier>member</span>
 322 <span class=special>{</span>
 323   <span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span>
 324
 325   <span class=comment>// only provided if const ChainedPtr&amp; is not convertible to const Class&amp;</span>
 326   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>&gt;</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 327
 328   <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 329   <span class=identifier>Type</span><span class=special>&amp;</span>       <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const</span>
 330   <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&amp;</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 331   <span class=identifier>Type</span><span class=special>&amp;</span>       <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=identifier>Class</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 332 <span class=special>};</span>
 333 </pre></blockquote>
 334
 335 <p>
 336 The <code>PtrToMember</code> template argument specifies the particular
 337 <code>Type Class::*</code> pointer to the member to be extracted.
 338 <code>member&lt;Class,Type,PtrToMember></code> is a model of:
 339 <ul>
 340   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 341     from <code>Class</code>,</li>
 342   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 343     from <code>reference_wrapper&lt;const Class></code>,</li>
 344   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 345     from <code>reference_wrapper&lt;Class></code>,</li>
 346   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 347     from any <a href="#chained_pointers">chained pointer</a>
 348     to <code>const Class</code>,</li>
 349   <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
 350     from any <a href="#chained_pointers">chained pointer</a>
 351     to <code>Class</code>.</li>
 352 </ul>
 353 </p>
 354
 355 <h4><code>member</code> members</h4>
 356
 357 <code>template&lt;typename ChainedPtr> Type&amp; operator()(const ChainedPtr&amp; x)const;</code>
 358
 359 <blockquote>
 360 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 361 type to <code>Type</code>.<br>
 362 <b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>.
 363 </blockquote>
 364
 365 <code>const Type&amp; operator()(const Class&amp; x)const;</code>
 366
 367 <blockquote>
 368 <b>Returns:</b> <code>x.*PtrToMember</code>.
 369 </blockquote>
 370
 371 <code>Type&amp; operator()(Class&amp; x)const;</code>
 372
 373 <blockquote>
 374 <b>Returns:</b> <code>x.*PtrToMember</code>.
 375 </blockquote>
 376
 377 <code>const Type&amp; operator()(const reference_wrapper&lt;const Class>&amp; x)const;</code>
 378
 379 <blockquote>
 380 <b>Returns:</b> <code>x.get().*PtrToMember</code>.
 381 </blockquote>
 382
 383 <code>Type&amp; operator()(const reference_wrapper&lt;Class>&amp; x)const;</code>
 384
 385 <blockquote>
 386 <b>Returns:</b> <code>x.get().*PtrToMember</code>.
 387 </blockquote>
 388
 389 <h3><a name="member_offset">Class template <code>member_offset</code></a></h3>
 390
 391 <p>
 392 <code>member_offset</code> was designed to overcome limitations of some legacy
 393 compilers and its use is currently deprecated. Refer to a
 394 <a href="http://www.boost.org/doc/libs/1_54_0/libs/multi_index/doc/reference/key_extraction.html#member_offset">former version</a>
 395 of Boost.MultiIndex for further information.
 396 </p>
 397
 398 <h3><a name="boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></h3>
 399
 400 <blockquote><pre>
 401 <span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span>
 402 </pre></blockquote>
 403
 404 <p>
 405 This macro was designed as a portability mechanism for legacy compilers where <code>member</code>
 406 could not be supported.
 407 As such it is no longer needed in modern environments, though some users might still prefer it
 408 to plain <code>member</code> because it provides a slightly more concise syntax.
 409 </p>
 410
 411 <h2>
 412 <a name="mem_fun_synopsis">Header
 413 <a href="../../../../boost/multi_index/mem_fun.hpp">
 414 <code>"boost/multi_index/mem_fun.hpp"</code></a> synopsis</a></h2>
 415
 416 <blockquote><pre>
 417 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 418
 419 <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
 420
 421 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>&gt;</span>
 422 <span class=keyword>struct</span> <span class=identifier>const_mem_fun</span><span class=special>;</span>
 423
 424 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()&gt;</span>
 425 <span class=keyword>struct</span> <span class=identifier>mem_fun</span><span class=special>;</span>
 426
 427 <span class=keyword>template</span><span class=special>&lt;</span>
 428   <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
 429   <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
 430 <span class=special>&gt;</span>
 431 <span class=keyword>struct</span> <span class=identifier>const_mem_fun_explicit</span><span class=special>;</span> <span class=comment><b>// deprecated</b></span>
 432
 433 <span class=keyword>template</span><span class=special>&lt;</span>
 434   <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
 435   <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
 436 <span class=special>&gt;</span>
 437 <span class=keyword>struct</span> <span class=identifier>mem_fun_explicit</span><span class=special>;</span>       <span class=comment><b>// deprecated</b></span>
 438
 439 <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span>
 440 <b>implementation defined</b>
 441 <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span>
 442 <b>implementation defined</b>
 443
 444 <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
 445
 446 <span class=special>}</span> <span class=comment>// namespace boost</span>
 447 </pre></blockquote>
 448
 449 <h3><a name="const_mem_fun">Class template <code>const_mem_fun</code></a></h3>
 450
 451 <p>
 452 <code>const_mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 453 returning as key the result of invoking a given constant member function of a class.
 454 </p>
 455
 456 <blockquote><pre>
 457 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>&gt;</span>
 458 <span class=keyword>struct</span> <span class=identifier>const_mem_fun</span>
 459 <span class=special>{</span>
 460   <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special>&lt;</span><span class=identifier>Type</span><span class=special>&gt;::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
 461
 462   <span class=comment>// only provided if const ChainedPtr&amp; is not convertible to const Class&amp;</span>
 463   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>&gt;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 464
 465   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 466   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 467   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=identifier>Class</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 468 <span class=special>};</span>
 469 </pre></blockquote>
 470
 471 <p>
 472 The <code>PtrToMemberFunction</code> template argument specifies the particular
 473 <code>Type (Class::*PtrToMemberFunction)()const</code> pointer to the the constant
 474 member function used in the extraction.
 475 <code>const_mem_fun&lt;Class,Type,PtrToMemberFunction></code> is a model of:
 476 <ul>
 477   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 478     from <code>Class</code>,</li>
 479   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 480     from <code>reference_wrapper&lt;const Class></code>,</li>
 481   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 482     from <code>reference_wrapper&lt;Class></code>,</li>
 483   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 484     from any <a href="#chained_pointers">chained pointer</a>
 485     to <code>const Class</code>,</li>
 486   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 487     from any <a href="#chained_pointers">chained pointer</a>
 488     to <code>Class</code>.</li>
 489 </ul>
 490 </p>
 491
 492 <h4><code>const_mem_fun</code> members</h4>
 493
 494 <code>template&lt;typename ChainedPtr> Type operator()(const ChainedPtr&amp; x)const;</code>
 495
 496 <blockquote>
 497 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 498 type to <code>Type</code>.<br>
 499 <b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the
 500 object chained-pointed to by <code>x</code>.
 501 </blockquote>
 502
 503 <code>Type operator()(const Class&amp; x)const;</code>
 504
 505 <blockquote>
 506 <b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>.
 507 </blockquote>
 508
 509 <code>Type operator()(const reference_wrapper&lt;const Class>&amp; x)const;</code>
 510
 511 <blockquote>
 512 <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
 513 </blockquote>
 514
 515 <code>Type operator()(const reference_wrapper&lt;Class>&amp; x)const;</code>
 516
 517 <blockquote>
 518 <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
 519 </blockquote>
 520
 521 <h3><a name="mem_fun">Class template <code>mem_fun</code></a></h3>
 522
 523 <p>
 524 <code>mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 525 returning as key the result of invoking a given member function of a class.
 526 </p>
 527
 528 <blockquote><pre>
 529 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()&gt;</span>
 530 <span class=keyword>struct</span> <span class=identifier>mem_fun</span>
 531 <span class=special>{</span>
 532   <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special>&lt;</span><span class=identifier>Type</span><span class=special>&gt;::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
 533
 534   <span class=comment>// only provided if ChainedPtr&amp; is not convertible to Class&amp;</span>
 535   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>&gt;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 536
 537   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 538   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=identifier>Class</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 539 <span class=special>};</span>
 540 </pre></blockquote>
 541
 542 <p>
 543 The <code>PtrToMemberFunction</code> template argument specifies the particular
 544 <code>Type (Class::*PtrToMemberFunction)()</code> pointer to the the member
 545 function used in the extraction.
 546 <code>mem_fun&lt;Class,Type,PtrToMemberFunction></code> is a model of:
 547 <ul>
 548   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 549     from <code>reference_wrapper&lt;Class></code>,</li>
 550   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 551     from any <a href="#chained_pointers">chained pointer</a>
 552     to <code>Class</code>.</li>
 553 </ul>
 554 </p>
 555
 556 <h4><code>mem_fun</code> members</h4>
 557
 558 <code>template&lt;typename ChainedPtr> Type operator()(const ChainedPtr&amp; x)const;</code>
 559
 560 <blockquote>
 561 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 562 type to <code>Type</code>.<br>
 563 <b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the
 564 object chained-pointed to by <code>x</code>.
 565 </blockquote>
 566
 567 <code>Type operator()(Class&amp; x)const;</code>
 568
 569 <blockquote>
 570 <b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>.
