58 lines
4.8 KiB
HTML
58 lines
4.8 KiB
HTML
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::experimental::ranges::</span>Predicate</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-experimental.html">experimental</a>‎ | <a href="cpp-experimental-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-experimental-ranges-concepts.html"><experimental/ranges/concepts></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> F, <span class="kw1">class</span>... <span class="me1">Args</span> <span class="sy1">></span><br /></span>
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<p>concept <span class="kw4">bool</span> Predicate <span class="sy1">=</span><br />
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<a href="cpp-experimental-ranges-concepts-Invocable.html"><span class="kw2557">ranges::<span class="me2">RegularInvocable</span></span></a><span class="sy1"><</span>F, Args...<span class="sy1">></span> <span class="sy3">&&</span><br /></p>
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<a href="cpp-experimental-ranges-concepts-Boolean.html"><span class="kw2541">ranges::<span class="me2">Boolean</span></span></a><span class="sy1"><</span><a href="cpp-types-result_of.html"><span class="kw640">std::<span class="me2">result_of_t</span></span></a><span class="sy1"><</span>F<span class="sy3">&&</span><span class="br0">(</span>Args<span class="sy3">&&</span>...<span class="br0">)</span><span class="sy1">>></span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-ranges-ts t-mark-ts">(范围 TS)</span></td>
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<p>概念 <code>Predicate<F, Args...></code> 指定 <code>F</code> 是谓词并接受类型和值类别由 <code>Args...</code> 编码的参数，即能以这些参数调用它以产生 <a href="cpp-experimental-ranges-concepts-Boolean.html"><code>Boolean</code></a> 结果。</p>
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<p>注意 <a href="cpp-experimental-ranges-concepts-Invocable.html"><code>RegularInvocable</code></a> 要求调用既不修改可调用对象亦不修改参数，且保持相等性。</p>
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<h3><span class="mw-headline" id=".E7.9B.B8.E7.AD.89.E6.80.A7.E4.BF.9D.E6.8C.81">相等性保持</span></h3>
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<p>若表达式对给定的相等输入产生相等输出，则它<i>保持相等性</i>。</p>
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<li>表达式的输入由其运算数组成。</li>
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<li>表达式的输出由其结果和表达式所修改的所有运算数（若存在）组成。</li>
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<p>进一步要求每个要求保持相等性的表达式都<i>稳定</i>：这种表达式带相同输入对象的二次求值必须拥有相等的输出，而无任何对这些输入对象的显式中间修改。</p>
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