390 lines
47 KiB
HTML
390 lines
47 KiB
HTML
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<title>std::num_put<CharT,OutputIt>::put, std::num_put<CharT,OutputIt>::do_put</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::num_put<CharT,OutputIt>::</span>put, <span style="font-size:0.7em; line-height:130%">std::num_put<CharT,OutputIt>::</span>do_put</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-locale.html">locale</a>‎ | <a href="cpp-locale-num_put.html">num put</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-locale.html"><locale></a></code></div>
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<td rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">public</span><span class="sy4">:</span><br />
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iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">bool</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">unsigned</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">double</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> <span class="kw4">double</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">iter_type put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">const</span> <span class="kw4">void</span><span class="sy2">*</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td rowspan="142">(2)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br />
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<span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">bool</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">unsigned</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">double</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">long</span> <span class="kw4">double</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> iter_type do_put<span class="br0">(</span> iter_type out, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> str, char_type fill, <span class="kw4">const</span> <span class="kw4">void</span><span class="sy2">*</span> v <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div class="t-li1"><span class="t-li">1)</span> 公开成员函数，调用最终导出类的受保护虚成员函数 <code>do_put</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 写字符到输出序列 <code>out</code> ，这些字符表示 <code>v</code> 的值，按格式化标志 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span></span></span> 和流 <code>str</code> 中感染的 locale 的 <span class="t-lc"><a href="cpp-locale-numpunct.html">std::numpunct</a></span> 和 <span class="t-lc"><a href="cpp-locale-ctype.html">std::ctype</a></span> 平面所要求者格式化。此函数为所有有格式输出流运算符，如 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> n<span class="sy4">;</span></span></span> 所调用。</div>
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<p>转换以四个阶段出现</p>
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<h4><span class="mw-headline" id=".E9.98.B6.E6.AE.B5_1_.EF.BC.9A.E8.BD.AC.E6.8D.A2.E8.AF.B4.E6.98.8E.E7.AC.A6.E9.80.89.E6.8B.A9">阶段 1 ：转换说明符选择</span></h4>
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<li>获得 I/O 格式标志，如同以</li>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags basefield <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1682">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">basefield</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags uppercase <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1696">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">uppercase</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags floatfield <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1689">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">floatfield</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags showpos <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1693">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">showpos</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags showbase <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1691">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">showbase</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<dd><span class="t-c"><span class="mw-geshi cpp source-cpp">fmtflags showpoint <span class="sy1">=</span> <span class="br0">(</span>str.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1692">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">showpoint</span></span></a><span class="br0">)</span><span class="sy4">;</span></span></span></dd>
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<li>若 <code>v</code> 的类型为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span></span></span>
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<ul>
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<li>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">boolalpha <span class="sy1">==</span> <span class="nu0">0</span></span></span> ，则转换 <code>v</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span> 类型并进行整数输出。</li>
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<li>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">boolalpha <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">0</span></span></span> ，则若 <span class="t-c"><span class="mw-geshi cpp source-cpp">v <span class="sy1">==</span> <span class="kw2">true</span></span></span> 则获得<span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-numpunct.html"><span class="kw1961">std::<span class="me2">numpunct</span></span></a><span class="sy1"><</span>charT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">truename</span><span class="br0">(</span><span class="br0">)</span></span></span> ，或若 <span class="t-c"><span class="mw-geshi cpp source-cpp">v <span class="sy1">==</span> <span class="kw2">false</span></span></span> 则获得 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-numpunct.html"><span class="kw1961">std::<span class="me2">numpunct</span></span></a><span class="sy1"><</span>charT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">falsename</span><span class="br0">(</span><span class="br0">)</span></span></span> ，并以 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>out<span class="sy2">++</span> <span class="sy1">=</span> c</span></span> 输出该字符串的每个相继字符 <code>c</code> 到 <code>out</code> 。此情况下不进行进一步的操作，函数返回 <code>out</code> 。</li>
