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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>size, <span style="font-size:0.7em; line-height:130%">std::</span>ssize</h1>
<div id="bodyContent">
<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-array.html">&lt;array&gt;</a></code></div>
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<td></td>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-deque.html">&lt;deque&gt;</a></code></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>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-list.html">&lt;list&gt;</a></code></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-regex.html">&lt;regex&gt;</a></code></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-set.html">&lt;set&gt;</a></code></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-span.html">&lt;span&gt;</a></code></div>
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<div><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></div>
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<td>
<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-string.html">&lt;string&gt;</a></code></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-string_view.html">&lt;string_view&gt;</a></code></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-unordered_map.html">&lt;unordered_map&gt;</a></code></div>
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<td></td>
<td></td>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-unordered_set.html">&lt;unordered_set&gt;</a></code></div>
</td>
<td></td>
<td></td>
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<tr class="t-dsc-header">
<td>
<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-vector.html">&lt;vector&gt;</a></code></div>
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<td></td>
<td></td>
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<tr class="t-dcl t-since-cxx17">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> C<span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <span class="kw4">auto</span> size<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&amp;</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">&gt;</span> decltype<span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(1)</td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> C<span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <span class="kw4">auto</span> ssize<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&amp;</span> c<span class="br0">)</span><br />
&nbsp; &nbsp; <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="cpp-types-common_type.html"><span class="kw636">std::<span class="me2">common_type_t</span></span></a><span class="sy1">&lt;</span><a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a>,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <a href="cpp-types-make_signed.html"><span class="kw617">std::<span class="me2">make_signed_t</span></span></a><span class="sy1">&lt;</span>decltype<span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy1">&gt;&gt;</span><span class="sy4">;</span></div>
</td>
<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx17">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size<span class="br0">(</span><span class="kw4">const</span> T <span class="br0">(</span><span class="sy3">&amp;</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T, <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> N<span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> ssize<span class="br0">(</span><span class="kw4">const</span> T <span class="br0">(</span><span class="sy3">&amp;</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td>(4)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<p>&#36820;&#22238;&#32473;&#23450;&#33539;&#22260;&#30340;&#22823;&#23567;&#12290;</p>
<div class="t-li1"><span class="t-li">1-2)</span> &#36820;&#22238; <code>c.size()</code> &#65292;&#33509;&#38656;&#35201;&#21017;&#36716;&#25442;&#21040;&#36820;&#22238;&#31867;&#22411;&#12290;</div>
<div class="t-li1"><span class="t-li">3-4)</span> &#36820;&#22238; <code>N</code> &#12290;</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td>c</td>
<td>-</td>
<td>&#25317;&#26377; <code>size</code> &#25104;&#21592;&#20989;&#25968;&#30340;&#23481;&#22120;&#25110;&#35270;&#22270;</td>
</tr>
<tr class="t-par">
<td>array</td>
<td>-</td>
<td>&#20219;&#24847;&#31867;&#22411;&#30340;&#25968;&#32452;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p><code>c</code> &#25110; <code>array</code> &#30340;&#22823;&#23567;&#12290;</p>
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">&#24322;&#24120;</span></h3>
<div class="t-li1"><span class="t-li">1-2)</span> &#21487;&#33021;&#25243;&#20986;&#23454;&#29616;&#23450;&#20041;&#30340;&#24322;&#24120;&#12290;</div>
<h3><span class="mw-headline" id=".E9.87.8D.E8.BD.BD">&#37325;&#36733;</span></h3>
<p>&#21487;&#20197;&#20026;&#19981;&#26292;&#38706;&#36866;&#21512;&#30340; <code>size()</code> &#25104;&#21592;&#20989;&#25968;&#30340;&#31867;&#25110;&#26522;&#20030;&#25552;&#20379; <code>size</code> &#30340;&#33258;&#23450;&#20041;&#37325;&#36733;&#65292;&#20174;&#32780;&#33021;&#26816;&#27979;&#23427;&#12290;</p>
<table class="t-rev-begin">
<tr class="t-rev t-since-cxx20">
<td>
<p><a href="cpp-language-adl.html">&#23454;&#21442;&#20381;&#36182;&#26597;&#25214;</a>&#25152;&#25214;&#21040;&#30340; <code>size</code> &#37325;&#36733;&#33021;&#29992;&#20110;&#23450;&#21046; <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">size</span></span></span>&#12289; <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">ssize</span></span></span> &#21450; <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">empty</span></span></span> &#30340;&#34892;&#20026;&#12290;</p>