 571 </blockquote>
 572
 573 <code>Type operator()(const reference_wrapper&lt;Class>&amp; x)const;</code>
 574
 575 <blockquote>
 576 <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
 577 </blockquote>
 578
 579 <h3><a name="const_mem_fun_explicit">Class templates <code>const_mem_fun_explicit</code> and <code>mem_fun_explicit</code></a></h3>
 580
 581 <p>
 582 These extractors were provided as a workaround for MSVC++ 6.0 and are now deprecated.
 583 Refer to a
 584 <a href="http://www.boost.org/doc/libs/1_54_0/libs/multi_index/doc/reference/key_extraction.html#const_mem_fun_explicit">former version</a>
 585 of Boost.MultiIndex for further information.
 586 </p>
 587
 588 <h3><a name="boost_multi_index_const_mem_fun">Macros
 589 <code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code>
 590 and <code>BOOST_MULTI_INDEX_MEM_FUN</code></a></h3>
 591
 592 <blockquote><pre>
 593 <span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span>
 594 <span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span>
 595 </pre></blockquote>
 596
 597 <p>
 598 Portability macros for usage of <code>const_mem_fun</code> and <code>mem_fun</code>.
 599 Although no longer needed in modern compilers, some users might still decide to
 600 resort to them as they provide a slightly more concise syntax.
 601 </p>
 602
 603 <h2>
 604 <a name="global_fun_synopsis">Header
 605 <a href="../../../../boost/multi_index/global_fun.hpp">
 606 <code>"boost/multi_index/global_fun.hpp"</code></a> synopsis</a></h2>
 607
 608 <blockquote><pre>
 609 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 610
 611 <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
 612
 613 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(*</span><span class=identifier>PtrToFunction</span><span class=special>)(</span><span class=identifier>Value</span><span class=special>)&gt;</span>
 614 <span class=keyword>struct</span> <span class=identifier>global_fun</span><span class=special>;</span>
 615
 616 <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
 617
 618 <span class=special>}</span> <span class=comment>// namespace boost</span>
 619 </pre></blockquote>
 620
 621 <h3><a name="global_fun">Class template <code>global_fun</code></a></h3>
 622
 623 <p>
 624 <code>global_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 625 based on a given global or static member function accepting the base type as argument
 626 and returning the associated key.
 627 </p>
 628
 629 <blockquote><pre>
 630 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>class</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(*</span><span class=identifier>PtrToFunction</span><span class=special>)(</span><span class=identifier>Value</span><span class=special>)&gt;</span>
 631 <span class=keyword>struct</span> <span class=identifier>global_fun</span>
 632 <span class=special>{</span>
 633   <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special>&lt;</span><span class=identifier>Type</span><span class=special>&gt;::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
 634
 635   <span class=comment>// Only provided under the following circumstances:
 636   //   - If Value is a reference to a constant type, only provided
 637   //     when const ChainedPtr&amp; is not convertible to Value;
 638   //   - if Value is a reference to a non-const type, only provided
 639   //     when ChainedPtr&amp; is not convertible to Value;
 640   //   - else, only provided when const ChainedPtr&amp; is not
 641   //     convertible to const Value&amp;.</span>
 642   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 643
 644   <span class=comment>// only provided if Value is a reference type</span>
 645   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Value</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 646
 647   <span class=comment>// only provided if Value is not a reference type</span>
 648   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 649
 650   <span class=comment>// only provided if Value is not a reference type</span>
 651   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 652
 653   <span class=comment>// only provided if Value is a reference type</span>
 654   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span>
 655     <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span>
 656       <span class=identifier>remove_reference</span><span class=special>&lt;</span><span class=identifier>Value</span><span class=special>&gt;::</span><span class=identifier>type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 657
 658   <span class=comment>// only provided if Value is not a reference type or is
 659   // a reference to a constant type</span>
 660   <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span>
 661     <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span>
 662       <span class=keyword>typename</span> <span class=identifier>remove_const</span><span class=special>&lt;</span>
 663         <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special>&lt;</span><span class=identifier>Value</span><span class=special>&gt;::</span><span class=identifier>type</span><span class=special>&gt;::</span><span class=identifier>type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 664 <span class=special>};</span>
 665 </pre></blockquote>
 666
 667 <p>
 668 <code>PtrToFunction</code> specifies the particular function used to extract
 669 the key of type <code>Type</code> from some <code>BaseType</code>.
 670 <code>global_fun</code> supports the following function signatures:
 671 <ul>
 672   <li><code>Type f(BaseType)</code> (<code>Value</code> is <code>BaseType</code>),</li>
 673   <li><code>Type f(const BaseType&amp;)</code> (<code>Value</code> is <code>const BaseType&amp;</code>),</li>
 674   <li><code>Type f(BaseType&amp;)</code> (<code>Value</code> is <code>BaseType&amp;</code>).</li>
 675 </ul>
 676 <code>global_fun&lt;Type,Value,PtrToFunction&gt;</code> is a model of:
 677 <ul>
 678   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 679     from <code>reference_wrapper&lt;BaseType></code>,</li>
 680   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 681     from any <a href="#chained_pointers">chained pointer</a>
 682     to <code>BaseType</code>.</li>
 683 </ul>
 684 When <code>Value</code> is <code>BaseType</code> or
 685 <code>const BaseType&amp;</code>,
 686 <code>global_fun&lt;Type,Value,PtrToFunction&gt;</code> is also a model of:
 687 <ul>
 688   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 689     from <code>BaseType</code>,</li>
 690   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 691     from <code>reference_wrapper&lt;const BaseType></code>,</li>
 692   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 693     from any <a href="#chained_pointers">chained pointer</a>
 694     to <code>const BaseType</code>.</li>
 695 </ul>
 696 </p>
 697
 698 <h4><code>global_fun</code> members</h4>
 699
 700 <code>template&lt;typename ChainedPtr> Type operator()(const ChainedPtr&amp; x)const;</code>
 701
 702 <blockquote>
 703 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 704 type to <code>Value</code>.<br>
 705 <b>Returns:</b> <code>PtrToFunction)(y)</code>, where <code>y</code> is the
 706 object chained-pointed to by <code>x</code>.
 707 </blockquote>
 708
 709 <code>Type operator()(Value x)const;</code>
 710
 711 <blockquote>
 712 <b>Returns:</b> <code>PtrToFunction(x)</code>.
 713 </blockquote>
 714
 715 <code>Type operator()(const Value&amp; x)const;</code>
 716
 717 <blockquote>
 718 <b>Returns:</b> <code>PtrToFunction(x)</code>.
 719 </blockquote>
 720
 721 <code>Type operator()(const reference_wrapper&lt;const Value&gt;&amp; x)const;</code>
 722
 723 <blockquote>
 724 <b>Returns:</b> <code>PtrToFunction(x.get())</code>.
 725 </blockquote>
 726
 727 <code>
 728 Type operator()(<br>
 729 &nbsp;&nbsp;const reference_wrapper&lt;remove_reference&lt;Value&gt;::type&gt;&amp; x)const;</code>
 730
 731 <blockquote>
 732 <b>Returns:</b> <code>PtrToFunction(x.get())</code>.
 733 </blockquote>
 734
 735 <code>Type operator()(<br>
 736 &nbsp;&nbsp;const reference_wrapper&lt;<br>
 737 &nbsp;&nbsp;&nbsp;&nbsp;typename remove_const&lt;<br>
 738 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;typename remove_reference&lt;Value&gt;::type&gt;::type&gt;&amp; x)const;</code>
 739
 740 <blockquote>
 741 <b>Returns:</b> <code>PtrToFunction(x.get())</code>.
