62 lines
6.5 KiB
HTML
62 lines
6.5 KiB
HTML
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_random_uniform_random_bit_generator skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>uniform_random_bit_generator</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-numeric.html">numeric</a>‎ | <a href="cpp-numeric-random.html">random</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-random.html"><random></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> G<span class="sy1">></span><br /></span>
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<p>concept uniform_random_bit_generator <span class="sy1">=</span><br />
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std<span class="sy4">::</span><span class="me2">invocable</span><span class="sy1"><</span>G<span class="sy3">&</span><span class="sy1">></span> <span class="sy3">&&</span> std<span class="sy4">::</span><span class="me2">unsigned_integral</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">invoke_result_t</span><span class="sy1"><</span>G<span class="sy3">&</span><span class="sy1">>></span> <span class="sy3">&&</span><br />
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requires <span class="br0">{</span><br />
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<span class="br0">{</span> G<span class="sy4">::</span><span class="me2">min</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> std<span class="sy4">::</span><span class="me2">same_as</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">invoke_result_t</span><span class="sy1"><</span>G<span class="sy3">&</span><span class="sy1">>></span><span class="sy4">;</span><br />
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<span class="br0">{</span> G<span class="sy4">::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> std<span class="sy4">::</span><span class="me2">same_as</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">invoke_result_t</span><span class="sy1"><</span>G<span class="sy3">&</span><span class="sy1">>></span><span class="sy4">;</span><br />
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requires <a href="cpp-types-integral_constant.html"><span class="kw648">std::<span class="me2">bool_constant</span></span></a><span class="sy1"><</span><span class="br0">(</span>G<span class="sy4">::</span><span class="me2">min</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><</span> G<span class="sy4">::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">value</span><span class="sy4">;</span><br /></p>
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<span class="br0">}</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p>概念 <code>uniform_random_bit_generator<G></code> 指定 <code>G</code> 为均匀随机位生成器的类型，即 <code>G</code> 类型对象是函数对象，返回无符号整数值，并使得可能结果范围中的每个值（理论上）拥有相等的被返回概率。</p>
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<h3><span class="mw-headline" id=".E8.AF.AD.E4.B9.89.E8.A6.81.E6.B1.82">语义要求</span></h3>
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<p><code>uniform_random_bit_generator<G></code> 仅若符合下列条件才得到实现。给定 <code>G</code> 类型对象 <code>g</code> ：</p>
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<ul>
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<li><code>g()</code> 在范围 <code>[G::min(), G::max()]</code> 中</li>
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<li><code>g()</code> 拥有均摊常数复杂度</li>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp">requires <a href="cpp-types-integral_constant.html"><span class="kw648">std::<span class="me2">bool_constant</span></span></a><span class="sy1"><</span><span class="br0">(</span>G<span class="sy4">::</span><span class="me2">min</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><</span> G<span class="sy4">::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">value</span><span class="sy4">;</span></span></span> 要求仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp">G<span class="sy4">::</span><span class="me2">min</span><span class="br0">(</span><span class="br0">)</span></span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">G<span class="sy4">::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span></span></span> 均为常量表达式，且比较结果为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 才得到满足。</p>
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