90 lines
19 KiB
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90 lines
19 KiB
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<title>std::experimental::ranges::Boolean</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::experimental::ranges::</span>Boolean</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> B<span class="sy1">></span><br /></span>
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<p>concept <span class="kw4">bool</span> Boolean <span class="sy1">=</span><br />
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<a href="cpp-experimental-ranges-concepts-Movable.html"><span class="kw2551">ranges::<span class="me2">Movable</span></span></a><span class="sy1"><</span><a href="cpp-types-decay.html"><span class="kw629">std::<span class="me2">decay_t</span></span></a><span class="sy1"><</span>B<span class="sy1">>></span> <span class="sy3">&&</span><br />
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requires<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>B<span class="sy1">></span><span class="sy3">&</span> b1,<br />
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<span class="kw4">const</span> <a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>B<span class="sy1">></span><span class="sy3">&</span> b2, <span class="kw4">const</span> <span class="kw4">bool</span> a<span class="br0">)</span> <span class="br0">{</span><br />
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<span class="br0">{</span> b1 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> <span class="sy3">!</span>b1 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">&&</span> a <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">||</span> a <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">&&</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> a <span class="sy3">&&</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">||</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> a <span class="sy3">||</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-Same.html"><span class="kw2530">ranges::<span class="me2">Same</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy1">==</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy1">==</span> a <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> a <span class="sy1">==</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">!</span><span class="sy1">=</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> b1 <span class="sy3">!</span><span class="sy1">=</span> a <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</span><span class="sy4">;</span><br />
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<span class="br0">{</span> a <span class="sy3">!</span><span class="sy1">=</span> b2 <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <a href="cpp-experimental-ranges-concepts-ConvertibleTo.html"><span class="kw2532">ranges::<span class="me2">ConvertibleTo</span></span></a><span class="sy1"><</span><span class="kw4">bool</span><span class="sy1">></span><span class="sy3">&&</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-ranges-ts t-mark-ts">(范围 TS)</span></td>
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<p>概念 <code>Boolean<B></code> 指定可用于布尔语境的类型的要求。对于要满足 <code>Boolean</code> 的类型，逻辑运算符必须拥有通常行为（包括短路求值）。更精确地说，给定</p>
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<li><code>b1</code> 、 <code>b2</code> ，二个 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>B<span class="sy1">></span></span></span> 类型左值，</li>
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<p><code>Boolean<B></code> 仅若满足下列条件才得到满足：</p>
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<ul>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy1">==</span> <span class="sy3">!</span><span class="kw4">bool</span><span class="br0">(</span><span class="sy3">!</span>b1<span class="br0">)</span></span></span></li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp">b1 <span class="sy3">&&</span> b2</span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp">b1 <span class="sy3">&&</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">&&</span> b2</span></span> 全部等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">&&</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span></span></span> 并拥有相同的短路求值；</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp">b1 <span class="sy3">||</span> b2</span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp">b1 <span class="sy3">||</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">||</span> b2</span></span> 全部等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">||</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span></span></span> ，并拥有相同的短路求值；</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1 <span class="sy1">==</span> b2<span class="br0">)</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1 <span class="sy1">==</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span><span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy1">==</span> b2<span class="br0">)</span></span></span> 全部等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy1">==</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span><span class="br0">)</span></span></span> ；</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1 <span class="sy3">!</span><span class="sy1">=</span> b2<span class="br0">)</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span>b1 <span class="sy3">!</span><span class="sy1">=</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span><span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span><span class="br0">(</span><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> b2<span class="br0">)</span></span></span> 全部等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="kw4">bool</span><span class="br0">(</span>b1<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> <span class="kw4">bool</span><span class="br0">(</span>b2<span class="br0">)</span><span class="br0">)</span></span></span> 。</li>
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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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<ul>
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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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</ul>
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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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<p>除非另外提醒，每个用于 <i>requires 表达式</i>中的表达式都要求保持相等性且稳定，而表达式的求值必须只修改其非常运算数。必须不修改常运算数。</p>
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<h3><span class="mw-headline" id=".E9.9A.90.E5.BC.8F.E8.A1.A8.E8.BE.BE.E5.BC.8F.E5.8F.98.E7.A7.8D">隐式表达式变种</span></h3>
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<p>使用不修改某 const 左值运算数的表达式的 <i>requires 表达式</i>亦隐式要求该表达式的额外变种对给定运算数接受非 const 左值或（可为 const 的）右值，除非以有区别的语义显式要求这种表达式变种。这些<i>隐式表达式变种</i>必须符合与声明的表达式的相同的语义。不指定实现以何种程度校验变种的语法。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p><code>Boolean</code> 的例子包含 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-integral_constant.html"><span class="kw649">std::<span class="me2">true_type</span></span></a></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span>N<span class="sy1">></span><span class="sy4">::</span><span class="me2">reference</span></span></span> 。指针不是 <code>Boolean</code> 类型。</p>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">{</span> expression <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> Same<span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&&</span></span></span> 形式的推导制约等效地要求 <span class="t-c"><span class="mw-geshi cpp source-cpp">decltype<span class="br0">(</span><span class="br0">(</span>expression<span class="br0">)</span><span class="br0">)</span><span class="sy3">&&</span></span></span> 为与 <code>T&&</code> 准确相同的类型。这会制约表达式的类型与其值类别。</p>
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