1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Advanced lookup and insertion functions for associative containers</title> 6<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../intrusive.html" title="Chapter 19. Boost.Intrusive"> 10<link rel="prev" href="bst_hooks.html" title="Binary search tree hooks: bs_set_base_hook and bs_set_member_hook"> 11<link rel="next" href="erasing_and_disposing.html" title="Erasing and disposing values from Boost.Intrusive containers"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> 16<td align="center"><a href="../../../index.html">Home</a></td> 17<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="bst_hooks.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="erasing_and_disposing.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="intrusive.advanced_lookups_insertions"></a><a class="link" href="advanced_lookups_insertions.html" title="Advanced lookup and insertion functions for associative containers">Advanced lookup 29 and insertion functions for associative containers</a> 30</h2></div></div></div> 31<div class="toc"><dl class="toc"> 32<dt><span class="section"><a href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_lookups">Advanced 33 lookups</a></span></dt> 34<dt><span class="section"><a href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_insertions">Advanced 35 insertions</a></span></dt> 36<dt><span class="section"><a href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.positional_insertions">Positional 37 insertions</a></span></dt> 38</dl></div> 39<div class="section"> 40<div class="titlepage"><div><div><h3 class="title"> 41<a name="intrusive.advanced_lookups_insertions.advanced_lookups"></a><a class="link" href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_lookups" title="Advanced lookups">Advanced 42 lookups</a> 43</h3></div></div></div> 44<div class="toc"><dl class="toc"><dt><span class="section"><a href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_lookups.advanced_lookups_example">Example</a></span></dt></dl></div> 45<p> 46 <span class="bold"><strong>Boost.Intrusive</strong></span> associative containers offer 47 an interface similar to STL associative containers. However, STL's ordered 48 and unordered simple associative containers (<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">set</span></code>, 49 <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">multiset</span></code>, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_set</span></code> 50 and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_multiset</span></code>) have some inefficiencies 51 caused by the interface in several search, insertion or erasure functions 52 (<code class="computeroutput"><span class="identifier">equal_range</span></code>, <code class="computeroutput"><span class="identifier">lower_bound</span></code>, <code class="computeroutput"><span class="identifier">upper_bound</span></code>, 53 <code class="computeroutput"><span class="identifier">find</span></code>, <code class="computeroutput"><span class="identifier">insert</span></code>, 54 <code class="computeroutput"><span class="identifier">erase</span></code>...): the user can only 55 operate with <code class="computeroutput"><span class="identifier">value_type</span></code> objects 56 or (starting from C++11), <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3657.htm" target="_top">heterogeneous 57 comparison lookups</a> which are not flexible enough as <code class="computeroutput"><span class="identifier">key_compare</span></code> shall support the comparison 58 between the provided key and <code class="computeroutput"><span class="identifier">value_type</span></code>, 59 which precludes the use of user-defined comparison objects that can partition 60 the search in a compatible but advanced way. 61 </p> 62<p> 63 To solve these problems, <span class="bold"><strong>Boost.Intrusive</strong></span> 64 containers offers functions where a key type different from <code class="computeroutput"><span class="identifier">key_type</span></code> and a comparison object are provided 65 by the user. This applies to: * equal_range * lower_bound * upper_bound * 66 count * find * erase 67 </p> 68<p> 69 Requirements for such functions are: 70 </p> 71<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 72<li class="listitem"> 73 For unordered container the provided comparison and hashing function 74 with the given key shall induce the same hash and equivalence as <code class="computeroutput"><span class="identifier">key_compare</span></code> and <code class="computeroutput"><span class="identifier">hasher</span></code>. 75 </li> 76<li class="listitem"> 77 For ordered associative containers, lookup and erasure functions, the 78 container to be searched shall be partitioned in regards to the supplied 79 comparison object and key. 80 </li> 81</ul></div> 82<p> 83 For more details, see <span class="bold"><strong>Requires</strong></span> clauses of 84 such functions in the reference. 