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>Intrusive splay tree based associative containers: splay_set, splay_multiset and , splay_tree</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="avl_set_multiset.html" title="Intrusive avl tree based associative containers: avl_set, avl_multiset and avltree"> 11<link rel="next" href="sg_set_multiset.html" title="Intrusive scapegoat tree based associative containers: sg_set, sg_multiset and sgtree"> 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="avl_set_multiset.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="sg_set_multiset.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.splay_set_multiset"></a><a class="link" href="splay_set_multiset.html" title="Intrusive splay tree based associative containers: splay_set, splay_multiset and , splay_tree">Intrusive splay tree based 29 associative containers: splay_set, splay_multiset and , splay_tree</a> 30</h2></div></div></div> 31<div class="toc"><dl class="toc"> 32<dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_disadvantages">Advantages 33 and disadvantages of splay tree based containers</a></span></dt> 34<dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.set_multiset_containers">splay_set, 35 splay_multiset and splaytree containers</a></span></dt> 36<dt><span class="section"><a href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_example">Example</a></span></dt> 37</dl></div> 38<p> 39 C++ associative containers are usually based on red-black tree implementations 40 (e.g.: STL, Boost.Intrusive associative containers). However, there are other 41 interesting data structures that offer some advantages (and also disadvantages). 42 </p> 43<p> 44 Splay trees are self-adjusting binary search trees used typically in caches, 45 memory allocators and other applications, because splay trees have a "caching 46 effect": recently accessed elements have better access times than elements 47 accessed less frequently. For more information on splay trees see <a href="http://en.wikipedia.org/wiki/Splay_tree" target="_top">the 48 corresponding Wikipedia entry</a>. 49 </p> 50<p> 51 <span class="bold"><strong>Boost.Intrusive</strong></span> offers 3 containers based 52 on splay trees: <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_set.html" title="Class template splay_set">splay_set</a></code>, 53 <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_multiset.html" title="Class template splay_multiset">splay_multiset</a></code> 54 and <code class="computeroutput"><a class="link" href="../boost/intrusive/splaytree.html" title="Class template splaytree">splaytree</a></code>. The 55 first two are similar to <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code> 56 or <code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code> and the 57 latter is a generalization that offers functions both to insert unique and 58 multiple keys. 59 </p> 60<p> 61 The memory overhead of these containers with Boost.Intrusive hooks is usually 62 3 pointers. An empty, non constant-time size splay container has also a size 63 of 3 pointers. 64 </p> 65<div class="section"> 66<div class="titlepage"><div><div><h3 class="title"> 67<a name="intrusive.splay_set_multiset.splay_set_multiset_disadvantages"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_disadvantages" title="Advantages and disadvantages of splay tree based containers">Advantages 68 and disadvantages of splay tree based containers</a> 69</h3></div></div></div> 70<p> 71 Splay tree based intrusive containers have logarithmic complexity in many 72 operations like searches, insertions, erasures, etc., but if some elements 73 are more frequently accessed than others, splay trees perform faster searches 74 than equivalent balanced binary trees (such as red-black trees). 75 </p> 76<p> 77 The caching effect offered by splay trees comes with a cost: the tree must 78 be rebalanced when an element is searched. To maintain const-correctness 79 and thread-safety guarantees, this caching effect is not updated when const 80 versions of search functions like <code class="computeroutput"><span class="identifier">find</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">lower_bound</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">upper_bound</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">equal_range</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">count</span><span class="special">()</span></code>... are called. This means that using splay-tree 81 based associative containers as drop-in replacements of <code class="computeroutput"><a class="link" href="../boost/intrusive/set.html" title="Class template set">set</a></code>/ 82 <code class="computeroutput"><a class="link" href="../boost/intrusive/multiset.html" title="Class template multiset">multiset</a></code>, specially 83 for const search functions, might not result in desired performance improvements. 84 </p> 85<p> 86 If element searches are randomized, the tree will be continuously srebalanced 87 without taking advantage of the cache effect, so splay trees can offer worse 88 performance than other balanced trees for several search patterns. 89 </p> 90<p> 91 <span class="bold"><strong>Boost.Intrusive</strong></span> splay associative containers 92 don't use their own hook types but plain Binary search tree hooks. See <a class="link" href="bst_hooks.html" title="Binary search tree hooks: bs_set_base_hook and bs_set_member_hook">Binary search tree hooks: bs_set_base_hook 93 and bs_set_member_hook</a> section for more information about these hooks. 