 742 </blockquote>
 743
 744 <h2>
 745 <a name="composite_key_synopsis">Header
 746 <a href="../../../../boost/multi_index/composite_key.hpp">
 747 <code>"boost/multi_index/composite_key.hpp"</code></a> synopsis</a></h2>
 748
 749 <blockquote><pre>
 750 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 751
 752 <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
 753
 754 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>&gt;</span>
 755 <span class=keyword>struct</span> <span class=identifier>composite_key</span><span class=special>;</span>
 756
 757 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 758 <span class=keyword>struct</span> <span class=identifier>composite_key_result</span><span class=special>;</span>
 759
 760 <span class=comment>// comparison operators for composite_key_result:</span>
 761
 762 <span class=comment>// <b>OP</b> is any of ==,&lt;,!=,&gt;,&gt;=,&lt;=</span>
 763
 764 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
 765 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 766   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 767   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 768
 769 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
 770 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 771   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 772   <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 773
 774 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
 775 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 776   <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 777   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 778
 779 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
 780 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 781   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 782   <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 783
 784 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 785 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 786   <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 787   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 788
 789 <span class=comment>// equality functors:</span>
 790
 791 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Pred0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Predn</span><span class=special>&gt;</span>
 792 <span class=keyword>struct</span> <span class=identifier>composite_key_equal_to</span><span class=special>;</span>
 793
 794 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>&gt;</span>
 795 <span class=keyword>struct</span> <span class=identifier>composite_key_result_equal_to</span><span class=special>;</span> <span class=comment><b>// deprecated</b></span>
 796
 797 <span class=comment>// comparison functors:</span>
 798
 799 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>&gt;</span>
 800 <span class=keyword>struct</span> <span class=identifier>composite_key_compare</span><span class=special>;</span>
 801
 802 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>&gt;</span>
 803 <span class=keyword>struct</span> <span class=identifier>composite_key_result_less</span><span class=special>;</span>     <span class=comment><b>// deprecated</b></span>
 804
 805 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>&gt;</span>
 806 <span class=keyword>struct</span> <span class=identifier>composite_key_result_greater</span><span class=special>;</span>  <span class=comment><b>// deprecated</b></span>
 807
 808 <span class=comment>// hash functors:</span>
 809
 810 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Hash0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Hashn</span><span class=special>&gt;</span>
 811 <span class=keyword>struct</span> <span class=identifier>composite_key_hash</span><span class=special>;</span>
 812
 813 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>&gt;</span>
 814 <span class=keyword>struct</span> <span class=identifier>composite_key_result_hash</span><span class=special>;</span>     <span class=comment><b>// deprecated</b></span>
 815
 816 <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
 817
 818 <span class=special>}</span> <span class=comment>// namespace boost</span>
 819
 820 <span class=comment>// specializations of external functors for composite_key_result:</span>
 821
 822 <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
 823
 824 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 825 <span class=keyword>struct</span> <span class=identifier>equal_to</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;;</span>
 826
 827 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 828 <span class=keyword>struct</span> <span class=identifier>less</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;;</span>
 829
 830 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 831 <span class=keyword>struct</span> <span class=identifier>greater</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;;</span>
 832
 833 <span class=special>}</span> <span class=comment>// namespace std</span>
 834
 835 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
 836
 837 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 838 <span class=keyword>struct</span> <span class=identifier>hash</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;;</span>
 839
 840 <span class=special>}</span> <span class=comment>// namespace boost</span>
 841 </pre></blockquote>
 842
 843 <h3><a name="composite_key">Class template <code>composite_key</code></a></h3>
 844
 845 <p>
 846 <code>composite_key</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
 847 returning the combined value of several key extractors whose type is specified
 848 at compile time. The returned object is of type
 849 <a href="#composite_key_result">
 850 <code>composite_key_result</code></a><code>&lt;composite_key></code>.
 851 </p>
 852
 853 <blockquote><pre>
 854 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>&gt;</span>
 855 <span class=keyword>struct</span> <span class=identifier>composite_key</span>
 856 <span class=special>{</span>
 857   <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=identifier>KeyFromValuen</span><span class=special>&gt;</span> <span class=identifier>key_extractor_tuple</span><span class=special>;</span>
 858   <span class=keyword>typedef</span> <span class=identifier>Value</span>                                         <span class=identifier>value_type</span><span class=special>;</span>
 859   <span class=keyword>typedef</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>composite_key</span><span class=special>&gt;</span>           <span class=identifier>result_type</span><span class=special>;</span>
 860
 861   <span class=identifier>composite_key</span><span class=special>(</span>
 862     <span class=keyword>const</span> <span class=identifier>KeyFromValue0</span><span class=special>&amp;</span> <span class=identifier>k0</span><span class=special>=</span><span class=identifier>KeyFromValue0</span><span class=special>(),</span>
 863     <span class=special>...</span>
 864     <span class=keyword>const</span> <span class=identifier>KeyFromValuen</span><span class=special>&amp;</span> <span class=identifier>kn</span><span class=special>=</span><span class=identifier>KeyFromValuen</span><span class=special>());</span>
 865
 866   <span class=identifier>composite_key</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>);</span>
 867
 868   <span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&amp;</span> <span class=identifier>key_extractors</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
 869   <span class=identifier>key_extractor_tuple</span><span class=special>&amp;</span>       <span class=identifier>key_extractors</span><span class=special>()</span>
 870
 871   <span class=comment>// only provided if const ChainedPtr&amp; is not convertible to const value_type&amp;</span>
 872   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>&gt;</span>
 873   <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 874
 875   <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 876   <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 877   <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special>&lt;</span><span class=identifier>value_type</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
 878 <span class=special>};</span>
 879 </pre></blockquote>
 880
 881 <p>
 882 <code>KeyFromValue0</code>, ... , <code>KeyFromValuen</code> are the types of
 883 the key extractors combined into the composite key. Each of these types
 884 must be a <a href="#key_extractors"><code>Key Extractor</code></a> from
 885 <code>Value</code>. At least a key extractor must be provided. The maximum
 886 number of key extractors of a <code>composite_key</code> instantiation is
 887 implementation defined. <code>composite_key</code> internally stores an
 888 object of every constituent key extractor type.
 889 <code>composite_key&lt;Value,KeyFromValue0,...,KeyFromValuen></code> is a model
 890 of:
 891 <ul>
 892   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 893     from <code>Value</code>,</li>
 894   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 895     from <code>reference_wrapper&lt;const Value></code>,</li>
 896   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 897     from <code>reference_wrapper&lt;Value></code>,</li>
 898   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 899     from any <a href="#chained_pointers">chained pointer</a>
 900     to <code>const Value</code>,</li>
 901   <li><a href="#key_extractors"><code>Key Extractor</code></a>
 902     from any <a href="#chained_pointers">chained pointer</a>
 903     to <code>Value</code>.</li>
 904 </ul>
 905 </p>
 906
 907 <h4><code>composite_key</code> members</h4>
 908
 909 <code>composite_key(<br>
 910 &nbsp;&nbsp;const KeyFromValue0&amp; k0=KeyFromValue0(),<br>
 911 &nbsp;&nbsp;...<br>
 912 &nbsp;&nbsp;const KeyFromValuen&amp; kn=KeyFromValuen());
 913 </code>
 914
 915 <blockquote>
 916 <b>Effects:</b> Constructs a <code>composite_key</code> that stores
 917 copies of the key extractor objects supplied.
 918 </blockquote>
 919
 920 <code>composite_key(const key_extractor_tuple&amp; x);</code>
 921
 922 <blockquote>
 923 <b>Effects:</b> Constructs a <code>composite_key</code> that stores
 924 copies of the key extractor objects supplied in <code>x</code>.
 925 </blockquote>
 926
 927 <code>const key_extractor_tuple&amp; key_extractors()const;</code>
 928
 929 <blockquote>
 930 <b>Returns:</b> a constant reference to a tuple holding the
 931 key extractors internally stored by the <code>composite_key</code>.
 932 </blockquote>
 933
 934 <code>key_extractor_tuple&amp; key_extractors();</code>
 935
 936 <blockquote>
 937 <b>Returns:</b> a reference to a tuple holding the
 938 key extractors internally stored by the <code>composite_key</code>.
 939 </blockquote>
 940
 941 <code>template&lt;typename ChainedPtr><br>
 942 result_type operator()(const ChainedPtr&amp; x)const;</code>
 943
 944 <blockquote>
 945 <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
 946 type to <code>result_type</code>.<br>
 947 <b>Returns:</b> a <code>result_type</code> object dependent on
 948 <code>*this</code> and <code>y</code>, where <code>y</code> is the
 949 object chained-pointed to by <code>x</code>.
 950 </blockquote>
 951
 952 <code>result_type operator()(const value_type&amp; x)const;</code>
 953
 954 <blockquote>
 955 <b>Returns:</b> a <code>result_type</code> object dependent on
 956 <code>*this</code> and <code>x</code>.
 957 </blockquote>
 958
 959 <code>result_type operator()(const reference_wrapper&lt;const value_type>&amp; x)const;</code>
 960
 961 <blockquote>
 962 <b>Returns:</b> a <code>result_type</code> object dependent on
 963 <code>*this</code> and <code>x.get()</code>.
 964 </blockquote>
 965
 966 <code>result_type operator()(const reference_wrapper&lt;value_type>&amp; x)const;</code>
 967
 968 <blockquote>
 969 <b>Returns:</b> a <code>result_type</code> object dependent on
 970 <code>*this</code> and <code>x.get()</code>.
 971 </blockquote>
 972
 973 <h3><a name="composite_key_result">Class template
 974 <code>composite_key_result</code></a></h3>
 975
 976 <p>
 977 This is an opaque type returned by <code>composite_key</code>
 978 instantiations as their extracted key.
 979 </p>
 980
 981 <blockquote><pre>
 982 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
 983 <span class=keyword>struct</span> <span class=identifier>composite_key_result</span>
 984 <span class=special>{</span>
 985   <b>no public interface available</b>
 986 <span class=special>};</span>
 987
 988 <span class=comment>// comparison:</span>
 989
 990 <span class=comment>// <b>OP</b> is any of ==,&lt;,!=,&gt;,&gt;=,&lt;=</span>
 991
 992 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
 993 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 994   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
 995   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
 996
 997 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
 998 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
 999   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1000   <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
1001
1002 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1003 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
1004   <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1005   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
1006
1007 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1008 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
1009   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1010   <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
1011
1012 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1013 <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
1014   <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1015   <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>);</span>
1016 </pre></blockquote>
1017
1018 <code>CompositeKey</code> is the <code>composite_key</code> instantiation to
1019 which the <code>composite_key_result</code> type is associated. Objects of type
1020 <code>composite_key_result</code> returned by a composite key must be always treated
1021 as <i>temporary</i>, i.e. they should not be stored or copied.
