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<strong class="selflink"><tt>std::random_device</tt></strong><div class="t-navbar-menu"><div><div>
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</tr>
<tr><td colspan="3" class="t-ddcl-list-sep"></td></tr>
<tr class="t-ddcl-list-item">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> random_device<span class="sy4">;</span></span></div>
</td>
<td class="t-ddcl-list-item-nopad">  </td>
<td> <span class="t-mark">(since C++11)</span> </td>
</tr>
<tr><td colspan="3" class="t-ddcl-list-sep"></td></tr>
</table>
<p><tt>std::random_device</tt> is a uniformly-distributed integer random number generator, which produces non-deterministic random numbers, if a non-deterministic source (e.g. a hardware device) is available to the implementation.
</p>
<table id="toc" class="toc"><tr><td>
<div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="#Member_types"><span class="tocnumber">1</span> <span class="toctext">Member types</span></a></li>
<li class="toclevel-1 tocsection-2">
<a href="#Member_functions"><span class="tocnumber">2</span> <span class="toctext">Member functions</span></a>
<ul>
<li class="toclevel-2"><a href="#Construction"><span class="tocnumber">2.1</span> <span class="toctext">Construction</span></a></li>
<li class="toclevel-2"><a href="#Generation"><span class="tocnumber">2.2</span> <span class="toctext">Generation</span></a></li>
<li class="toclevel-2"><a href="#Characteristics"><span class="tocnumber">2.3</span> <span class="toctext">Characteristics</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-3"><a href="#Example"><span class="tocnumber">3</span> <span class="toctext">Example</span></a></li>
</ul>
</td></tr></table>
<h3>
<span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/random_device&amp;action=edit&amp;section=1" title="Edit section: Member types">edit</a>]</span> <span class="mw-headline" id="Member_types">Member types</span>
</h3>
<table class="t-dcl-list-begin">
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-hitem">
<td>  Member type
</td>
<td>  Definition
</td>
</tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <tt>result_type</tt>
</td>
<td>  <span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">int</span></span>
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/random_device&amp;action=edit&amp;section=2" title="Edit section: Member functions">edit</a>]</span> <span class="mw-headline" id="Member_functions">Member functions</span>
</h3>
<table class="t-dcl-list-begin">
<tr><td colspan="2"> <h5> <span class="mw-headline" id="Construction">  Construction </span>
</h5>
</td></tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div t-dcl-member-nobold-div"><div><a href="random_device/random_device.html" title="cpp/numeric/random/random device/random device"> (constructor)</a></div></div>
</td>
<td>  constructs the engine <br><span class="t-mark">(public member function)</span> 
</td>
</tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div">
<div>operator=</div>
<div><span class="t-mark">(deleted)</span></div>
</div>
</td>
<td>   the assignment operator is deleted <br><span class="t-mark">(public member function)</span>
</td>
</tr>
<tr><td colspan="2"> <h5> <span class="mw-headline" id="Generation">  Generation </span>
</h5>
</td></tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div"><div><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/random_device/operator()&amp;action=edit&amp;redlink=1" class="new" title="cpp/numeric/random/random device/operator() (page does not exist)"> operator()</a></div></div>
</td>
<td>   advances the engine's state and returns the generated value <br><span class="t-mark">(public member function)</span> 
</td>
</tr>
<tr><td colspan="2"> <h5> <span class="mw-headline" id="Characteristics">  Characteristics </span>
</h5>
</td></tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div"><div><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/random_device/entropy&amp;action=edit&amp;redlink=1" class="new" title="cpp/numeric/random/random device/entropy (page does not exist)"> entropy</a></div></div>
</td>
<td>   obtains the entropy estimate for the non-deterministic random number generator  <br><span class="t-mark">(public member function)</span> 
</td>
</tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div">
<div><a href="random_device/min.html" title="cpp/numeric/random/random device/min"> min</a></div>
<div><span class="t-cmark">[static]</span></div>
</div>
</td>
<td>   gets the smallest possible value in the output range <br><span class="t-mark">(public static member function)</span> 
</td>
</tr>
<tr><td colspan="2" class="t-dcl-list-sep">
</td></tr>
<tr class="t-dcl-list-item">
<td>  <div class="t-dcl-member-div">
<div><a href="random_device/max.html" title="cpp/numeric/random/random device/max"> max</a></div>
<div><span class="t-cmark">[static]</span></div>
</div>
</td>
<td>   gets the largest possible value in the output range <br><span class="t-mark">(public static member function)</span> 
</td>
</tr>
</table>
<h3>
<span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/random_device&amp;action=edit&amp;section=3" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span>
</h3>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="co2">#include &lt;map&gt;</span>
<span class="co2">#include &lt;random&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    std<span class="sy4">::</span><span class="me2">random_device</span> rd<span class="sy4">;</span>
    <a href="../../container/map.html"><span class="kw1061">std::<span class="me2">map</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="kw4">int</span><span class="sy1">&gt;</span> hist<span class="sy4">;</span>
    <span class="kw1">for</span><span class="br0">(</span><span class="kw4">int</span> n<span class="sy1">=</span><span class="nu0">0</span><span class="sy4">;</span> n<span class="sy1">&lt;</span><span class="nu0">20000</span><span class="sy4">;</span> <span class="sy2">++</span>n<span class="br0">)</span>
        <span class="sy2">++</span>hist<span class="br0">[</span>rd<span class="br0">(</span><span class="br0">)</span><span class="sy2">%</span><span class="nu19">10</span><span class="br0">]</span><span class="sy4">;</span>
    <span class="kw1">for</span><span class="br0">(</span><span class="kw4">auto</span> p <span class="sy4">:</span> hist<span class="br0">)</span>
        <a href="../../io/basic_ostream.html"><span class="kw1418">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> p.<span class="me1">first</span> <span class="sy1">&lt;&lt;</span> <span class="st0">" : "</span> <span class="sy1">&lt;&lt;</span> <a href="../../string/basic_string.html"><span class="kw1034">std::<span class="me2">string</span></span></a><span class="br0">(</span>p.<span class="me1">second</span><span class="sy2">/</span><span class="nu0">100</span>, <span class="st0">'*'</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">0 : ********************
1 : *******************
2 : ********************
3 : ********************
4 : ********************
5 : *******************
6 : ********************
7 : ********************
8 : *******************
9 : ********************</pre></div></div>

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