85 </p> 86<div class="section"> 87<div class="titlepage"><div><div><h4 class="title"> 88<a name="intrusive.advanced_lookups_insertions.advanced_lookups.advanced_lookups_example"></a><a class="link" href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_lookups.advanced_lookups_example" title="Example">Example</a> 89</h4></div></div></div> 90<p> 91 Imagine that the object to be searched is quite expensive to construct 92 (called <code class="computeroutput"><span class="identifier">Expensive</span></code> in the 93 example): 94 </p> 95<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 96<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">unordered_set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 97<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cstring</span><span class="special">></span> 98 99<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive</span><span class="special">;</span> 100 101<span class="comment">// Hash function for strings</span> 102<span class="keyword">struct</span> <span class="identifier">StrHasher</span> 103<span class="special">{</span> 104 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">str</span><span class="special">)</span> <span class="keyword">const</span> 105 <span class="special">{</span> 106 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">seed</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 107 <span class="keyword">for</span><span class="special">(;</span> <span class="special">*</span><span class="identifier">str</span><span class="special">;</span> <span class="special">++</span><span class="identifier">str</span><span class="special">)</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">hash_combine</span><span class="special">(</span><span class="identifier">seed</span><span class="special">,</span> <span class="special">*</span><span class="identifier">str</span><span class="special">);</span> 108 <span class="keyword">return</span> <span class="identifier">seed</span><span class="special">;</span> 109 <span class="special">}</span> 110<span class="special">};</span> 111 112<span class="keyword">class</span> <span class="identifier">Expensive</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">set_base_hook</span><span class="special"><>,</span> <span class="keyword">public</span> <span class="identifier">unordered_set_base_hook</span><span class="special"><></span> 113<span class="special">{</span> 114 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">key_</span><span class="special">;</span> 115 <span class="comment">// Other members...</span> 116 117 <span class="keyword">public</span><span class="special">:</span> 118 <span class="identifier">Expensive</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">key</span><span class="special">)</span> 119 <span class="special">:</span> <span class="identifier">key_</span><span class="special">(</span><span class="identifier">key</span><span class="special">)</span> 120 <span class="special">{}</span> <span class="comment">//other expensive initializations...</span> 121 122 <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&</span> <span class="identifier">get_key</span><span class="special">()</span> <span class="keyword">const</span> 123 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">key_</span><span class="special">;</span> <span class="special">}</span> 124 125 <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special"><</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> 126 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">key_</span> <span class="special"><</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">key_</span><span class="special">;</span> <span class="special">}</span> 127 128 <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> 129 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">key_</span> <span class="special">==</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">key_</span><span class="special">;</span> <span class="special">}</span> 130 131 <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">hash_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">object</span><span class="special">)</span> 132 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">StrHasher</span><span class="special">()(</span><span class="identifier">object</span><span class="special">.</span><span class="identifier">get_key</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">());</span> <span class="special">}</span> 133<span class="special">};</span> 134 135<span class="comment">// A set and unordered_set that store Expensive objects</span> 136<span class="keyword">typedef</span> <span class="identifier">set</span><span class="special"><</span><span class="identifier">Expensive</span><span class="special">></span> <span class="identifier">Set</span><span class="special">;</span> 137<span class="keyword">typedef</span> <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">Expensive</span><span class="special">></span> <span class="identifier">UnorderedSet</span><span class="special">;</span> 138 139<span class="comment">// Search functions</span> 140<span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">get_from_set</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">Set</span> <span class="special">&</span><span class="identifier">set_object</span><span class="special">)</span> 141<span class="special">{</span> 142 <span class="identifier">Set</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">Expensive</span><span class="special">(</span><span class="identifier">key</span><span class="special">));</span> 143 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">it</span> <span class="special">==</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">)</span> <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 144 <span class="keyword">return</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">;</span> 145<span class="special">}</span> 146 147<span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">get_from_uset</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">UnorderedSet</span> <span class="special">&</span><span class="identifier">uset_object</span><span class="special">)</span> 148<span class="special">{</span> 149 <span class="identifier">UnorderedSet</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">Expensive</span> <span class="special">(</span><span class="identifier">key</span><span class="special">));</span> 150 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">it</span> <span class="special">==</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">)</span> <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 151 <span class="keyword">return</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">;</span> 152<span class="special">}</span> 153</pre> 154<p> 155 If "key" c-string is quite long <code class="computeroutput"><span class="identifier">Expensive</span></code> 156 has to construct a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code> 157 using heap memory. Like <code class="computeroutput"><span class="identifier">Expensive</span></code>, 158 many times the only member taking part in ordering issues is just a small 159 part of the class. E.g.: with <code class="computeroutput"><span class="identifier">Expensive</span></code>, 160 only the internal <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code> is needed to compare the object. 