94 </p> 95</div> 96<div class="section"> 97<div class="titlepage"><div><div><h3 class="title"> 98<a name="intrusive.splay_set_multiset.set_multiset_containers"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.set_multiset_containers" title="splay_set, splay_multiset and splaytree containers">splay_set, 99 splay_multiset and splaytree containers</a> 100</h3></div></div></div> 101<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> 102<span class="keyword">class</span> <span class="identifier">splay_set</span><span class="special">;</span> 103 104<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> 105<span class="keyword">class</span> <span class="identifier">splay_multiset</span><span class="special">;</span> 106 107<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> 108<span class="keyword">class</span> <span class="identifier">splaytree</span><span class="special">;</span> 109</pre> 110<p> 111 These containers receive the same options explained in the section <a class="link" href="usage.html" title="How to use Boost.Intrusive">How to use Boost.Intrusive</a>: 112 </p> 113<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 114<li class="listitem"> 115 <span class="bold"><strong><code class="computeroutput"><span class="identifier">base_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">></span></code></strong></span> 116 / <span class="bold"><strong><code class="computeroutput"><span class="identifier">member_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">,</span> <span class="identifier">Hook</span> <span class="identifier">T</span><span class="special">::*</span> <span class="identifier">PtrToMember</span><span class="special">></span></code></strong></span> 117 / <span class="bold"><strong><code class="computeroutput"><span class="identifier">value_traits</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">ValueTraits</span><span class="special">></span></code></strong></span>: 118 To specify the hook type or value traits used to configure the container. 119 (To learn about value traits go to the section <a class="link" href="value_traits.html" title="Containers with custom ValueTraits">Containers 120 with custom ValueTraits</a>.) 121 </li> 122<li class="listitem"> 123 <span class="bold"><strong><code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: 124 To activate the constant-time <code class="computeroutput"><span class="identifier">size</span><span class="special">()</span></code> operation. Default: <code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">true</span><span class="special">></span></code> 125 </li> 126<li class="listitem"> 127 <span class="bold"><strong><code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="keyword">typename</span> 128 <span class="identifier">SizeType</span><span class="special">></span></code></strong></span>: 129 To specify the type that will be used to store the size of the container. 130 Default: <code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">></span></code> 131 </li> 132</ul></div> 133<p> 134 And they also can receive an additional option: 135 </p> 136<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 137<li class="listitem"> 138 <span class="bold"><strong><code class="computeroutput"><span class="identifier">compare</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Compare</span><span class="special">></span></code></strong></span>: 139 Comparison function for the objects to be inserted in containers. The 140 comparison functor must induce a strict weak ordering. Default: <code class="computeroutput"><span class="identifier">compare</span><span class="special"><</span> 141 <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special"><</span><span class="identifier">key_type</span><span class="special">></span> 142 <span class="special">></span></code> 143 </li> 144<li class="listitem"> 145 <span class="bold"><strong><code class="computeroutput"><span class="identifier">key_of_value</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">KeyOfValueFunctionObject</span><span class="special">></span></code></strong></span>: 146 A function object that will define the <code class="computeroutput"><span class="identifier">key_type</span></code> 147 of the value type to be stored. This type will allow a map-like interface. 148 See <a class="link" href="map_multimap.html" title="Map and multimap-like interface for associative containers">Map and multimap-like interface 149 with set and multiset</a> for details. Default: <code class="computeroutput"><span class="identifier">key_type</span></code> 150 is equal to <code class="computeroutput"><span class="identifier">value_type</span></code> 151 (set-like interface). 152 </li> 153</ul></div> 154</div> 155<div class="section"> 156<div class="titlepage"><div><div><h3 class="title"> 157<a name="intrusive.splay_set_multiset.splay_set_multiset_example"></a><a class="link" href="splay_set_multiset.html#intrusive.splay_set_multiset.splay_set_multiset_example" title="Example">Example</a> 158</h3></div></div></div> 159<p> 160 Now let's see a small example using <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_set.html" title="Class template splay_set">splay_set</a></code>/ 161 <code class="computeroutput"><a class="link" href="../boost/intrusive/splay_multiset.html" title="Class template splay_multiset">splay_multiset</a></code> 162 containers: 163 </p> 164<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">splay_set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 165<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span> 166<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">functional</span><span class="special">></span> 167 168<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> 169 170<span class="keyword">class</span> <span class="identifier">mytag</span><span class="special">;</span> 171 172<span class="keyword">class</span> <span class="identifier">MyClass</span> 173 <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bs_set_base_hook</span><span class="special"><></span> 174<span class="special">{</span> 175 <span class="keyword">int</span> <span class="identifier">int_</span><span class="special">;</span> 176 177 <span