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<li>若 <code>v</code> 的类型为整数类型，则选择下列首个可应用选项：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">basefield <span class="sy1">==</span> oct</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>o</span></span></dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">basefield <span class="sy1">==</span> hex <span class="sy3">&&</span> <span class="sy3">!</span>uppercase</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>x</span></span></dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">basefield <span class="sy1">==</span> hex</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>X</span></span></dd>
|
|
<dd>若 <code>v</code> 的类型有符号，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>d</span></span></dd>
|
|
<dd>若 <code>v</code> 的类型无符号，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>u</span></span></dd>
|
|
</dl>
|
|
<ul>
|
|
<li>对于整数类型，若需要则添加长度修饰符到转换说明：对于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">l</span></span> ，对于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">ll</span></span> 。</li>
|
|
<li>若 <code>v</code> 为浮点类型，则选择首个可应用选项：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1688">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">fixed</span></span></a></span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>f</span></span></dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1687">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">scientific</span></span></a> <span class="sy3">&&</span> <span class="sy3">!</span>uppercase</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>e</span></span></dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1687">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">scientific</span></span></a></span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>E</span></span></dd>
|
|
</dl>
|
|
<table class="t-rev-begin">
|
|
<tr class="t-rev t-since-cxx11">
|
|
<td>
|
|
<dl>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1688">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">fixed</span></span></a> <span class="sy3">|</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1687">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">scientific</span></span></a><span class="br0">)</span> <span class="sy3">&&</span> <span class="sy3">!</span>uppercase</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>a</span></span></dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1688">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">fixed</span></span></a> <span class="sy3">|</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1687">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">scientific</span></span></a><span class="br0">)</span></span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>A</span></span></dd>
|
|
</dl>
|
|
</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
</table>
|
|
<dl>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>uppercase</span></span> ，则将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>g</span></span></dd>
|
|
<dd>否则，将使用转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>G</span></span>
|
|
<ul>
|
|
<li>若 <code>v</code> 的类型为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span></span></span> ，则添加长度修饰符 <span class="t-c"><span class="mw-geshi cpp source-cpp">L</span></span> 到转换说明符。</li>
|
|
<li>另外<span class="t-rev-inl t-since-cxx11"><span>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy3">!</span><span class="sy1">=</span> <span class="br0">(</span>ios_base<span class="sy4">::</span><span class="me2">fixed</span> <span class="sy3">|</span> ios_base<span class="sy4">::</span><span class="me2">scientific</span><span class="br0">)</span></span></span> 则</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span>添加设为 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">precision</span><span class="br0">(</span><span class="br0">)</span></span></span> 的精度说明符</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
<ul>
|
|
<li>对于整数和浮点类型，若设置了 <span class="t-c"><span class="mw-geshi cpp source-cpp">showpos</span></span> ，则前附修饰符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">+</span></span></span> 。</li>
|
|
<li>对于整数类型，若设置了 <span class="t-c"><span class="mw-geshi cpp source-cpp">showbase</span></span> ，则前附修饰符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="co2">#</span></span></span> 。</li>
|
|
<li>对于浮点类型，若设置了 <span class="t-c"><span class="mw-geshi cpp source-cpp">showpoint</span></span> ，则前附修饰符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="co2">#</span></span></span> 。</li>
|
|
<li>若 <code>v</code> 的类型为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><span class="sy2">*</span></span></span> ，则将使用格式说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>p</span></span> 。</li>
|
|
<li>如同以在 "C" 本地环境中调用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-io-c-fprintf.html"><span class="kw1845">std::<span class="me2">printf</span></span></a><span class="br0">(</span>spec, v<span class="br0">)</span></span></span> 创建窄字符串，其中 <code>spec</code> 是所选的格式说明符。</li>
|
|
</ul>
|
|
<h4><span class="mw-headline" id=".E9.98.B6.E6.AE.B5_2_.EF.BC.9A.E6.9C.AC.E5.9C.B0.E7.8E.AF.E5.A2.83.E9.99.90.E5.AE.9A.E8.BD.AC.E6.8D.A2">阶段 2 ：本地环境限定转换</span></h4>
|
|
<ul>
|
|
