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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>istream_iterator</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-iterator.html">iterator</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-iterator.html">&lt;iterator&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T,<br /></span>
<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="kw1">class</span> CharT <span class="sy1">=</span> <span class="kw4">char</span>,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <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">&lt;</span>CharT<span class="sy1">&gt;</span>,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="kw1">class</span> Distance <span class="sy1">=</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> <span class="sy1">&gt;</span><br />
<span class="kw1">class</span> istream_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">&lt;</span><a href="cpp-iterator-iterator_tags.html"><span class="kw652">std::<span class="me2">input_iterator_tag</span></span></a>,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;T, Distance, <span class="kw4">const</span> T<span class="sy2">*</span>, <span class="kw4">const</span> T<span class="sy3">&amp;</span><span class="sy1">&gt;</span></div>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T,<br /></span>
<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="kw1">class</span> CharT <span class="sy1">=</span> <span class="kw4">char</span>,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <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">&lt;</span>CharT<span class="sy1">&gt;</span>,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="kw1">class</span> Distance <span class="sy1">=</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> <span class="sy1">&gt;</span><br /></p>
<span class="kw1">class</span> istream_iterator<span class="sy4">;</span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p><code>std::istream_iterator</code> &#26159;&#21333;&#36255;&#36755;&#20837;&#36845;&#20195;&#22120;&#65292;&#20174;&#20026;&#20043;&#21019;&#24314;&#36845;&#20195;&#22120;&#30340; <span class="t-lc"><a href="cpp-io-basic_istream.html">std::basic_istream</a></span> &#23545;&#35937;&#35835;&#21462; <code>T</code> &#31867;&#22411;&#30340;&#30456;&#32487;&#23545;&#35937;&#65292;&#36890;&#36807;&#35843;&#29992;&#36866;&#24403;&#30340; <code>operator&gt;&gt;</code> &#12290;&#23454;&#38469;&#35835;&#21462;&#25805;&#20316;&#22312;&#33258;&#22686;&#65292;&#32780;&#38750;&#35299;&#24341;&#29992;&#36845;&#20195;&#22120;&#26102;&#36827;&#34892;&#12290;&#22312;&#26500;&#36896;&#36845;&#20195;&#22120;&#26102;&#35835;&#21462;&#39318;&#20010;&#23545;&#35937;&#12290;&#35299;&#24341;&#29992;&#21482;&#36820;&#22238;&#26368;&#36817;&#35835;&#21462;&#30340;&#23545;&#35937;&#30340;&#21103;&#26412;&#12290;</p>
<p>&#40664;&#35748;&#26500;&#36896;&#30340; <code>std::istream_iterator</code> &#34987;&#31216;&#20026;<i>&#27969;&#23614;</i>&#36845;&#20195;&#22120;&#12290;&#21512;&#27861;&#30340; <code>std::istream_iterator</code> &#25269;&#36798;&#24213;&#23618;&#27969;&#23614;&#26102;&#65292;&#23427;&#21464;&#24471;&#31561;&#20110;&#27969;&#23614;&#36845;&#20195;&#22120;&#12290;&#35299;&#24341;&#29992;&#21644;&#36827;&#19968;&#27493;&#33258;&#22686;&#23427;&#23548;&#33268;&#26410;&#23450;&#20041;&#34892;&#20026;&#12290;</p>
<p><code>std::istream_iterator</code> &#30340;&#20856;&#22411;&#23454;&#29616;&#20445;&#26377;&#20108;&#20010;&#25968;&#25454;&#25104;&#21592;&#65306;&#25351;&#21521;&#20851;&#32852; <span class="t-lc"><a href="cpp-io-basic_istream.html">std::basic_istream</a></span> &#23545;&#35937;&#30340;&#25351;&#38024;&#21644;&#26368;&#36817;&#35835;&#21462;&#30340; <code>T</code> &#31867;&#22411;&#20540;&#12290;</p>
<p><code>T</code> &#24517;&#39035;&#28385;&#36275;<a href="cpp-named_req-DefaultConstructible.html"><span style="font-style:italic">&#21487;&#40664;&#35748;&#26500;&#36896;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(DefaultConstructible)</span></a> &#12289;<a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">&#21487;&#22797;&#21046;&#26500;&#36896;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(CopyConstructible)</span></a> &#21644;<a href="cpp-named_req-CopyAssignable.html"><span style="font-style:italic">&#21487;&#22797;&#21046;&#36171;&#20540;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(CopyAssignable)</span></a> &#35201;&#27714;&#12290;</p>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">&#25104;&#21592;&#31867;&#22411;</span></h3>