161 </p> 162<p> 163 In both containers, if we call <code class="computeroutput"><span class="identifier">get_from_set</span><span class="special">/</span><span class="identifier">get_from_unordered_set</span></code> 164 in a loop, we might get a performance penalty, because we are forced to 165 create a whole <code class="computeroutput"><span class="identifier">Expensive</span></code> 166 object to be able to find an equivalent one. 167 </p> 168<p> 169 Sometimes the problem is not only performance-related, as we <span class="bold"><strong>might not have enough information to construct the object</strong></span> 170 but we might <span class="bold"><strong>have enough information to find the 171 object</strong></span>. In this case, a name is enough to search <code class="computeroutput"><span class="identifier">Expensive</span></code> objects in the container but 172 constructing an <code class="computeroutput"><span class="identifier">Expensive</span></code> 173 object might require more information that the searcher might not have. 174 </p> 175<p> 176 To solve this, we can use the functions that take any type comparable with 177 the value and a the 'compatible' comparison object (and hash, when the 178 associative container is unordered) Let's see optimized search function: 179 </p> 180<pre class="programlisting"><span class="comment">// These compare Expensive and a c-string</span> 181<span class="keyword">struct</span> <span class="identifier">StrExpComp</span> 182<span class="special">{</span> 183 <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">str</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> 184 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">strcmp</span><span class="special">(</span><span class="identifier">str</span><span class="special">,</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">get_key</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">())</span> <span class="special"><</span> <span class="number">0</span><span class="special">;</span> <span class="special">}</span> 185 186 <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">c</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">str</span><span class="special">)</span> <span class="keyword">const</span> 187 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">strcmp</span><span class="special">(</span><span class="identifier">c</span><span class="special">.</span><span class="identifier">get_key</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">(),</span> <span class="identifier">str</span><span class="special">)</span> <span class="special"><</span> <span class="number">0</span><span class="special">;</span> <span class="special">}</span> 188<span class="special">};</span> 189 190<span class="keyword">struct</span> <span class="identifier">StrExpEqual</span> 191<span class="special">{</span> 192 <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">str</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> 193 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">strcmp</span><span class="special">(</span><span class="identifier">str</span><span class="special">,</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">get_key</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">())</span> <span class="special">==</span> <span class="number">0</span><span class="special">;</span> <span class="special">}</span> 194 195 <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="identifier">Expensive</span> <span class="special">&</span><span class="identifier">c</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">str</span><span class="special">)</span> <span class="keyword">const</span> 196 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">strcmp</span><span class="special">(</span><span class="identifier">c</span><span class="special">.</span><span class="identifier">get_key</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">(),</span> <span class="identifier">str</span><span class="special">)</span> <span class="special">==</span> <span class="number">0</span><span class="special">;</span> <span class="special">}</span> 197<span class="special">};</span> 198 199<span class="comment">// Optimized search functions</span> 200<span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">get_from_set_optimized</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">Set</span> <span class="special">&</span><span class="identifier">set_object</span><span class="special">)</span> 201<span class="special">{</span> 202 <span class="identifier">Set</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">key</span><span class="special">,</span> <span class="identifier">StrExpComp</span><span class="special">());</span> 203 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">it</span> <span class="special">==</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">)</span> <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 204 <span class="keyword">return</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">;</span> 