<li>调用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-ctype.html"><span class="kw1938">std::<span class="me2">ctype</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">widen</span><span class="br0">(</span>c<span class="br0">)</span></span></span> ，将阶段 1 中获得的每个异于小数点 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'.'</span></span></span> 的字符 <code>c</code> 转换为 <code>CharT</code> 。</li>
|
|
<li>对于算术类型，按照 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-numpunct.html"><span class="kw1961">std::<span class="me2">numpunct</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">grouping</span><span class="br0">(</span><span class="br0">)</span></span></span> 所提供的分组规则，插入从 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-numpunct.html"><span class="kw1961">std::<span class="me2">numpunct</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">thousands_sep</span><span class="br0">(</span><span class="br0">)</span></span></span> 获得的千分隔字符到序列中。</li>
|
|
<li>以 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-numpunct.html"><span class="kw1961">std::<span class="me2">numpunct</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>str.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">decimal_point</span><span class="br0">(</span><span class="br0">)</span></span></span> 替换小数点字符（ <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'.'</span></span></span> ）。</li>
|
|
</ul>
|
|
<h4><span class="mw-headline" id=".E9.98.B6.E6.AE.B5_3_.EF.BC.9A.E5.A1.AB.E5.85.85">阶段 3 ：填充</span></h4>
|
|
<ul>
|
|
<li>如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">fmtflags</span> adjustfield <span class="sy1">=</span> <span class="br0">(</span>flags <span class="sy3">&</span> <span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1686">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">adjustfield</span></span></a><span class="br0">)</span><span class="br0">)</span></span></span> 获得调整标志，并以如下方式检验它以鉴别填充位置</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">adjustfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1683">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">left</span></span></a></span></span> ，则将在后方填充</dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">adjustfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1684">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">right</span></span></a></span></span> ，则将在前方填充</dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">adjustfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1685">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">internal</span></span></a></span></span> 且表示中出现符号字符，则将在符号后填充</dd>
|
|
<dd>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">adjustfield <span class="sy1">==</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1685">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">internal</span></span></a></span></span> 而阶段 1 表示以 0x 或 0X 开始，则将在 x 或 X 后填充</dd>
|
|
<dd>否则，将在前方填充</dd>
|
|
</dl>
|
|
<ul>
|
|
<li>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">width</span><span class="br0">(</span><span class="br0">)</span></span></span> 非零（例如刚使用了 <span class="t-lc"><a href="cpp-io-manip-setw.html">std::setw</a></span> ）且阶段 2 后的 CharT 数小于 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">width</span><span class="br0">(</span><span class="br0">)</span></span></span> ，则插入 <span class="t-c"><span class="mw-geshi cpp source-cpp">fill</span></span> 字符的副本于填充所指示的位置，令序列长度达到 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">width</span><span class="br0">(</span><span class="br0">)</span></span></span> 。</li>
|
|
</ul>
|
|
<p>任何情况下，都调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">str.<span class="me1">width</span><span class="br0">(</span><span class="nu0">0</span><span class="br0">)</span></span></span> 以取消 <span class="t-lc"><a href="cpp-io-manip-setw.html">std::setw</a></span> 的效果。</p>
|
|
<h4><span class="mw-headline" id=".E9.98.B6.E6.AE.B5_4_.EF.BC.9A.E8.BE.93.E5.87.BA">阶段 4 ：输出</span></h4>
|
|
<p>如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>out<span class="sy2">++</span> <span class="sy1">=</span> c</span></span> 输出来自阶段 3 的 CharT 序列的每个相继字符 <code>c</code> 。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>out</td>
|
|
<td>-</td>
|
|
<td>指向首个要写入字符的迭代器</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>str</td>
|
|
<td>-</td>
|
|
<td>取得格式化信息来源的流</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>fill</td>
|
|
<td>-</td>
|
|
<td>需要填充结果到域宽时使用的填充字符</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>v</td>
|
|
<td>-</td>
|
|
<td>转换为字符串并输出的值</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p><code>out</code></p>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>转换说明 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="co2">#o</span></span></span> （例如产生自 <span class="t-lc"><a href="cpp-io-manip-showbase.html">std::showbase</a></span> 和 <span class="t-lc"><a href="cpp-io-manip-hex.html">std::oct</a></span> 的组合）不计为填充字符。</p>
|
|
<table class="t-rev-begin">
|
|
<tr class="t-rev t-since-cxx11">
|
|
<td>
|
|
<p>格式化浮点值为 hexfloat 时（即 <span class="t-c"><span class="mw-geshi cpp source-cpp">floatfield <span class="sy1">==</span> <span class="br0">(</span><a href="cpp-io-ios_base-fmtflags.html"><span class="kw1688">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">fixed</span></span></a> <span class="sy3">|</span> <a href="cpp-io-ios_base-fmtflags.html"><span class="kw1687">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">scientific</span></span></a><span class="br0">)</span></span></span> 时），不使用流的精度；而是始终以足以准确表示值的精度打印该数。</p>
|
|
</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<p>用平面直接输出数，并演示用户定义的平面</p>
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <locale></span>
|
|
|
|
<span class="co1">// 此定制 num_put 平面输出所有整数类型的平方（除了 long long ）</span>
|
|
<span class="kw1">struct</span> squaring_num_put <span class="sy4">:</span> <a href="cpp-locale-num_put.html"><span class="kw1958">std::<span class="me2">num_put</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span> <span class="br0">{</span>