1022 <code>composite_key_result</code> is <i>not</i> guaranteed to be
1023 <code>DefaultConstructible</code> or <code>CopyAssignable</code>.
1024 Every object of type <code>composite_key_result&lt;CompositeKey></code> is
1025 internally associated to the <code>CompositeKey</code> from which it is returned
1026 and the object of type <code>CompositeKey::value_type</code> to which the
1027 composite key was applied.
1028 </p>
1029
1030 <h4><a name="ckey_result_notation">Notation</a></h4>
1031
1032 <p>
1033 Given an <code>x</code> of type <code>composite_key_result&lt;CompositeKey></code>,
1034 we use the following notation:
1035 <ul>
1036   <li><code>ck(x)</code> is the <code>CompositeKey</code> object associated to
1037     <code>x</code>,</li>
1038   <li><code>v(x)</code> is the object of type <code>CompositeKey::value_type</code>
1039     associated to <code>x</code>,</li>
1040   <li><code>k<sub>i</sub>(x) = ck(x).key_extractors().get&lt;i>()</code>,
1041     that is, is the <code>i</code>-th key extractor of <code>ck(x)</code>,</li>
1042   <li><code>x<sub>i</sub> = k<sub>i</sub>(x)(v(x))</code>, that is, the
1043     key extracted from <code>v(x)</code> by the <code>i</code>-th key extractor,</li>
1044   <li><code>length(x)</code> is the number of key extractors of <code>ck(x)</code>.</li>
1045 </ul>
1046 Also, if <code>y</code> is an <code>std::tuple</code> or <code>boost::tuple</code> of values, we define:
1047 <ul>
1048   <li><code>y<sub>i</sub>=get&lt;i>(y)</code>,</li>
1049   <li><code>length(y)</code> is the number of elements of <code>y</code>.</li>
1050 </ul>
1051 </p>
1052
1053 <h4>Comparison operators</h4>
1054
1055 <code>template&lt;typename CompositeKey1,typename CompositeKey2><br>
1056 bool operator==(<br>
1057 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey1>&amp; x,<br>
1058 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey2>&amp; y);<br>
1059 template&lt;typename CompositeKey,typename... Values><br>
1060 bool operator==(<br>
1061 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1062 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; y);<br>
1063 template&lt;typename CompositeKey,typename... Values><br>
1064 bool operator==(<br>
1065 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x,<br>
1066 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);<br>
1067 template&lt;typename CompositeKey,typename Value0,...,typename Valuen><br>
1068 bool operator==(<br>
1069 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1070 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; y);<br>
1071 template&lt;typename Value0,...,typename Valuen,typename CompositeKey><br>
1072 bool operator==(<br>
1073 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x,<br>
1074 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);
1075 </code>
1076
1077 <blockquote>
1078 <b>Requires:</b> <code>length(x)==length(y)</code>. The expression
1079 <code>x<sub>i</sub>==y<sub>i</sub></code> is valid for all <code>i</code>
1080 in <code>[0,length(x))</code>.<br>
1081 <b>Returns:</b> <code>true</code> if and only if
1082 <blockquote>
1083 <code>x<sub>i</sub>==y<sub>i</sub></code> for all <code>i</code>
1084 in <code>[0,length(x))</code>.
1085 </blockquote>
1086 <b>Complexity:</b> No more key extraction operations and comparisons
1087 are performed than those necessary for the evaluation of the expression above,
1088 starting at <code>i==0</code>. The evaluation is short-circuited as soon as
1089 the result is determined to be <code>false</code>.
1090 </blockquote>
1091
1092 <code>template&lt;typename CompositeKey1,typename CompositeKey2><br>
1093 bool operator<(<br>
1094 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey1>&amp; x,<br>
1095 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey2>&amp; y);<br>
1096 template&lt;typename CompositeKey,typename... Values><br>
1097 bool operator<(<br>
1098 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1099 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; y);<br>
1100 template&lt;typename CompositeKey,typename... Values><br>
1101 bool operator<(<br>
1102 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x,<br>
1103 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);<br>
1104 template&lt;typename CompositeKey,typename Value0,...,typename Valuen><br>
1105 bool operator<(<br>
1106 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1107 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; y);<br>
1108 template&lt;typename Value0,...,typename Valuen,typename CompositeKey><br>
1109 bool operator<(<br>
1110 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x,<br>
1111 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);
1112 </code>
1113
1114 <blockquote>
1115 <b>Requires:</b> The expressions
1116 <code>x<sub>i</sub>&lt;y<sub>i</sub></code> and
1117 <code>y<sub>i</sub>&lt;x<sub>i</sub></code> are valid for all <code>i</code>
1118 in <code>[0,min(length(x),length(y)))</code>.<br>
1119 <b>Returns:</b> <code>true</code> if and only if there exists some
1120 <code>j</code> in the range <code>[0,min(length(x),length(y)))</code>
1121 such that
1122 <blockquote>
1123 <code>!(x<sub>i</sub>&lt;y<sub>i</sub>) &amp;&amp; !(y<sub>i</sub>&lt;x<sub>i</sub>)</code>
1124 for all <code>i</code> in <code>[0,j)</code>,<br>
1125 <code>&nbsp;&nbsp;x<sub>j</sub>&lt;y<sub>j</sub></code>.
1126 </blockquote>
1127 <b>Complexity:</b> No more key extraction operations and comparisons
1128 are performed than those necessary for the evaluation of the expression above,
1129 starting at <code>i==0</code>. The evaluation is short-circuited as soon as
1130 the result is determined to be <code>false</code>.
1131 </blockquote>
1132
1133 <code>template&lt;typename CompositeKey1,typename CompositeKey2><br>
1134 bool operator <b><i>OP</i></b>(<br>
1135 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey1>&amp; x,<br>
1136 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey2>&amp; y);<br>
1137 template&lt;typename CompositeKey,typename... Values><br>
1138 bool operator <b><i>OP</i></b>(<br>
1139 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1140 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; y);<br>
1141 template&lt;typename CompositeKey,typename... Values><br>
1142 bool operator <b><i>OP</i></b>(<br>
1143 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x,<br>
1144 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);<br>
1145 template&lt;typename CompositeKey,typename Value0,...,typename Valuen><br>
1146 bool operator <b><i>OP</i></b>(<br>
1147 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1148 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; y);<br>
1149 template&lt;typename Value0,...,typename Valuen,typename CompositeKey><br>
1150 bool operator <b><i>OP</i></b>(<br>
1151 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x,<br>
1152 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y);
1153 </code>
1154
1155 <p>
1156 (<code><b><i>OP</i></b></code> is any of <code>!=</code>, <code>></code>,
1157 <code>>=</code>, <code>&lt;=</code>.)
1158 </p>
1159
1160 <blockquote>
1161 <b>Requires:</b> The expressions given below are valid (for the particular
1162 <code><b><i>OP</i></b></code> considered.)<br>
1163 <b>Returns:</b> <code>true</code> if and only if
1164 <blockquote>
1165 <code>!(x==y)</code> (<code><b><i>OP</i></b></code> is <code>!=</code>),<br>
1166 <code>&nbsp;&nbsp;y&lt;&nbsp;x&nbsp;</code> (<code><b><i>OP</i></b></code> is <code>>&nbsp;</code>),<br>
1167 <code>!(x&lt;&nbsp;y)</code> (<code><b><i>OP</i></b></code> is <code>>=</code>),<br>
1168 <code>!(y&lt;&nbsp;x)</code> (<code><b><i>OP</i></b></code> is <code>&lt;=</code>).
1169 </blockquote>
1170 </blockquote>
1171
1172 <h3><a name="ckey_result_equality">Equality</a></h3>
1173
1174 <h4><a name="composite_key_equal_to">Class template
1175 <code>composite_key_equal_to</code></a></h4>
1176
1177 <p>
1178 <code>composite_key_equal_to</code> tests for equality between
1179 <code>composite_key_result</code> instantiations and between
1180 these and tuples of values, using an internally stored
1181 collection of elementary equality predicates.
1182 </p>
1183
1184 <blockquote><pre>
1185 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Pred0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Predn</span><span class=special>&gt;</span>
1186 <span class=keyword>struct</span> <span class=identifier>composite_key_equal_to</span>
1187 <span class=special>{</span>
1188   <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Pred0</span><span class=special>,...,</span><span class=identifier>Predn</span><span class=special>&gt;</span> <span class=identifier>key_eq_tuple</span><span class=special>;</span>
1189
1190   <span class=identifier>composite_key_equal_to</span><span class=special>(</span>
1191     <span class=keyword>const</span> <span class=identifier>Pred0</span><span class=special>&amp;</span> <span class=identifier>p0</span><span class=special>=</span><span class=identifier>Pred0</span><span class=special>(),</span>
1192     <span class=special>...</span>
1193     <span class=keyword>const</span> <span class=identifier>Predn</span><span class=special>&amp;</span> <span class=identifier>pn</span><span class=special>=</span><span class=identifier>Predn</span><span class=special>());</span>
1194
1195   <span class=identifier>composite_key_equal_to</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_eq_tuple</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>);</span>
1196
1197   <span class=keyword>const</span> <span class=identifier>key_eq_tuple</span><span class=special>&amp;</span> <span class=identifier>key_eqs</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
1198   <span class=identifier>key_eq_tuple</span><span class=special>&amp;</span>       <span class=identifier>key_eqs</span><span class=special>()</span><span class=special>;</span>
1199
1200   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
1201   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1202     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1203     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1204
1205   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1206   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1207     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1208     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1209
1210   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1211   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1212     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1213     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1214
1215   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1216   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1217     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1218     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1219
1220   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1221   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1222     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1223     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1224 <span class=special>};</span>
1225 </pre></blockquote>
1226
1227 <p>
1228 <code>Pred0</code>, ... , <code>Predn</code> are the types of the equality
1229 binary predicates stored by <code>composite_key_equal_to</code>. Each of these predicates
1230 must be <code>CopyConstructible</code> and <code>CopyAssignable</code>. At least an
1231 equality predicate must be provided. The maximum number of equality predicates of
1232 a <code>composite_key_equal_to</code> instantiation is implementation defined.