<table class="t-dsc-begin">
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<td>&#25104;&#21592;&#31867;&#22411;</td>
<td>&#23450;&#20041;</td>
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<td><code>iterator_category</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_tags.html"><span class="kw652">std::<span class="me2">input_iterator_tag</span></span></a></span></span></td>
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<td><code>value_type</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">T</span></span></td>
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<td><code>difference_type</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">Distance</span></span></td>
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<td><code>pointer</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> T<span class="sy2">*</span></span></span></td>
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<tr class="t-dsc">
<td><code>reference</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> T<span class="sy3">&amp;</span></span></span></td>
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<td><code>char_type</code></td>
<td><code>CharT</code></td>
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<td><code>traits_type</code></td>
<td><code>Traits</code></td>
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<td><code>istream_type</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-io-basic_istream.html"><span class="kw1712">std::<span class="me2">basic_istream</span></span></a><span class="sy1">&lt;</span>CharT, Traits<span class="sy1">&gt;</span></span></span></td>
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<p>&#35201;&#27714;&#36890;&#36807;&#20174; <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">&lt;</span><a href="cpp-iterator-iterator_tags.html"><span class="kw652">std::<span class="me2">input_iterator_tag</span></span></a>, T, Distance, <span class="kw4">const</span> T<span class="sy2">*</span>, <span class="kw4">const</span> T<span class="sy3">&amp;</span><span class="sy1">&gt;</span></span></span> &#32487;&#25215;&#33719;&#24471;&#25104;&#21592;&#31867;&#22411; <code>iterator_category</code>&#12289; <code>value_type</code>&#12289; <code>difference_type</code>&#12289; <code>pointer</code> &#21450; <code>reference</code> &#12290;</p>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 &#21069;)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
<div><a href="cpp-iterator-istream_iterator-istream_iterator.html"><span class="t-lines"><span>(&#26500;&#36896;&#20989;&#25968;)</span></span></a></div>
</div>
</td>
<td>&#26500;&#36896;&#26032;&#30340; istream_iterator<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
<div><a href="cpp-iterator-istream_iterator-~istream_iterator.html"><span class="t-lines"><span>(&#26512;&#26500;&#20989;&#25968;)</span></span></a></div>
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<td>&#26512;&#26500; istream_iterator &#65292;&#21253;&#21547;&#32531;&#20914;&#30340;&#20540;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
<div><a href="cpp-iterator-istream_iterator-operator*.html"><span class="t-lines"><span>operator*</span><span>operator-&gt;</span></span></a></div>
</div>
</td>
<td>&#36820;&#22238;&#24403;&#21069;&#20803;&#32032;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-iterator-istream_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>&#25512;&#36827;&#36845;&#20195;&#22120;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">&#38750;&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div class="t-dsc-member-div">
<div><a href="cpp-iterator-istream_iterator-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator!=</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 &#20013;&#31227;&#38500;)</span></span></span></div>
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<td>&#27604;&#36739;&#20004;&#20010; <code>istream_iterator</code><br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#35835;&#23383;&#31526;&#26102;&#65292; <code>std::istream_iterator</code> &#40664;&#35748;&#36339;&#36807;&#31354;&#30333;&#31526;&#65288;&#38500;&#38750;&#29992; <span class="t-lc"><a href="cpp-io-manip-skipws.html">std::noskipws</a></span> &#25110;&#31561;&#20215;&#29289;&#31105;&#29992;&#65292;&#32780; <span class="t-lc"><a href="cpp-iterator-istreambuf_iterator.html">std::istreambuf_iterator</a></span> &#19981;&#36339;&#36807;&#12290;&#21478;&#22806;&#65292; <span class="t-lc"><a href="cpp-iterator-istreambuf_iterator.html">std::istreambuf_iterator</a></span> &#26356;&#26377;&#25928;&#29575;&#65292;&#22240;&#20026;&#23427;&#36991;&#20813;&#23545;&#27599;&#20010;&#23383;&#31526;&#26500;&#36896;&#24182;&#26512;&#26500;&#19968;&#27425; sentry &#23545;&#35937;&#30340;&#24320;&#38144;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<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 &lt;iostream&gt;</span>