|
|
iter_type do_put<span class="br0">(</span>iter_type s, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> f,
|
|
char_type fill, <span class="kw4">long</span> v<span class="br0">)</span> <span class="kw4">const</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">return</span> <a href="cpp-locale-num_put.html"><span class="kw1958">std::<span class="me2">num_put</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">do_put</span><span class="br0">(</span>s, f, fill, v<span class="sy2">*</span>v <span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
iter_type do_put<span class="br0">(</span>iter_type s, <a href="cpp-io-ios_base.html"><span class="kw1669">std::<span class="me2">ios_base</span></span></a><span class="sy3">&</span> f,
|
|
char_type fill, <span class="kw4">unsigned</span> <span class="kw4">long</span> v<span class="br0">)</span> <span class="kw4">const</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-locale-num_put.html"><span class="kw1958">std::<span class="me2">num_put</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">do_put</span><span class="br0">(</span>s, f, fill, v<span class="sy2">*</span>v<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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|
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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="kw4">auto</span><span class="sy3">&</span> facet <span class="sy1">=</span> <a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-num_put.html"><span class="kw1958">std::<span class="me2">num_put</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">>></span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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facet.<span class="me1">put</span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>, <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>, <span class="st0">'0'</span>, <span class="nu16">2.71</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<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">\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="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span>, new squaring_num_put<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="nu0">6</span> <span class="sy1"><<</span> <span class="st0">' '</span> <span class="sy1"><<</span> <span class="sy2">-</span><span class="nu0">12</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
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</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">2.71
|
|
36 144</pre></div>
|
|
</div>
|
|
</div>
|
|
<div class="t-example">
|
|
<p>用户定义类型的 <span class="t-lc">operator<<</span> 的实现。</p>
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <iterator></span>
|
|
<span class="co2">#include <locale></span>
|
|
|
|
<span class="kw1">struct</span> base <span class="br0">{</span> <span class="kw4">long</span> x <span class="sy1">=</span> <span class="nu0">10</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> CharT, <span class="kw1">class</span> Traits<span class="sy1">></span>
|
|
<a href="cpp-io-basic_ostream.html"><span class="kw1715">std::<span class="me2">basic_ostream</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="sy3">&</span>
|
|
operator<span class="sy1"><<</span> <span class="br0">(</span><a href="cpp-io-basic_ostream.html"><span class="kw1715">std::<span class="me2">basic_ostream</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="sy3">&</span> os, base <span class="kw4">const</span><span class="sy3">&</span> b<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">try</span> <span class="br0">{</span>
|
|
<span class="kw1">typename</span> <a href="cpp-io-basic_ostream.html"><span class="kw1715">std::<span class="me2">basic_ostream</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="sy4">::</span><span class="me2">sentry</span> s<span class="br0">(</span>os<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span>s<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-iterator-ostreambuf_iterator.html"><span class="kw671">std::<span class="me2">ostreambuf_iterator</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> it<span class="br0">(</span>os<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-num_put.html"><span class="kw1958">std::<span class="me2">num_put</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>os.<span class="me1">getloc</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
|
|
.<span class="me1">put</span><span class="br0">(</span>it, os, os.<span class="me1">fill</span><span class="br0">(</span><span class="br0">)</span>, b.<span class="me1">x</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span> <span class="kw1">catch</span> <span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="co1">// 设置 os 上的 badbit ，而且若要求则重抛出</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw1">return</span> os<span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
base b<span class="sy4">;</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> b<span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">10</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-io-basic_ostream-operator_ltlt.html"><span class="t-lines"><span>operator<<</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>插入带格式数据<br />
|
|
<span class="t-mark">(<code>std::basic_ostream<CharT,Traits></code> 的公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
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</div>
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|
</div>
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</body>
|
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</html>
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