1233 <code>composite_key_equal_to</code> is
1234 <code>CopyConstructible</code> and <code>CopyAssignable</code>.
1235 It is also <code>DefaultConstructible</code>
1236 if each <code>Predi</code> is <code>DefaultConstructible</code> in its turn.
1237 </p>
1238
1239 <p>
1240 Note that formally it is not required that the <code>Predi</code> types
1241 behave as equality predicates in any definite way. However, the
1242 semantics of <code>composite_key_equal_to</code> is well defined if this
1243 is the case, as explained in the section on the
1244 <a href="#ckey_result_semantics">semantics of <code>composite_key_result</code></a>.
1245 </p>
1246
1247 <h4>Notation</h4>
1248
1249 <p>
1250 In what follows we use the same <a href="#ckey_result_notation">notation</a>
1251 introduced for <code>composite_key_result</code>.
1252
1253 <h4><code>composite_key_equal_to</code> members</h4>
1254
1255 <code>composite_key_equal_to(<br>
1256 &nbsp;&nbsp;const Pred0&amp; p0=Pred0(),<br>
1257 &nbsp;&nbsp;...<br>
1258 &nbsp;&nbsp;const Predn&amp; pn=Predn());
1259 </code>
1260
1261 <blockquote>
1262 <b>Effects:</b> Constructs a <code>composite_key_equal_to</code> that stores
1263 copies of the equality predicates supplied.
1264 </blockquote>
1265
1266 <code>composite_key_equal_to(const key_eq_tuple&amp; x);</code>
1267
1268 <blockquote>
1269 <b>Effects:</b> Constructs a <code>composite_key_equal_to</code> that stores
1270 copies of the equality predicate objects supplied in <code>x</code>.
1271 </blockquote>
1272
1273 <code>const key_eq_tuple&amp; key_eqs()const;</code>
1274
1275 <blockquote>
1276 <b>Returns:</b> a constant reference to a tuple holding the
1277 equality predicate objects internally stored by the
1278 <code>composite_key_equal_to</code>.
1279 </blockquote>
1280
1281 <code>key_eq_tuple&amp; key_eqs();</code>
1282
1283 <blockquote>
1284 <b>Returns:</b> a reference to a tuple holding the
1285 equality predicate objects internally stored by the
1286 <code>composite_key_equal_to</code>.
1287 </blockquote>
1288
1289 <code>
1290 template&lt;typename CompositeKey1,typename CompositeKey2><br>
1291 bool operator()(<br>
1292 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey1> &amp; x,<br>
1293 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey2> &amp; y)const;<br>
1294 template&lt;typename CompositeKey,typename Values...><br>
1295 bool operator()(<br>
1296 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1297 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; y)const;<br>
1298 template&lt;typename CompositeKey,typename Values...><br>
1299 bool operator()(<br>
1300 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x,<br>
1301 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y)const;<br>
1302 template&lt;typename CompositeKey,typename Value0,...,typename Valuen><br>
1303 bool operator()(<br>
1304 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1305 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; y)const;<br>
1306 template&lt;typename Value0,...,typename Valuen,typename CompositeKey><br>
1307 bool operator()(<br>
1308 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x,<br>
1309 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y)const;<br>
1310 </code>
1311
1312 <blockquote>
1313 <b>Requires:</b> <code>length(x)==length(y)</code>. The expressions
1314 <code>key_eqs().get&lt;i>()(x<sub>i</sub>,y<sub>i</sub>)</code> and
1315 <code>key_eqs().get&lt;i>()(y<sub>i</sub>,x<sub>i</sub>)</code>
1316 are valid for all <code>i</code> in <code>[0,length(x))</code>.<br>
1317 <b>Returns:</b> <code>true</code> if and only
1318 <blockquote>
1319 <code>key_eqs().get&lt;i>()(x<sub>i</sub>,y<sub>i</sub>)</code>
1320 for all <code>i</code> in <code>[0,length(x))</code>.<br>
1321 </blockquote>
1322 <b>Complexity:</b> No more key extraction operations and comparisons
1323 are performed than those necessary for the evaluation of the expression above,
1324 starting at <code>i==0</code>. The evaluation is short-circuited as soon as
1325 the result is determined to be <code>false</code>.
1326 </blockquote>
1327
1328 <h4><a name="composite_key_result_equal_to">Class template
1329 <code>composite_key_result_equal_to</code></a></h4>
1330
1331 <p>
1332 Deprecated. Use <code>std::equal_to&lt;CompositeKeyResult&gt;</code> instead.
1333 </p>
1334
1335 <h4><a name="equal_to_composite_key_result">Specialization of
1336 <code>std::equal_to</code> for <code>composite_key</code> results</a></h4>
1337
1338 <p>
1339 <code>std::equal_to&lt;CompositeKeyResult></code>, with <code>CompositeKeyResult</code>
1340 an instantiation of <code>composite_key_result</code>,
1341 behaves as a particularization of
1342 <code>composite_key_equal_to</code> where all the comparison predicates supplied
1343 are instantiations of <code>std::equal_to</code>.
1344 </p>
1345
1346 <blockquote><pre>
1347 <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
1348
1349 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1350 <span class=keyword>struct</span> <span class=identifier>equal_to</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;</span>
1351 <span class=special>{</span>
1352   <span class=keyword>typedef</span>
1353     <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span>
1354       <span class=identifier>CompositeKey</span><span class=special>&gt;</span>                           <span class=identifier>first_argument_type</span><span class=special>;</span>
1355   <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span>                 <span class=identifier>second_argument_type</span><span class=special>;</span>
1356   <span class=keyword>typedef</span> <span class=keyword>bool</span>                                <span class=identifier>result_type</span><span class=special>;</span>
1357
1358   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
1359   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1360     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1361     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1362
1363   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1364   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1365     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1366     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1367
1368   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1369   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1370     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1371     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1372
1373   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1374   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1375     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1376     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1377
1378   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1379   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1380     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1381     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1382 <span class=special>};</span>
1383
1384 <span class=special>}</span> <span class=comment>// namespace std</span>
1385 </pre></blockquote>
1386
1387 <p>
1388 <code>CompositeKeyResult</code> must be an instantiation of
1389 <code>composite_key_result</code> for some type
1390 <code>composite_key&lt;KeyFromValue0,...,KeyFromValuen></code>.
1391 <code>std::equal:to&lt;CompositeKeyResult>::operator()</code> is
1392 then equivalent to
1393 <code>composite_key_equal_to&lt;Pred0,...,Predn>::operator()</code>, taking
1394 <blockquote>
1395 <code>Predi = std::equal_to&lt;KeyFromValuei::result_type></code> for all
1396 <code>i = 0,...,n</code>.
1397 </blockquote>
1398 </p>
1399
1400 <p>
1401 In addition to the requirements on <code>Predi</code> imposed by
1402 <code>composite_key_equal_to</code>, each of these types must be
1403 <code>DefaultConstructible</code>. <code>std::equal_to&lt;CompositeKeyResult></code>
1404 is <code>DefaultConstructible</code>, <code>CopyConstructible</code> and
1405 <code>CopyAssignable</code>.
1406 </p>
1407
1408 <h3><a name="ckey_result_comparison">Comparison</a></h3>
1409
1410 <h4><a name="composite_key_compare">Class template
1411 <code>composite_key_compare</code></a></h4>
1412
1413 <p>
1414 <code>composite_key_compare</code> compares <code>composite_key_result</code>
1415 instantiations between them and with tuples of values using an internally stored
1416 collection of elementary comparison predicates.
