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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>piecewise_construct</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-utility.html">&lt;utility&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <a href="cpp-utility-piecewise_construct_t.html"><span class="kw1105">std::<span class="me2">piecewise_construct_t</span></span></a> piecewise_construct<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<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">inline</span> <span class="kw4">constexpr</span> <a href="cpp-utility-piecewise_construct_t.html"><span class="kw1105">std::<span class="me2">piecewise_construct_t</span></span></a> piecewise_construct<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#24120;&#37327; <code>std::piecewise_construct</code> &#26159;&#31354;&#30340;&#32467;&#26500;&#20307;&#26631;&#31614;&#31867;&#22411; <span class="t-lc"><a href="cpp-utility-piecewise_construct_t.html">std::piecewise_construct_t</a></span> &#30340;&#23454;&#20363;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;utility&gt;</span>
<span class="co2">#include &lt;tuple&gt;</span>
<span class="kw1">struct</span> Foo <span class="br0">{</span>
Foo<span class="br0">(</span><a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="kw4">float</span><span class="sy1">&gt;</span><span class="br0">)</span>
<span class="br0">{</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;Constructed a Foo from a tuple<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
Foo<span class="br0">(</span><span class="kw4">int</span>, <span class="kw4">float</span><span class="br0">)</span>
<span class="br0">{</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;Constructed a Foo from an int and a float<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="kw4">float</span><span class="sy1">&gt;</span> t<span class="br0">(</span><span class="nu0">1</span>, <span class="nu16">3.14</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1">&lt;</span>Foo, Foo<span class="sy1">&gt;</span> p1<span class="br0">(</span>t, t<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1">&lt;</span>Foo, Foo<span class="sy1">&gt;</span> p2<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">piecewise_construct</span>, t, t<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">Constructed a Foo from a tuple
Constructed a Foo from a tuple
Constructed a Foo from an int and a float
Constructed a Foo from an int and a float</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-utility-piecewise_construct_t.html"><span class="t-lines"><span>piecewise_construct_t</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#29992;&#20110;&#20026;&#36880;&#27573;&#26500;&#36896;&#36873;&#25321;&#27491;&#30830;&#20989;&#25968;&#37325;&#36733;&#30340;&#26631;&#31614;&#31867;&#22411;<br />
<span class="t-mark">(&#31867;)</span></td>
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<div><a href="cpp-utility-pair-pair.html"><span class="t-lines"><span>(&#26500;&#36896;&#20989;&#25968;)</span></span></a></div>
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<td>&#26500;&#36896;&#26032;&#30340; pair<br />
<span class="t-mark">(<code>std::pair&lt;T1,T2&gt;</code> &#30340;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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