class="keyword">public</span><span class="special">:</span> 178 <span class="comment">//This is a member hook</span> 179 <span class="identifier">bs_set_member_hook</span><span class="special"><></span> <span class="identifier">member_hook_</span><span class="special">;</span> 180 181 <span class="identifier">MyClass</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> 182 <span class="special">:</span> <span class="identifier">int_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> 183 <span class="special">{}</span> 184 <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> 185 <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> 186 <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> 187 <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> 188 <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> 189 <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> 190<span class="special">};</span> 191 192<span class="comment">//Define a set using the base hook that will store values in reverse order</span> 193<span class="keyword">typedef</span> <span class="identifier">splay_set</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">BaseSplaySet</span><span class="special">;</span> 194 195<span class="comment">//Define an multiset using the member hook</span> 196<span class="keyword">typedef</span> <span class="identifier">member_hook</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">bs_set_member_hook</span><span class="special"><>,</span> <span class="special">&</span><span class="identifier">MyClass</span><span class="special">::</span><span class="identifier">member_hook_</span><span class="special">></span> <span class="identifier">MemberOption</span><span class="special">;</span> 197<span class="keyword">typedef</span> <span class="identifier">splay_multiset</span><span class="special"><</span> <span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">MemberOption</span><span class="special">></span> <span class="identifier">MemberSplayMultiset</span><span class="special">;</span> 198 199<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 200<span class="special">{</span> 201 <span class="keyword">typedef</span> <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">iterator</span> <span class="identifier">VectIt</span><span class="special">;</span> 202 203 <span class="comment">//Create several MyClass objects, each one with a different value</span> 204 <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> 205 <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> 206 207 <span class="identifier">BaseSplaySet</span> <span class="identifier">baseset</span><span class="special">;</span> 208 <span class="identifier">MemberSplayMultiset</span> <span class="identifier">membermultiset</span><span class="special">;</span> 209 210 211 <span class="comment">//Insert values in the container</span> 212 <span class="keyword">for</span><span class="special">(</span><span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">){</span> 213 <span class="identifier">baseset</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> 214 <span class="identifier">membermultiset</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> 215 <span class="special">}</span> 216 217 <span class="comment">//Now test sets</span> 218 <span class="special">{</span> 219 <span class="identifier">BaseSplaySet</span><span class="special">::</span><span class="identifier">reverse_iterator</span> <span class="identifier">rbit</span><span class="special">(</span><span class="identifier">baseset</span><span class="special">.</span><span class="identifier">rbegin</span><span class="special">());</span> 220 <span class="identifier">MemberSplayMultiset</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">mit</span><span class="special">(</span><span class="identifier">membermultiset</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> 221 <span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> 222 223 <span class="comment">//Test the objects inserted in the base hook set</span> 224 <span class="keyword">for</span><span class="special">(;</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</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">rbit</span><span class="special">){</span> 225 <span class="keyword">if</span><span class="special">(&*</span><span class="identifier">rbit</span> <span class="special">!=</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> 226 <span class="special">}</span> 227 228 <span class="comment">//Test the objects inserted in member and binary search hook sets</span> 229 <span class="keyword">for</span><span class="special">(</span><span class="identifier">it</span> <span class="special">=</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</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">mit</span><span class="special">){</span> 230 <span class="keyword">if</span><span class="special">(&*</span><span class="identifier">mit</span> <span class="special">!=</span> <span class="special">&*</span><span class="identifier">it</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> 231 <span class="special">}</span> 232 <span class="special">}</span> 233 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 234<span class="special">}</span> 235</pre> 236</div> 237</div> 238<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 239<td align="left"></td> 240<td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2015 Ion Gaztanaga<p> 241 Distributed under the Boost Software License, Version 1.0. (See accompanying 242 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>) 243 </p> 244</div></td> 245</tr></table> 246<hr> 247<div class="spirit-nav"> 248<a accesskey="p" href="avl_set_multiset.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="sg_set_multiset.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 249</div> 250</body> 251</html> 252