1417 </p>
1418
1419 <blockquote><pre>
1420 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>&gt;</span>
1421 <span class=keyword>struct</span> <span class=identifier>composite_key_compare</span>
1422 <span class=special>{</span>
1423   <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Compare0</span><span class=special>,...,</span><span class=identifier>Comparen</span><span class=special>&gt;</span> <span class=identifier>key_comp_tuple</span><span class=special>;</span>
1424
1425   <span class=identifier>composite_key_compare</span><span class=special>(</span>
1426     <span class=keyword>const</span> <span class=identifier>Compare0</span><span class=special>&amp;</span> <span class=identifier>c0</span><span class=special>=</span><span class=identifier>Compare0</span><span class=special>(),</span>
1427     <span class=special>...</span>
1428     <span class=keyword>const</span> <span class=identifier>Comparen</span><span class=special>&amp;</span> <span class=identifier>cn</span><span class=special>=</span><span class=identifier>Comparen</span><span class=special>());</span>
1429
1430   <span class=identifier>composite_key_compare</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>);</span>
1431
1432   <span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&amp;</span> <span class=identifier>key_comps</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
1433   <span class=identifier>key_comp_tuple</span><span class=special>&amp;</span>       <span class=identifier>key_comps</span><span class=special>()</span><span class=special>;</span>
1434
1435   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
1436   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1437     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1438     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1439
1440   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1441   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1442     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1443     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1444
1445   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1446   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1447     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1448     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1449
1450   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1451   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1452     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1453     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1454
1455   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1456   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1457     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1458     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1459
1460   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>&gt;</span>
1461   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1462     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1463
1464   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1465   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1466     <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1467 <span class=special>};</span>
1468 </pre></blockquote>
1469
1470 <p>
1471 <code>Compare0</code>, ... , <code>Comparen</code> are the types of the comparison
1472 binary predicates stored by <code>composite_key_compare</code>. Each of these predicates must be
1473 <code>CopyConstructible</code> and <code>CopyAssignable</code>. At least a
1474 comparison predicate must be provided. The maximum number of comparison predicates of
1475 a <code>composite_key_compare</code> instantiation is implementation defined.
1476 <code>composite_key_compare</code> is
1477 <code>CopyConstructible</code> and <code>CopyAssignable</code>.
1478 It is also
1479 <code>DefaultConstructible</code>
1480 if each <code>Comparei</code> is <code>DefaultConstructible</code> in its turn.
1481 </p>
1482
1483 <p>
1484 Note that formally it is not required that the <code>Comparei</code> types
1485 behave as comparison predicates in any definite way. However, the
1486 semantics of <code>composite_key_compare</code> is well defined if this
1487 is the case, as explained in the section on the
1488 <a href="#ckey_result_semantics">semantics of <code>composite_key_result</code></a>.
1489 </p>
1490
1491 <h4>Notation</h4>
1492
1493 <p>
1494 In what follows we use the same <a href="#ckey_result_notation">notation</a>
1495 introduced for <code>composite_key_result</code>.
1496
1497 <h4><code>composite_key_compare</code> members</h4>
1498
1499 <code>composite_key_compare(<br>
1500 &nbsp;&nbsp;const Compare0&amp; c0=Compare0(),<br>
1501 &nbsp;&nbsp;...<br>
1502 &nbsp;&nbsp;const Comparen&amp; cn=Comparen());
1503 </code>
1504
1505 <blockquote>
1506 <b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores
1507 copies of the comparison predicates supplied.
1508 </blockquote>
1509
1510 <code>composite_key_compare(const key_comp_tuple&amp; x);</code>
1511
1512 <blockquote>
1513 <b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores
1514 copies of the comparison predicate objects supplied in <code>x</code>.
1515 </blockquote>
1516
1517 <code>const key_comp_tuple&amp; key_comps()const;</code>
1518
1519 <blockquote>
1520 <b>Returns:</b> a constant reference to a tuple holding the
1521 comparison predicate objects internally stored by the
1522 <code>composite_key_compare</code>.
1523 </blockquote>
1524
1525 <code>key_comp_tuple&amp; key_comps();</code>
1526
1527 <blockquote>
1528 <b>Returns:</b> a reference to a tuple holding the
1529 comparison predicate objects internally stored by the
1530 <code>composite_key_compare</code>.
1531 </blockquote>
1532
1533 <code>
1534 template&lt;typename CompositeKey1,typename CompositeKey2><br>
1535 bool operator()(<br>
1536 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey1> &amp; x,<br>
1537 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey2> &amp; y)const;<br>
1538 template&lt;typename CompositeKey,typename... Values><br>
1539 bool operator()(<br>
1540 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1541 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; y)const;<br>
1542 template&lt;typename CompositeKey,typename... Values><br>
1543 bool operator()(<br>
1544 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x,<br>
1545 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y)const;<br>
1546 template&lt;typename CompositeKey,typename Value0,...,typename Valuen><br>
1547 bool operator()(<br>
1548 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x,<br>
1549 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; y)const;<br>
1550 template&lt;typename Value0,...,typename Valuen,typename CompositeKey><br>
1551 bool operator()(<br>
1552 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x,<br>
1553 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; y)const;<br>
1554 </code>
1555
1556 <blockquote>
1557 <b>Requires:</b> The expressions
1558 <code>key_comps().get&lt;i>()(x<sub>i</sub>,y<sub>i</sub>)</code> and
1559 <code>key_comps().get&lt;i>()(y<sub>i</sub>,x<sub>i</sub>)</code>
1560 are valid for all <code>i</code>
1561 in <code>[0,min(length(x),length(y)))</code>.<br>
1562 <b>Returns:</b> <code>true</code> if and only if there exists some
1563 <code>j</code> in the range <code>[0,min(length(x),length(y)))</code>
1564 such that
1565 <blockquote>
1566 <code>!key_comps().get&lt;i>()(x<sub>i</sub>,y<sub>i</sub>) &amp;&amp; !key_comps().get&lt;i>()(y<sub>i</sub>,x<sub>i</sub>)</code>
1567 for all <code>i</code> in <code>[0,j)</code>,<br>
1568 <code>&nbsp;key_comps().get&lt;j>()(x<sub>j</sub>,y<sub>j</sub>)</code>.
1569 </blockquote>
1570 <b>Complexity:</b> No more key extraction operations and comparisons
1571 are performed than those necessary for the evaluation of the expression above,
1572 starting at <code>i==0</code>. The evaluation is short-circuited as soon as
1573 the result is determined to be <code>false</code>.
1574 </blockquote>
1575
1576 <code>
1577 template&lt;typename CompositeKey,typename Value&gt;<br>
1578 bool operator()(<br>
1579 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey&gt;&amp; x,const Value&amp; y)const;
1580 </code>
1581
1582 <blockquote>
1583 <b>Effects:</b>
1584 <blockquote><pre>
1585 <span class=keyword>return</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>x</span><span class=special>,</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>cref</span><span class=special>(</span><span class=identifier>y</span><span class=special>)));</span>
1586 </pre></blockquote><br>
1587 </blockquote>
1588
1589 <code>
1590 template&lt;typename Value,typename CompositeKey&gt;<br>
1591 bool operator()(<br>
1592 &nbsp;&nbsp;const Value&amp; x,const composite_key_result&lt;CompositeKey&gt;&amp; y)const;
1593 </code>
1594
1595 <blockquote>
1596 <b>Effects:</b>
1597 <blockquote><pre>
1598 <span class=keyword>return</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>cref</span><span class=special>(</span><span class=identifier>x</span><span class=special>)),</span><span class=identifier>y</span><span class=special>);</span>
1599 </pre></blockquote><br>
1600 </blockquote>
1601
1602 <h4><a name="composite_key_result_less">Class template
1603 <code>composite_key_result_less</code></a></h4>
1604
1605 <p>
1606 Deprecated. Use <code>std::less&lt;CompositeKeyResult&gt;</code> instead.
1607 </p>
1608
1609 <h4><a name="composite_key_result_greater">Class template
1610 <code>composite_key_result_greater</code></a></h4>
1611
1612 <p>
1613 Deprecated. Use <code>std::greater&lt;CompositeKeyResult&gt;</code> instead.
1614 </p>
1615
1616 <h4><a name="less_composite_key_result">Specialization of <code>std::less</code> for
1617 <code>composite_key</code> results</a></h4>
1618
1619 <p>
1620 <code>std::less&lt;CompositeKeyResult></code>, with <code>CompositeKeyResult</code>
1621 an instantiation of <code>composite_key_result</code>, behaves as a particularization of
1622 <code>composite_key_compare</code> where all the comparison predicates supplied are
1623 instantiations of <code>std::less</code>.
1624 </p>
1625
1626 <blockquote><pre>
1627 <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
1628
1629 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1630 <span class=keyword>struct</span> <span class=identifier>less</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;</span>
1631 <span class=special>{</span>
1632   <span class=keyword>typedef</span>
1633     <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span>
1634       <span class=identifier>CompositeKey</span><span class=special>&gt;</span>                           <span class=identifier>first_argument_type</span><span class=special>;</span>
1635   <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span>                 <span class=identifier>second_argument_type</span><span class=special>;</span>
1636   <span class=keyword>typedef</span> <span class=keyword>bool</span>                                <span class=identifier>result_type</span><span class=special>;</span>
1637
1638   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
1639   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1640     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1641     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1642
1643   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1644   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1645     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1646     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1647
1648   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1649   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1650     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1651     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1652
1653   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1654   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1655     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1656     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1657
1658   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1659   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1660     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1661     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1662
1663   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>&gt;</span>
1664   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1665     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1666     <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1667
1668   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1669   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1670     <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1671     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1672 <span class=special>};</span>
1673
1674 <span class=special>}</span> <span class=comment>// namespace std</span>
1675 </pre></blockquote>
1676
1677 <p>
1678 <code>CompositeKeyResult</code> must be an instantiation of
1679 <code>composite_key_result</code> for some type
1680 <code>composite_key&lt;KeyFromValue0,...,KeyFromValuen></code>.
