131 lines
9.8 KiB
HTML
131 lines
9.8 KiB
HTML
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<title>std::boolalpha, std::noboolalpha</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_manip_boolalpha 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>boolalpha, <span style="font-size:0.7em; line-height:130%">std::</span>noboolalpha</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-manip.html">manip</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-ios.html"><ios></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> boolalpha<span class="br0">(</span> <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> noboolalpha<span class="br0">(</span> <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<div class="t-li1"><span class="t-li">1)</span> 启用流 <code>str</code> 中的 <code>boolalpha</code> 标志,如同通过调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">setf</span><span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1690">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">boolalpha</span></span></a><span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 禁用流 <code>str</code> 中的 <code>boolalpha</code> 标志,如同通过调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">unsetf</span><span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1690">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">boolalpha</span></span></a><span class="br0">)</span></span></span> 。</div>
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<p><code>std::boolalpha</code> 是 I/O 操纵符,故可用如 <span class="t-c"><span class="mw-geshi cpp source-cpp">out <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">boolalpha</span></span></span> 的表达式对任何 <span class="t-lc"><a href="cpp-io-basic_ostream.html">std::basic_ostream</a></span> 类型的 <code>out</code> ,或用如 <span class="t-c"><span class="mw-geshi cpp source-cpp">in <span class="sy1">>></span> std<span class="sy4">::</span><span class="me2">boolalpha</span></span></span> 的表达式对任何 <span class="t-lc"><a href="cpp-io-basic_istream.html">std::basic_istream</a></span> 类型的 <code>in</code> 调用。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>str</td>
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<td>-</td>
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<td>到 I/O 流的引用</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p><code>str</code> (到操纵后的流的引用)</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <sstream></span>
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<span class="co2">#include <locale></span>
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<span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="co1">// boolalpha 输出</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">boolalpha</span>
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<span class="sy1"><<</span> <span class="st0">"boolalpha true: "</span> <span class="sy1"><<</span> <span class="kw2">true</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"boolalpha false: "</span> <span class="sy1"><<</span> <span class="kw2">false</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">noboolalpha</span>
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<span class="sy1"><<</span> <span class="st0">"noboolalpha true: "</span> <span class="sy1"><<</span> <span class="kw2">true</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"noboolalpha false: "</span> <span class="sy1"><<</span> <span class="kw2">false</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="co1">// boolalpha 分析</span>
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<span class="kw4">bool</span> b1, b2<span class="sy4">;</span>
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<a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a> is<span class="br0">(</span><span class="st0">"true false"</span><span class="br0">)</span><span class="sy4">;</span>
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is <span class="sy1">>></span> std<span class="sy4">::</span><span class="me2">boolalpha</span> <span class="sy1">>></span> b1 <span class="sy1">>></span> b2<span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\"</span>'</span> <span class="sy1"><<</span> is.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span> parsed as "</span> <span class="sy1"><<</span> b1 <span class="sy1"><<</span> <span class="st0">' '</span> <span class="sy1"><<</span> b2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出:</p>
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<div class="text source-text">
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<pre class="de1">boolalpha true: true
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boolalpha false: false
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noboolalpha true: 1
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noboolalpha false: 0
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"true false" parsed as 1 0</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-manip-resetiosflags.html"><span class="t-lines"><span>resetiosflags</span></span></a></div>
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<td>清除指定的 ios_base 标志<br />
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<span class="t-mark">(函数)</span></td>
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<div><a href="cpp-io-manip-setiosflags.html"><span class="t-lines"><span>setiosflags</span></span></a></div>
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<td>设置指定的 ios_base 标志<br />
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<span class="t-mark">(函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-locale-numpunct-truefalsename.html"><span class="t-lines"><span>do_truename</span><span>do_falsename</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div>
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<td>提供用作布尔 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 名称的字符串<br />
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<span class="t-mark">(<code>std::numpunct<CharT></code> 的虚受保护成员函数)</span></td>
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<div class="visualClear"></div>
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