</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">&#21487;&#33021;&#30340;&#23454;&#29616;</span></h3>
<table class="eq-fun-cpp-table">
<tr>
<th>&#29256;&#26412;&#19968;</th>
</tr>
<tr>
<td>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> C<span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> <span class="kw4">auto</span> size<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&amp;</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">&gt;</span> decltype<span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">return</span> c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
</td>
</tr>
<tr>
<th>&#29256;&#26412;&#20108;</th>
</tr>
<tr>
<td>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> C<span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> <span class="kw4">auto</span> ssize<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&amp;</span> c<span class="br0">)</span>
<span class="sy2">-</span><span class="sy1">&gt;</span> <a href="cpp-types-common_type.html"><span class="kw636">std::<span class="me2">common_type_t</span></span></a><span class="sy1">&lt;</span><a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a>,
<a href="cpp-types-make_signed.html"><span class="kw617">std::<span class="me2">make_signed_t</span></span></a><span class="sy1">&lt;</span>decltype<span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy1">&gt;&gt;</span> <span class="br0">{</span>
<span class="kw1">using</span> R <span class="sy1">=</span> <a href="cpp-types-common_type.html"><span class="kw636">std::<span class="me2">common_type_t</span></span></a><span class="sy1">&lt;</span><a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a>,
<a href="cpp-types-make_signed.html"><span class="kw617">std::<span class="me2">make_signed_t</span></span></a><span class="sy1">&lt;</span>decltype<span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy1">&gt;&gt;</span><span class="sy4">;</span>
<span class="kw1">return</span> <span class="kw1">static_cast</span><span class="sy1">&lt;</span>R<span class="sy1">&gt;</span><span class="br0">(</span>c.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
</td>
</tr>
<tr>
<th>&#29256;&#26412;&#19977;</th>
</tr>
<tr>
<td>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size<span class="br0">(</span><span class="kw4">const</span> T <span class="br0">(</span><span class="sy3">&amp;</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="kw1">noexcept</span>
<span class="br0">{</span>
<span class="kw1">return</span> N<span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
</td>
</tr>
<tr>
<th>&#29256;&#26412;&#22235;</th>
</tr>
<tr>
<td>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T, <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> N<span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> ssize<span class="br0">(</span><span class="kw4">const</span> T <span class="br0">(</span><span class="sy3">&amp;</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="kw1">noexcept</span>
<span class="br0">{</span>
<span class="kw1">return</span> N<span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
</td>
</tr>
</table>
<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;vector&gt;</span>
<span class="co2">#include &lt;iterator&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-container-vector.html"><span class="kw1268">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v <span class="sy1">=</span> <span class="br0">{</span> <span class="nu0">3</span>, <span class="nu0">1</span>, <span class="nu0">4</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> std<span class="sy4">::</span><span class="me2">size</span><span class="br0">(</span>v<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw4">int</span> a<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span> <span class="sy2">-</span><span class="nu0">5</span>, <span class="nu0">10</span>, <span class="nu0">15</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> std<span class="sy4">::</span><span class="me2">size</span><span class="br0">(</span>a<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">3
3</pre></div>
</div>
</div>
<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-types-ptrdiff_t.html"><span class="t-lines"><span>ptrdiff_t</span></span></a></div>
</div>
</td>
<td>&#22312;&#20004;&#20010;&#25351;&#38024;&#30456;&#20943;&#26102;&#36820;&#22238;&#30340;&#26377;&#31526;&#21495;&#25972;&#25968;&#31867;&#22411;<br />
<span class="t-mark">(typedef)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-types-size_t.html"><span class="t-lines"><span>size_t</span></span></a></div>
</div>
</td>
<td><a href="cpp-language-sizeof.html"><tt>sizeof</tt></a> &#36816;&#31639;&#31526;&#36820;&#22238;&#30340;&#26080;&#31526;&#21495;&#25972;&#25968;&#31867;&#22411;<br />
<span class="t-mark">(typedef)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-ranges-size.html"><span class="t-lines"><span>ranges::size</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#36820;&#22238;&#31561;&#20110;&#33539;&#22260;&#22823;&#23567;&#30340;&#25972;&#25968;<br />
<span class="t-mark">(&#23450;&#21046;&#28857;&#23545;&#35937;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-ranges-ssize.html"><span class="t-lines"><span>ranges::ssize</span></span></a></div>
<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>&#36820;&#22238;&#31561;&#20110;&#33539;&#22260;&#22823;&#23567;&#30340;&#26377;&#31526;&#21495;&#25972;&#25968;<br />
<span class="t-mark">(&#23450;&#21046;&#28857;&#23545;&#35937;)</span></td>
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