<span class="co2">#include &lt;sstream&gt;</span>
<span class="co2">#include &lt;iterator&gt;</span>
<span class="co2">#include &lt;numeric&gt;</span>
<span class="co2">#include &lt;algorithm&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<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">&quot;0.1 0.2 0.3 0.4&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-algorithm-partial_sum.html"><span class="kw1653">std::<span class="me2">partial_sum</span></span></a><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">istream_iterator</span><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span><span class="br0">(</span>str<span class="br0">)</span>,
std<span class="sy4">::</span><span class="me2">istream_iterator</span><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="br0">)</span>,
<a href="cpp-iterator-ostream_iterator.html"><span class="kw669">std::<span class="me2">ostream_iterator</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</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">&quot; &quot;</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-basic_istringstream.html"><span class="kw1734">std::<span class="me2">istringstream</span></span></a> str2<span class="br0">(</span><span class="st0">&quot;1 3 5 7 8 9 10&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;<span class="es1">\n</span>The first even number is &quot;</span> <span class="sy1">&lt;&lt;</span>
<span class="sy2">*</span><a href="cpp-algorithm-find_if_not.html"><span class="kw1574">std::<span class="me2">find_if</span></span></a><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">istream_iterator</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span>str2<span class="br0">)</span>,
std<span class="sy4">::</span><span class="me2">istream_iterator</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="br0">)</span>,
<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">int</span> i<span class="br0">)</span><span class="br0">{</span> <span class="kw1">return</span> i <span class="sy2">%</span> <span class="nu0">2</span> <span class="sy1">==</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;.<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="co1">// &quot; 9 10&quot; &#30041;&#22312;&#27969;&#20013;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">0.1 0.3 0.6 1
The first even number is 8.</pre></div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">&#32570;&#38519;&#25253;&#21578;</span></h3>
<p>&#19979;&#21015;&#26356;&#25913;&#34892;&#20026;&#30340;&#32570;&#38519;&#25253;&#21578;&#36861;&#28335;&#22320;&#24212;&#29992;&#20110;&#20197;&#21069;&#20986;&#29256;&#30340; C++ &#26631;&#20934;&#12290;</p>
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<tr>
<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
</tr>
<tr>
<td><a rel="nofollow" class="external text" href="https://wg21.link/P0738R2">P0738R2</a></td>
<td>C++98</td>
<td>&#39318;&#27425;&#35835;&#21462;&#21487;&#20197;&#24310;&#36831;&#21040;&#39318;&#27425;&#35299;&#24341;&#29992;</td>
<td>&#39318;&#27425;&#35835;&#21462;&#22312;&#26500;&#36896;&#20989;&#25968;&#20013;&#36827;&#34892;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-iterator-ostream_iterator.html"><span class="t-lines"><span>ostream_iterator</span></span></a></div>
</div>
</td>
<td>&#20889;&#20837; <span class="t-lc"><a href="cpp-io-basic_ostream.html">std::basic_ostream</a></span> &#30340;&#36755;&#20986;&#36845;&#20195;&#22120;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-iterator-istreambuf_iterator.html"><span class="t-lines"><span>istreambuf_iterator</span></span></a></div>
</div>
</td>
<td>&#20174; <span class="t-lc"><a href="cpp-io-basic_streambuf.html">std::basic_streambuf</a></span> &#35835;&#21462;&#30340;&#36755;&#20837;&#36845;&#20195;&#22120;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
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</div>
<div class="visualClear"></div>
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