230 lines
14 KiB
HTML
230 lines
14 KiB
HTML
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<title>std::ostream_iterator</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_iterator_ostream_iterator 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>ostream_iterator</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-iterator.html">iterator</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-iterator.html"><iterator></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> T,<br /></span>
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<p> <span class="kw1">class</span> CharT <span class="sy1">=</span> <span class="kw4">char</span>,<br />
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<span class="kw1">class</span> Traits <span class="sy1">=</span> <a href="cpp-string-char_traits.html"><span class="kw1266">std::<span class="me2">char_traits</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span> <span class="sy1">></span><br />
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<span class="kw1">class</span> ostream_iterator <span class="sy4">:</span> <span class="kw1">public</span> <a href="cpp-iterator-iterator.html"><span class="kw657">std::<span class="me2">iterator</span></span></a><span class="sy1"><</span><a href="cpp-iterator-iterator_tags.html"><span class="kw653">std::<span class="me2">output_iterator_tag</span></span></a>,<br /></p>
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<span class="kw4">void</span>, <span class="kw4">void</span>, <span class="kw4">void</span>, <span class="kw4">void</span><span class="sy1">></span></div>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
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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> T,<br /></span>
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<p> <span class="kw1">class</span> CharT <span class="sy1">=</span> <span class="kw4">char</span>,<br />
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<span class="kw1">class</span> Traits <span class="sy1">=</span> <a href="cpp-string-char_traits.html"><span class="kw1266">std::<span class="me2">char_traits</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><br /></p>
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<span class="kw1">class</span> ostream_iterator<span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p><code>std::ostream_iterator</code> 是单趟<a href="cpp-named_req-OutputIterator.html"><span style="font-style:italic">老式输出迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyOutputIterator)</span></a> ，用 <code>operator<<</code> 写入相继 <code>T</code> 类型对象到为之创建迭代器的 <span class="t-lc"><a href="cpp-io-basic_ostream.html">std::basic_ostream</a></span> 对象。每次写操作后写入可选的分隔字符串。写操作在赋值给迭代器时（无论是否解引用）进行。自增 <code>std::ostream_iterator</code> 是无操作。</p>
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<p>典型实现中， <code>std::ostream_iterator</code> 仅有的数据成员是指向关联 <code>std::basic_ostream</code> 的指针和指向分隔字符串首字符的指针。</p>
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<p>写入字符时， <span class="t-lc"><a href="cpp-iterator-ostreambuf_iterator.html">std::ostreambuf_iterator</a></span> 更有效率，因为它避免对每个字符构造并析构一次 sentry 对象的开销。</p>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<td>成员类型</td>
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<td>定义</td>
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<td><code>iterator_category</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_tags.html"><span class="kw653">std::<span class="me2">output_iterator_tag</span></span></a></span></span></td>
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<td><code>value_type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span></td>
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<td><code>difference_type</code></td>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span></p>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a></span></span></p>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td><code>pointer</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span></td>
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<td><code>reference</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span></td>
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<td><code>char_type</code></td>
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<td><code>CharT</code></td>
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<td><code>traits_type</code></td>
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<td><code>Traits</code></td>
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<td><code>ostream_type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-io-basic_ostream.html"><span class="kw1714">std::<span class="me2">basic_ostream</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span></span></span></td>
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<p>要求通过从 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator.html"><span class="kw657">std::<span class="me2">iterator</span></span></a><span class="sy1"><</span><a href="cpp-iterator-iterator_tags.html"><span class="kw653">std::<span class="me2">output_iterator_tag</span></span></a>, <span class="kw4">void</span>, <span class="kw4">void</span>, <span class="kw4">void</span>, <span class="kw4">void</span><span class="sy1">></span></span></span> 继承获得成员类型 <code>iterator_category</code>、 <code>value_type</code>、 <code>difference_type</code>、 <code>pointer</code> 及 <code>reference</code> 。</p>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-iterator-ostream_iterator-ostream_iterator.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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<td>构造新的 ostream_iterator<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-iterator-ostream_iterator-~ostream_iterator.html"><span class="t-lines"><span>(析构函数)</span></span></a></div>
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</td>
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<td>析构 <code>ostream_iterator</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-iterator-ostream_iterator-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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<td>写对象到关联的输出序列<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-iterator-ostream_iterator-operator*.html"><span class="t-lines"><span>operator*</span></span></a></div>
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<td>无操作<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-iterator-ostream_iterator-operator_arith.html"><span class="t-lines"><span>operator++</span><span>operator++<span class="t-dsc-small">(int)</span></span></span></a></div>
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<td>无操作<br />
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<span class="t-mark">(公开成员函数)</span></td>
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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="t-example">
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<div class="t-example-live-link"></div>
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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"><span class="co2">#include <iostream></span>
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<span class="co2">#include <sstream></span>
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<span class="co2">#include <iterator></span>
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<span class="co2">#include <numeric></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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<a href="cpp-io-basic_istringstream.html"><span class="kw1734">std::<span class="me2">istringstream</span></span></a> str<span class="br0">(</span><span class="st0">"0.1 0.2 0.3 0.4"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-algorithm-partial_sum.html"><span class="kw1653">std::<span class="me2">partial_sum</span></span></a><span class="br0">(</span><a href="cpp-iterator-istream_iterator.html"><span class="kw668">std::<span class="me2">istream_iterator</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span>str<span class="br0">)</span>,
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<a href="cpp-iterator-istream_iterator.html"><span class="kw668">std::<span class="me2">istream_iterator</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span><span class="br0">)</span>,
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std<span class="sy4">::</span><span class="me2">ostream_iterator</span><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a>, <span class="st0">" "</span><span class="br0">)</span><span class="br0">)</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 dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">0.1 0.3 0.6 1</pre></div>
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</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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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-iterator-ostreambuf_iterator.html"><span class="t-lines"><span>ostreambuf_iterator</span></span></a></div>
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</div>
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</td>
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<td>写入 <span class="t-lc"><a href="cpp-io-basic_streambuf.html">std::basic_streambuf</a></span> 的输出迭代器<br />
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<span class="t-mark">(类模板)</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-iterator-istream_iterator.html"><span class="t-lines"><span>istream_iterator</span></span></a></div>
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</div>
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</td>
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<td>从 <span class="t-lc"><a href="cpp-io-basic_istream.html">std::basic_istream</a></span> 读取的输入迭代器<br />
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<span class="t-mark">(类模板)</span></td>
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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-experimental-ostream_joiner.html"><span class="t-lines"><span>std::experimental::ostream_joiner</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-libfund-ts-2 t-mark-ts">(库基础 TS v2)</span></span></span></div>
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</div>
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</td>
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<td>写入相继元素到输出流的输出迭代器，以分割器分隔相邻元素<br />
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<span class="t-mark">(类模板)</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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