1681 <code>std::less&lt;CompositeKeyResult>::operator()</code> is
1682 then equivalent to
1683 <code>composite_key_compare&lt;Compare0,...,Comparen>::operator()</code>, taking
1684 <blockquote>
1685 <code>Comparei = std::less&lt;KeyFromValuei::result_type></code> for all
1686 <code>i = 0,...,n</code>.
1687 </blockquote>
1688 </p>
1689
1690 <p>
1691 In addition to the requirements on <code>Comparei</code> imposed by
1692 <code>composite_key_compare</code>, each of these types must be
1693 <code>DefaultConstructible</code>. <code>std::less&lt;CompositeKeyResult></code>
1694 is <code>CopyConstructible</code>, <code>CopyConstructible</code>
1695 and <code>CopyAssignable</code>.
1696 </p>
1697
1698 <h4><a name="greater_composite_key_result">Specialization of <code>std::greater</code> for
1699 <code>composite_key</code> results</a></h4>
1700
1701 <p>
1702 <code>std::greater&lt;CompositeKeyResult></code>, with <code>CompositeKeyResult</code>
1703 an instantiation of <code>composite_key_result</code>, behaves as a particularization of
1704 <code>composite_key_compare</code> where all the comparison predicates supplied
1705 are instantiations of <code>std::greater</code>.
1706 </p>
1707
1708
1709 <blockquote><pre>
1710 <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
1711
1712 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1713 <span class=keyword>struct</span> <span class=identifier>greater</span><span class=special>&lt;</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;</span>
1714 <span class=special>{</span>
1715   <span class=keyword>typedef</span>
1716     <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span>
1717       <span class=identifier>CompositeKey</span><span class=special>&gt;</span>                           <span class=identifier>first_argument_type</span><span class=special>;</span>
1718   <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span>                 <span class=identifier>second_argument_type</span><span class=special>;</span>
1719   <span class=keyword>typedef</span> <span class=keyword>bool</span>                                <span class=identifier>result_type</span><span class=special>;</span>
1720
1721   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>&gt;</span>
1722   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1723     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey1</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1724     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey2</span><span class=special>&gt;</span> <span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1725
1726   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1727   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1728     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1729     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1730
1731   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1732   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1733     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1734     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1735
1736   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1737   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1738     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1739     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1740
1741   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1742   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1743     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1744     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1745
1746   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>&gt;</span>
1747   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1748     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1749     <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1750
1751   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1752   <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
1753     <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>,</span>
1754     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1755 <span class=special>};</span>
1756
1757 <span class=special>}</span> <span class=comment>// namespace std</span>
1758 </pre></blockquote>
1759
1760 <p>
1761 <code>CompositeKeyResult</code> must be an instantiation of
1762 <code>composite_key_result</code> for some type
1763 <code>composite_key&lt;KeyFromValue0,...,KeyFromValuen></code>.
1764 <code>std::greater&lt;CompositeKeyResult>::operator()</code> is
1765 then equivalent to
1766 <code>composite_key_compare&lt;Compare0,...,Comparen>::operator()</code>, taking
1767 <blockquote>
1768 <code>Comparei = std::greater&lt;KeyFromValuei::result_type></code> for all
1769 <code>i = 0,...,n</code>.
1770 </blockquote>
1771 </p>
1772
1773 <p>
1774 In addition to the requirements on <code>Comparei</code> imposed by
1775 <code>composite_key_compare</code>, each of these types must be
1776 <code>DefaultConstructible</code>. <code>std::greater&lt;CompositeKeyResult></code>
1777 is <code>CopyConstructible</code>, <code>CopyConstructible</code>
1778 and <code>CopyAssignable</code>.
1779 </p>
1780
1781 <h3><a name="ckey_result_hashing">Hashing</a></h3>
1782
1783 <h4><a name="composite_key_hash">Class template
1784 <code>composite_key_hash</code></a></h4>
1785
1786 <p>
1787 <code>composite_key_hash</code> produces hash values for <code>composite_key_result</code>
1788 instantiations based on a collection of elementary hash functors.
1789 </p>
1790
1791 <blockquote><pre>
1792 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Hash0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Hashn</span><span class=special>&gt;</span>
1793 <span class=keyword>struct</span> <span class=identifier>composite_key_hash</span>
1794 <span class=special>{</span>
1795   <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Hash0</span><span class=special>,...,</span><span class=identifier>Hashn</span><span class=special>&gt;</span> <span class=identifier>key_hasher_tuple</span><span class=special>;</span>
1796
1797   <span class=identifier>composite_key_hash</span><span class=special>(</span>
1798     <span class=keyword>const</span> <span class=identifier>Hash0</span><span class=special>&amp;</span> <span class=identifier>h0</span><span class=special>=</span><span class=identifier>Hash0</span><span class=special>(),</span>
1799     <span class=special>...</span>
1800     <span class=keyword>const</span> <span class=identifier>Hashn</span><span class=special>&amp;</span> <span class=identifier>hn</span><span class=special>=</span><span class=identifier>Hashn</span><span class=special>());</span>
1801
1802   <span class=identifier>composite_key_hash</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_hasher_tuple</span><span class=special>&amp;</span> <span class=identifier>x</span><span class=special>);</span>
1803
1804   <span class=keyword>const</span> <span class=identifier>key_hasher_tuple</span><span class=special>&amp;</span> <span class=identifier>key_hash_functions</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
1805   <span class=identifier>key_hasher_tuple</span><span class=special>&amp;</span>       <span class=identifier>key_hash_functions</span><span class=special>()</span><span class=special>;</span>
1806
1807   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1808   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1809     <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1810
1811   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1812   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1813     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1814
1815   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1816   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1817     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1818 <span class=special>};</span>
1819 </pre></blockquote>
1820
1821 <p>
1822 <code>Hash0</code>, ... , <code>Hashn</code> are the types of the hash unary function objects
1823 stored by <code>composite_key_hash</code>. Each of these objects
1824 must be <code>CopyConstructible</code> and <code>CopyAssignable</code>
1825 and return a value of type <code>std::size_t</code> in the range
1826 [0, <code>std::numeric_limits&lt;std::size_t&gt;::max())</code>).
1827 At least a hash functor must be provided. The maximum number of hash functors of
1828 a <code>composite_key_hash</code> instantiation is implementation defined.
1829 <code>composite_key_hash</code> is
1830 <code>CopyConstructible</code> and <code>CopyAssignable</code>.
1831 It is also <code>DefaultConstructible</code>
1832 if each <code>Hashi</code> is <code>DefaultConstructible</code> in its turn.
1833 </p>
1834
1835 <h4>Notation</h4>
1836
1837 <p>
1838 In what follows we use the same <a href="#ckey_result_notation">notation</a>
1839 introduced for <code>composite_key_result</code>.
1840
1841 <h4><code>composite_key_hash</code> members</h4>
1842
1843 <code>composite_key_hash(<br>
1844 &nbsp;&nbsp;const Hash0&amp; h0=Hash0(),<br>
1845 &nbsp;&nbsp;...<br>
1846 &nbsp;&nbsp;const Hashn&amp; hn=Hashn());
1847 </code>
1848
1849 <blockquote>
1850 <b>Effects:</b> Constructs a <code>composite_key_hash</code> that stores
1851 copies of the hash functors supplied.
1852 </blockquote>
1853
1854 <code>composite_key_hash(const key_hasher_tuple&amp; x);</code>
1855
1856 <blockquote>
1857 <b>Effects:</b> Constructs a <code>composite_key_hash</code> that stores
1858 copies of the hash functors supplied in <code>x</code>.
1859 </blockquote>
1860
1861 <code>const key_hasher_tuple&amp; key_hash_functions()const;</code>
1862
1863 <blockquote>
1864 <b>Returns:</b> a constant reference to a tuple holding the
1865 hash functors internally stored by the
1866 <code>composite_key_hash</code>.
1867 </blockquote>
1868
1869 <code>key_hasher_tuple&amp; key_hash_functions();</code>
1870
1871 <blockquote>
1872 <b>Returns:</b> a reference to a tuple holding the
1873 hash functors internally stored by the
1874 <code>composite_key_hash</code>.
1875 </blockquote>
1876
1877 <code>
1878 template&lt;typename CompositeKey><br>
1879 bool operator()(<br>
1880 &nbsp;&nbsp;const composite_key_result&lt;CompositeKey>&amp; x)const;<br>
1881 template&lt;typename... Values><br>
1882 bool operator()(<br>
1883 &nbsp;&nbsp;const std::tuple&lt;Values...>&amp; x)const;<br>
1884 template&lt;typename Value0,...,typename Valuen><br>
1885 bool operator()(<br>
1886 &nbsp;&nbsp;const boost::tuple&lt;Value0,...,Valuen>&amp; x)const;
1887 </code>
1888
1889 <blockquote>
1890 <b>Requires:</b> <code>length(x)==length(key_hash_functions())</code>.
1891 The expression
1892 <code>key_hash_functions().get&lt;i>()(x<sub>i</sub>)</code>
1893 is valid for all <code>i</code> in <code>[0,length(x))</code>.