205<span class="special">}</span> 206 207<span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">get_from_uset_optimized</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">UnorderedSet</span> <span class="special">&</span><span class="identifier">uset_object</span><span class="special">)</span> 208<span class="special">{</span> 209 <span class="identifier">UnorderedSet</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">key</span><span class="special">,</span> <span class="identifier">StrHasher</span><span class="special">(),</span> <span class="identifier">StrExpEqual</span><span class="special">());</span> 210 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">it</span> <span class="special">==</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">)</span> <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 211 <span class="keyword">return</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">;</span> 212<span class="special">}</span> 213</pre> 214</div> 215</div> 216<div class="section"> 217<div class="titlepage"><div><div><h3 class="title"> 218<a name="intrusive.advanced_lookups_insertions.advanced_insertions"></a><a class="link" href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_insertions" title="Advanced insertions">Advanced 219 insertions</a> 220</h3></div></div></div> 221<div class="toc"><dl class="toc"><dt><span class="section"><a href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_insertions.advanced_insertions_example">Example</a></span></dt></dl></div> 222<p> 223 A similar issue happens with insertions in simple ordered and unordered associative 224 containers with unique keys (<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">set</span></code> and 225 <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_set</span></code>). In these containers, if 226 a value is already present, the value to be inserted is discarded. With expensive 227 values, if the value is already present, we can suffer efficiency problems. 228 </p> 229<p> 230 <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code> and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code>-like 231 containers have insertion functions (<code class="computeroutput"><span class="identifier">insert_check</span></code>, 232 <code class="computeroutput"><span class="identifier">insert_unique_check</span></code>,...) 233 to check efficiently, without constructing the value, if a value is present 234 or not and if it's not present, a function to insert it immediately (<code class="computeroutput"><span class="identifier">insert_commit</span></code>) without any further lookup. 235 Requirements for functions that check the existence of such value are: 236 </p> 237<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 238<li class="listitem"> 239 For unordered container the provided comparison and hashing function 240 with the given key shall induce the same hash and equivalence as <code class="computeroutput"><span class="identifier">key_compare</span></code> and <code class="computeroutput"><span class="identifier">hasher</span></code>. 241 </li> 242<li class="listitem"> 243 For ordered associative containers, the provided comparison function 244 with the given key, shall induce the same strict weak order as <code class="computeroutput"><span class="identifier">key_compare</span></code>. 245 </li> 246</ul></div> 247<p> 248 To sum up, <code class="computeroutput"><span class="identifier">insert_check</span></code> is 249 similar to a normal <code class="computeroutput"><span class="identifier">insert</span></code> 250 but: 251 </p> 252<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 253<li class="listitem"> 254 <code class="computeroutput"><span class="identifier">insert_check</span></code> can be used 255 with arbitrary keys 256 </li> 257<li class="listitem"> 258 if the insertion is possible (there is no equivalent value) <code class="computeroutput"><span class="identifier">insert_check</span></code> collects all the needed 259 information in an <code class="computeroutput"><span class="identifier">insert_commit_data</span></code> 260 structure, so that <code class="computeroutput"><span class="identifier">insert_commit</span></code>: 261 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> 262<li class="listitem"> 263 <span class="bold"><strong>does not execute</strong></span> further comparisons 264 </li> 265<li class="listitem"> 266 can be executed with <span class="bold"><strong>constant-time complexity</strong></span> 267 </li> 268<li class="listitem"> 269 has <span class="bold"><strong>no-throw guarantee</strong></span>. 270 </li> 271</ul></div> 272 </li> 273</ul></div> 274<p> 275 These functions must be used with care, no other insertion or erasure must 276 be executed between an <code class="computeroutput"><span class="identifier">insert_check</span></code> 277 and an <code class="computeroutput"><span class="identifier">insert_commit</span></code> pair. 278 Otherwise, the behaviour is undefined. 279 </p> 280<p> 281 See <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code> and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code>-like containers' 282 reference for more information about <code class="computeroutput"><span class="identifier">insert_check</span></code> 283 and <code class="computeroutput"><span class="identifier">insert_commit</span></code>. 284 </p> 285<p> 286 With multiple ordered and unordered associative containers (<code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code> 287 and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code>) 288 there is no need for these advanced insertion functions, since insertions 289 are always successful. 