211 lines
12 KiB
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211 lines
12 KiB
HTML
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<title>std::chrono::operator<< (std::chrono::duration)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>operator<< <span style="font-size:0.7em; line-height:130%">(std::chrono::duration)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a>‎ | <a href="cpp-chrono-duration.html">duration</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-chrono.html"><chrono></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> CharT, <span class="kw1">class</span> Traits, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period<span class="sy1">></span><br /></span>
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<p><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><br />
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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,<br /></p>
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<span class="kw4">const</span> <a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>Rep, Period<span class="sy1">></span><span class="sy3">&</span> d<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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<td></td>
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<p>插入 <code>d</code> 的文本表示到 <code>os</code> 中，若 <code>CharT</code> 既非 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 亦非 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> ，或若 <code>Rep</code> 既非浮点类型亦非转换等级大于或等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">short</span></span></span> 的类型，则行为未定义。</p>
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<p>表现如同它实现为</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><a href="cpp-io-basic_ostringstream.html"><span class="kw1722">std::<span class="me2">basic_ostringstream</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> s<span class="sy4">;</span>
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s.<span class="me1">flags</span><span class="br0">(</span>os.<span class="me1">flags</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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s.<span class="me1">imbue</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="sy4">;</span>
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s.<span class="me1">precision</span><span class="br0">(</span>os.<span class="me1">precision</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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s <span class="sy1"><<</span> d.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> units_suffix<span class="sy4">;</span> <span class="co1">// 见后述</span>
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<span class="kw1">return</span> os <span class="sy1"><<</span> s.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></pre></div>
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<p>换言之，流标志、本地环境和精度由流确定，但用整个输出字符串确定任何填充。</p>
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<p><code>units_suffix</code> 基于按照下表的 <code>Period::type</code> 确定。</p>
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<table class="t-dsc-begin">
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<tr class="t-dsc-hitem">
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<td><code>Period::type</code></td>
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<td>后缀</td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc">std::atto</span></td>
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<td><code>as</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::femto</a></span></td>
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<td><code>fs</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::pico</a></span></td>
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<td><code>ps</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::nano</a></span></td>
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<td><code>ns</code></td>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::micro</a></span></td>
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<td><code>µs</code> <span class="t-mark">(U+00B5)</span> 或 <code>us</code> ，使用何者是实现定义的</td>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::milli</a></span></td>
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<td><code>ms</code></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::centi</a></span></td>
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<td><code>cs</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::deci</a></span></td>
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<td><code>ds</code></td>
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<td><a href="cpp-numeric-ratio-ratio.html"><tt>std::ratio<1></tt></a></td>
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<td><code>s</code></td>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::deca</a></span></td>
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<td><code>das</code></td>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::hecto</a></span></td>
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<td><code>hs</code></td>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::kilo</a></span></td>
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<td><code>ks</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::mega</a></span></td>
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<td><code>Ms</code></td>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::giga</a></span></td>
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<td><code>Gs</code></td>
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</tr>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::tera</a></span></td>
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<td><code>Ts</code></td>
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</tr>
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::peta</a></span></td>
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<td><code>Ps</code></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::exa</a></span></td>
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<td><code>Es</code></td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-numeric-ratio-ratio.html"><tt>std::ratio<60></tt></a></td>
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<td><code>min</code></td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-numeric-ratio-ratio.html"><tt>std::ratio<3600></tt></a></td>
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<td><code>h</code></td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-numeric-ratio-ratio.html"><tt>std::ratio<86400></tt></a></td>
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<td><code>d</code></td>
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</tr>
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<td>非以上之一，且 <span class="t-c"><span class="mw-geshi cpp source-cpp">Period<span class="sy4">::</span><span class="me2">type</span><span class="sy4">::</span><span class="me2">den</span> <span class="sy1">==</span> <span class="nu0">1</span></span></span></td>
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<td><code>[<i>num</i>]s</code></td>
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</tr>
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<tr class="t-dsc">
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<td>非以上之一</td>
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<td><code>[<i>num</i>/<i>den</i>]s</code></td>
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</tr>
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</table>
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<p>对于表中最后二行，后缀中的 <code><i>num</i></code> 和 <code><i>den</i></code> 分别是格式化为不带前导零的 <code>Period::type::num</code> 和 <code>Period::type::den</code> 。</p>
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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>到流的引用，即 <code>os</code> 。</p>
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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-utility-format-format.html"><span class="t-lines"><span>format</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>在新 string 中存储参数的格式化表示<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-formatter.html"><span class="t-lines"><span>std::formatter<span class="t-dsc-small"><std::chrono::duration></span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td><span class="t-lc">std::formatter</span> 的特化，按提供的格式格式化 <code>duration</code><br />
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<span class="t-mark">(类模板特化)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string-operator_ltltgtgt.html"><span class="t-lines"><span>operator<<</span><span>operator>></span></span></a></div>
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</div>
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</td>
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<td>执行字符串的流输入与输出<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string-to_string.html"><span class="t-lines"><span>to_string</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>转换整数或浮点值为 <code>string</code><br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string-to_wstring.html"><span class="t-lines"><span>to_wstring</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>转换整数或浮点值为 <code>wstring</code><br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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