1894 <br>
1895 <b>Returns:</b> A value in the range
1896 <code>[0, std::numeric_limits&lt;std::size_t&gt;::max())</code> that
1897 solely depends on the numerical tuple
1898 <blockquote>
1899 (<code>key_hash_functions().get&lt;0>()(x<sub>0</sub>)</code>, ... ,
1900 <code>key_hash_functions().get&lt;N>()(x<sub>N</sub>)</code>),
1901 with <code>N=length(x)-1</code>.
1902 </blockquote>
1903 </blockquote>
1904
1905 <h4><a name="composite_key_result_hash">Class template
1906 <code>composite_key_result_hash</code></a></h4>
1907
1908 <p>
1909 Deprecated. Use <code>boost::hash&lt;CompositeKeyResult&gt;</code> instead.
1910 </p>
1911
1912 <h4><a name="hash_composite_key_result">Specialization of
1913 <a href="../../../functional/hash/index.html"><code>boost::hash</code></a>
1914 for <code>composite_key</code> results</a></h4>
1915
1916 <p>
1917 <code>boost::hash&lt;CompositeKeyResult></code>, with <code>CompositeKeyResult</code>
1918 an instantiation of <code>composite_key_result</code>, behaves as a particularization of
1919 <code>composite_key_hash</code> where all the hash functors supplied
1920 are instantiations of
1921 <a href="../../../functional/hash/index.html"><code>boost::hash</code></a>.
1922 </p>
1923
1924 <blockquote><pre>
1925 <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
1926
1927 <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1928 <span class=keyword>struct</span> <span class=identifier>hash</span><span class=special>&lt;</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=special>&gt;</span>
1929 <span class=special>{</span>
1930   <span class=keyword>typedef</span> <span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;</span> <span class=identifier>argument_type</span><span class=special>;</span>
1931   <span class=keyword>typedef</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span>                                     <span class=identifier>result_type</span><span class=special>;</span>
1932
1933   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>&gt;</span>
1934   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1935     <span class=keyword>const</span> <span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special>&lt;</span><span class=identifier>CompositeKey</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1936
1937   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span><span class=special>...</span> <span class=identifier>Values</span><span class=special>&gt;</span>
1938   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1939     <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Values</span><span class=special>...&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1940
1941   <span class=keyword>template</span><span class=special>&lt;</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>&gt;</span>
1942   <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span>
1943     <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>&gt;&amp;</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
1944 <span class=special>};</span>
1945
1946 <span class=special>}</span> <span class=comment>// namespace boost</span>
1947 </pre></blockquote>
1948
1949 <p>
1950 <code>CompositeKeyResult</code> must be an instantiation of
1951 <code>composite_key_result</code> for some type
1952 <code>composite_key&lt;KeyFromValue0,...,KeyFromValuen></code>.
1953 <code>boost::hash&lt;CompositeKeyResult>::operator()</code> is
1954 then equivalent to
1955 <code>composite_key_hash&lt;Hash0,...,Hashn>::operator()</code>, taking
1956 <blockquote>
1957 <code>Hashi = boost::hash&lt;KeyFromValuei::result_type></code> for all
1958 <code>i = 0,...,n</code>.
1959 </blockquote>
1960 </p>
1961
1962 <p>
1963 In addition to the requirements on <code>Hashi</code> imposed by
1964 <code>composite_key_hash</code>, each of these types must be
1965 <code>DefaultConstructible</code>. <code>boost::hash&lt;CompositeKeyResult></code> is
1966 <code>DefaultConstructible</code>, <code>CopyConstructible</code>
1967 and <code>CopyAssignable</code>.
1968 </p>
1969
1970 <h3><a name="ckey_result_semantics">Semantics of
1971 <code>composite_key_result</code></a></h3>
1972
1973 <p>
1974 The design of equality, comparison and hash operations for
1975 <code>composite_key_result</code> objects is based on the following rationale:
1976 a <code>composite_key_result</code> is regarded as a "virtual" tuple, each
1977 of its elements being the result of the corresponding elementary
1978 key extractor. Accordingly, any given operation resolves to a
1979 combination of the corresponding elementwise operations.
1980 This mapping preserves the fundamental properties of the elementary operations
1981 involved; for instance, it defines a true equivalence relation if the
1982 basic predicates induce equivalence relations themselves.
1983 We can state these facts in a formal way as follows.
1984 </p>
1985
1986 <p>
1987 Consider an instantiation of <code>composite_key_equal_to</code>
1988 with types <code>Pred0</code>, ... , <code>Predn</code> such that each
1989 <code>Predi</code> induces an equivalence relation on a certain type <code>Ti</code>,
1990 and let <code>CompositeKey</code> be a type of the form
1991 <code>composite_key&lt;Value,KeyFromValue0,...,KeyFromValuej></code>,
1992 with <code>j &lt;= n</code>, such that
1993 <blockquote>
1994 <code>KeyFromValuei::result_type = Ti</code>, for all <code>i = 0,...,j</code>.
1995 </blockquote>
1996 Then, <code>composite_key_equal_to</code> induces an equivalence relation
1997 on elements of type <code>composite_key_result&lt;CompositeKey></code>;
1998 such two objects are equivalent if all its elementary key extractor values
1999 are also equivalent. Additionally, given an instantiation
2000 <code>composite_key_hash&lt;Hash0,...,Hashj></code>, the following types are
2001 <a href="hash_indices.html#lookup"><code>Compatible Keys</code></a> of
2002 (<code>composite_key_hash</code>, <code>composite_key_equal_to</code>)
2003 with respect to <code>composite_key_result&lt;CompositeKey></code>:
2004 <blockquote>
2005 <code>tuple&lt;Q0,...,Qj></code>,<br>
2006 <code>composite_key_result&lt;composite_key&lt;K0,...,Kj> ></code>, with
2007 <code>Ki::result_type = Qi</code> for all <code>i = 0,...,j</code>.
2008 </blockquote>
2009 provided that each <code>Qi</code> is either <code>Ti</code> or a
2010 <a href="hash_indices.html#lookup"><code>Compatible Key</code></a>
2011 of (<code>Hashi</code>, <code>Predi</code>).</p>
2012
2013 <p>
2014 As for comparison, consider an instantiation of <code>composite_key_compare</code>
2015 with types <code>Compare0</code>, ... , <code>Comparen</code> such that each
2016 <code>Comparei</code> induces a strict weak ordering
2017 on the type <code>Ti</code>. Then, for a
2018 <code>CompositeKey</code> type defined in the same manner as above,
2019 <code>composite_key_compare</code> induces a strict weak ordering on elements of type
2020 <code>composite_key_result&lt;CompositeKey></code>, and the order induced
2021 is lexicographical. Also, the following types are
2022 <a href="ord_indices.html#set_operations"><code>Compatible Keys</code></a> of
2023 <code>composite_key_compare</code> with respect to
2024 <code>composite_key_result&lt;CompositeKey></code>:
2025 <blockquote>
2026 <code>tuple&lt;Q0,...,Qk></code>, <code>k &lt;= n</code><br>
2027 <code>composite_key_result&lt;composite_key&lt;K0,...,Kk> ></code>, with
2028 <code>Ki::result_type = Qi</code> for all <code>i = 0,...,k</code>.
2029 </blockquote>
2030 provided that
2031 <ul>
2032   <li>for <code>i = 0,...,min(j,k)-1</code>, <code>Qi</code> is either <code>Ti</code>
2033     or <i>not coarser</i> than <code>Ti</code> (<code>Qi</code> is a
2034     <a href="ord_indices.html#set_operations"><code>Compatible Key</code></a>
2035     of <code>Comparei</code> and there are no two distinct elements of
2036     <code>Ti</code> equivalent to one single element of <code>Qi</code>);
2037   </li>
2038   <li>
2039     <code>Qm</code> (with <code>m = min(j,k)</code>) is either <code>Tm</code> or a
2040     <a href="ord_indices.html#set_operations"><code>Compatible Key</code></a>
2041     of <code>Comparem</code>.
2042   </li>
2043 </ul>
2044
2045 In this case, the comparison is done
2046 lexicographically only on the first <code>1+min(j,k)</code> elements.
2047 </p>
2048
2049 <p>
2050 Analogous properties hold for the equality and comparison operators
2051 of <code>composite_key_result</code>. Note, however,
2052 that equality is only defined for objects of the same length, whilst
2053 comparison takes the minimum length of the operands considered.
2054 Therefore, the equivalence classes induced by <code>x==y</code> are
2055 subsets of those associated to <code>!(x&lt;y)&amp;&amp;!(y&lt;x)</code>.
2056 </p>
2057
2058 <hr>
2059
2060 <div class="prev_link"><a href="rnd_indices.html"><img src="../prev.gif" alt="random access indices" border="0"><br>
2061 Random access indices
2062 </a></div>
2063 <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex reference" border="0"><br>
2064 Boost.MultiIndex reference
2065 </a></div>
2066 <div class="next_link"><a href="../compiler_specifics.html"><img src="../next.gif" alt="compiler specifics" border="0"><br>
2067 Compiler specifics
2068 </a></div><br clear="all" style="clear: all;">
2069
2070 <br>
2071
2072 <p>Revised August 20th 2014</p>
2073
2074 <p>&copy; Copyright 2003-2014 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
2075 Distributed under the Boost Software
2076 License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
2077 LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
2078 http://www.boost.org/LICENSE_1_0.txt</a>)
2079 </p>
2080
2081 </body>
2082 </html>