290 </p> 291<div class="section"> 292<div class="titlepage"><div><div><h4 class="title"> 293<a name="intrusive.advanced_lookups_insertions.advanced_insertions.advanced_insertions_example"></a><a class="link" href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.advanced_insertions.advanced_insertions_example" title="Example">Example</a> 294</h4></div></div></div> 295<p> 296 For example, using the same <code class="computeroutput"><span class="identifier">Expensive</span></code> 297 class, this function can be inefficient: 298 </p> 299<pre class="programlisting"><span class="comment">// Insertion functions</span> 300<span class="keyword">bool</span> <span class="identifier">insert_to_set</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">Set</span> <span class="special">&</span><span class="identifier">set_object</span><span class="special">)</span> 301<span class="special">{</span> 302 <span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">pobject</span> <span class="special">=</span> <span class="keyword">new</span> <span class="identifier">Expensive</span><span class="special">(</span><span class="identifier">key</span><span class="special">);</span> 303 <span class="keyword">bool</span> <span class="identifier">success</span> <span class="special">=</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">pobject</span><span class="special">).</span><span class="identifier">second</span><span class="special">;</span> 304 <span class="keyword">if</span><span class="special">(!</span><span class="identifier">success</span><span class="special">)</span> <span class="keyword">delete</span> <span class="identifier">pobject</span><span class="special">;</span> 305 <span class="keyword">return</span> <span class="identifier">success</span><span class="special">;</span> 306<span class="special">}</span> 307 308<span class="keyword">bool</span> <span class="identifier">insert_to_uset</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">UnorderedSet</span> <span class="special">&</span><span class="identifier">uset_object</span><span class="special">)</span> 309<span class="special">{</span> 310 <span class="identifier">Expensive</span> <span class="special">*</span><span class="identifier">pobject</span> <span class="special">=</span> <span class="keyword">new</span> <span class="identifier">Expensive</span><span class="special">(</span><span class="identifier">key</span><span class="special">);</span> 311 <span class="keyword">bool</span> <span class="identifier">success</span> <span class="special">=</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">pobject</span><span class="special">).</span><span class="identifier">second</span><span class="special">;</span> 312 <span class="keyword">if</span><span class="special">(!</span><span class="identifier">success</span><span class="special">)</span> <span class="keyword">delete</span> <span class="identifier">pobject</span><span class="special">;</span> 313 <span class="keyword">return</span> <span class="identifier">success</span><span class="special">;</span> 314<span class="special">}</span> 315</pre> 316<p> 317 If the object is already present, we are constructing an <code class="computeroutput"><span class="identifier">Expensive</span></code> that will be discarded, and 318 this is a waste of resources. Instead of that, let's use <code class="computeroutput"><span class="identifier">insert_check</span></code> and <code class="computeroutput"><span class="identifier">insert_commit</span></code> 319 functions: 320 </p> 321<pre class="programlisting"><span class="comment">// Optimized insertion functions</span> 322<span class="keyword">bool</span> <span class="identifier">insert_to_set_optimized</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">Set</span> <span class="special">&</span><span class="identifier">set_object</span><span class="special">)</span> 323<span class="special">{</span> 324 <span class="identifier">Set</span><span class="special">::</span><span class="identifier">insert_commit_data</span> <span class="identifier">insert_data</span><span class="special">;</span> 325 <span class="keyword">bool</span> <span class="identifier">success</span> <span class="special">=</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">insert_check</span><span class="special">(</span><span class="identifier">key</span><span class="special">,</span> <span class="identifier">StrExpComp</span><span class="special">(),</span> <span class="identifier">insert_data</span><span class="special">).</span><span class="identifier">second</span><span class="special">;</span> 326 <span class="keyword">if</span><span class="special">(</span><span class="identifier">success</span><span class="special">)</span> <span class="identifier">set_object</span><span class="special">.</span><span class="identifier">insert_commit</span><span class="special">(*</span><span class="keyword">new</span> <span class="identifier">Expensive</span><span class="special">(</span><span class="identifier">key</span><span class="special">),</span> <span class="identifier">insert_data</span><span class="special">);</span> 327 <span class="keyword">return</span> <span class="identifier">success</span><span class="special">;</span> 328<span class="special">}</span> 329 330<span class="keyword">bool</span> <span class="identifier">insert_to_uset_optimized</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">key</span><span class="special">,</span> <span class="identifier">UnorderedSet</span> <span class="special">&</span><span class="identifier">uset_object</span><span class="special">)</span> 331<span class="special">{</span> 332 <span class="identifier">UnorderedSet</span><span class="special">::</span><span class="identifier">insert_commit_data</span> <span class="identifier">insert_data</span><span class="special">;</span> 333 <span class="keyword">bool</span> <span class="identifier">success</span> <span class="special">=</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">insert_check</span> 334 <span class="special">(</span><span class="identifier">key</span><span class="special">,</span> <span class="identifier">StrHasher</span><span class="special">(),</span> <span class="identifier">StrExpEqual</span><span class="special">(),</span> <span class="identifier">insert_data</span><span class="special">).</span><span class="identifier">second</span><span class="special">;</span> 335 <span class="keyword">if</span><span class="special">(</span><span class="identifier">success</span><span class="special">)</span> <span class="identifier">uset_object</span><span class="special">.</span><span class="identifier">insert_commit</span><span class="special">(*</span><span class="keyword">new</span> <span class="identifier">Expensive</span><span class="special">(</span><span class="identifier">key</span><span class="special">),</span> <span class="identifier">insert_data</span><span class="special">);</span> 336 <span class="keyword">return</span> <span class="identifier">success</span><span class="special">;</span> 337<span class="special">}</span> 338</pre> 339</div> 340</div> 341<div class="section"> 342<div class="titlepage"><div><div><h3 class="title"> 343<a name="intrusive.advanced_lookups_insertions.positional_insertions"></a><a class="link" href="advanced_lookups_insertions.html#intrusive.advanced_lookups_insertions.positional_insertions" title="Positional insertions">Positional 344 insertions</a> 345</h3></div></div></div> 346<p> 347 Some ordered associative containers offer low-level functions to bypass ordering 348 checks and insert nodes directly in desired tree positions. These functions 349 are provided for performance reasons when values to be inserted in the container 350 are known to fulfill order (sets and multisets) and uniqueness (sets) invariants. 351 A typical usage of these functions is when intrusive associative containers 352 are used to build non-intrusive containers and the programmer wants to speed 353 up assignments from other associative containers: if the ordering and uniqueness 354 properties are the same, there is no need to waste time checking the position 355 of each source value, because values are already ordered: back insertions 356 will be much more efficient. 357 </p> 358<p> 359 <span class="bold"><strong>Note:</strong></span> These functions <span class="bold"><strong>don't 360 check preconditions</strong></span> so they must used with care. They are low-level 361 operations that <span class="bold"><strong>will break container invariants if 362 ordering and uniqueness preconditions are not assured by the caller.</strong></span> 363 </p> 364<p> 365 Let's see an example: 366 </p> 367<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 368<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span> 369<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">functional</span><span class="special">></span> 370<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> 371 372<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive</span><span class="special">;</span> 373 374<span class="comment">//A simple class with a set hook</span> 375<span class="keyword">class</span> <span class="identifier">MyClass</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">set_base_hook</span><span class="special"><></span> 376<span class="special">{</span> 377 <span class="keyword">public</span><span class="special">:</span> 378 <span class="keyword">int</span> <span class="identifier">int_</span><span class="special">;</span> 379 380 <span class="identifier">MyClass</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">int_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{}</span> 381 <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> 382 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special"><</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> 383 <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> 384 <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special">></span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> 385<span class="special">};</span> 386 387<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 388<span class="special">{</span> 389 <span class="comment">//Create some ORDERED elements</span> 390 <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">values</span><span class="special">;</span> 391 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyClass</span><span class="special">(</span><span class="identifier">i</span><span class="special">));</span> 392 393 <span class="special">{</span> <span class="comment">//Data is naturally ordered in the vector with the same criteria</span> 394 <span class="comment">//as multiset's comparison predicate, so we can just push back</span> 395 <span class="comment">//all elements, which is more efficient than normal insertion</span> 396 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">mset</span><span class="special">;</span> 397 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">mset</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">values</span><span class="special">[</span><span class="identifier">i</span><span class="special">]);</span> 398 399 <span class="comment">//Now check orderd invariant</span> 400 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">const_iterator</span> <span class="identifier">next</span><span class="special">(</span><span class="identifier">mset</span><span class="special">.</span><span class="identifier">cbegin</span><span class="special">()),</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">next</span><span class="special">++);</span> 401 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">99</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">,</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">next</span><span class="special">)</span> <span class="identifier">assert</span><span class="special">(*</span><span class="identifier">it</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">next</span><span class="special">);</span> 402 <span class="special">}</span> 403 <span class="special">{</span> <span class="comment">//Now the correct order for the set is the reverse order</span> 404 <span class="comment">//so let's push front all elements</span> 405 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">compare</span><span class="special"><</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">greater</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">mset</span><span class="special">;</span> 406 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">mset</span><span class="special">.</span><span class="identifier">push_front</span><span class="special">(</span><span class="identifier">values</span><span class="special">[</span><span class="identifier">i</span><span class="special">]);</span> 407 408 <span class="comment">//Now check orderd invariant</span> 409 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">compare</span><span class="special"><</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">greater</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="special">></span> <span class="special">>::</span> 410 <span class="identifier">const_iterator</span> <span class="identifier">next</span><span class="special">(</span><span class="identifier">mset</span><span class="special">.</span><span class="identifier">cbegin</span><span class="special">()),</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">next</span><span class="special">++);</span> 411 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">99</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">,</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">next</span><span class="special">)</span> <span class="identifier">assert</span><span class="special">(*</span><span class="identifier">it</span> <span class="special">></span> <span class="special">*</span><span class="identifier">next</span><span class="special">);</span> 412 <span class="special">}</span> 413 <span class="special">{</span> <span class="comment">//Now push the first and the last and insert the rest</span> 414 <span class="comment">//before the last position using "insert_before"</span> 415 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">mset</span><span class="special">;</span> 416 <span class="identifier">mset</span><span class="special">.</span><span class="identifier">insert_before</span><span class="special">(</span><span class="identifier">mset</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">values</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span> 417 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">const_iterator</span> <span class="identifier">pos</span> <span class="special">=</span> 418 <span class="identifier">mset</span><span class="special">.</span><span class="identifier">insert_before</span><span class="special">(</span><span class="identifier">mset</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">values</span><span class="special">[</span><span class="number">99</span><span class="special">]);</span> 419 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">99</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">mset</span><span class="special">.</span><span class="identifier">insert_before</span><span class="special">(</span><span class="identifier">pos</span><span class="special">,</span> <span class="identifier">values</span><span class="special">[</span><span class="identifier">i</span><span class="special">]);</span> 420 421 <span class="comment">//Now check orderd invariant</span> 422 <span class="identifier">multiset</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">const_iterator</span> <span class="identifier">next</span><span class="special">(</span><span class="identifier">mset</span><span class="special">.</span><span class="identifier">cbegin</span><span class="special">()),</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">next</span><span class="special">++);</span> 423 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">99</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">,</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">next</span><span class="special">)</span> <span class="identifier">assert</span><span class="special">(*</span><span class="identifier">it</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">next</span><span class="special">);</span> 424 <span class="special">}</span> 425 426 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 427<span class="special">}</span> 428</pre> 429</div> 430<p> 431 For more information about advanced lookup and insertion functions see associative 432 containers' documentation (e.g. <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code>, 433 <code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code>, <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> references). 434 </p> 435</div> 436<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 437<td align="left"></td> 438<td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2015 Ion Gaztanaga<p> 439 Distributed under the Boost Software License, Version 1.0. (See accompanying 440 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 441 </p> 442</div></td> 443</tr></table> 444<hr> 445<div class="spirit-nav"> 446<a accesskey="p" href="bst_hooks.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../intrusive.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="erasing_and_disposing.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 447</div> 448</body> 449</html> 450
