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<title>std::span&lt;T,Extent&gt;::operator=</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::span&lt;T,Extent&gt;::</span>operator=</h1>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> span<span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> span<span class="sy3">&amp;</span> other <span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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<p>&#36171;&#20540; <code>other</code> &#32473; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#12290;&#27492;&#40664;&#35748;&#21270;&#30340;&#36171;&#20540;&#36816;&#31639;&#31526;&#36827;&#34892;&#25968;&#25454;&#25351;&#38024;&#21644;&#22823;&#23567;&#30340;&#27973;&#22797;&#21046;&#65292;&#21363;&#35843;&#29992;&#27492;&#20989;&#25968;&#21518;&#65292; <span class="t-c"><span class="mw-geshi cpp source-cpp">data<span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> other.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span></span></span> &#19988; <span class="t-c"><span class="mw-geshi cpp source-cpp">size<span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> other.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>other</td>
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<td>&#35201;&#22797;&#21046;&#30340;&#21478;&#19968; span</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#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;algorithm&gt;</span>
<span class="co2">#include &lt;array&gt;</span>
<span class="co2">#include &lt;cassert&gt;</span>
<span class="co2">#include &lt;cstddef&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;span&gt;</span>
<span class="co2">#include &lt;string_view&gt;</span>
<span class="kw4">void</span> print<span class="br0">(</span><a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a> info <span class="sy1">=</span> <span class="st0">&quot;&quot;</span>, std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">const</span> <span class="kw4">int</span><span class="sy1">&gt;</span> span <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>,
<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> extent <span class="sy1">=</span> <span class="nu0">0</span>, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size_of <span class="sy1">=</span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">if</span> <span class="br0">(</span>span.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> info <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw1">return</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> info <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;[&#39;</span> <span class="sy1">&lt;&lt;</span> span.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;] {&quot;</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">for_each</span><span class="br0">(</span>span, <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> x<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> x<span class="sy4">;</span> <span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; }&quot;</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>extent <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; extent = &quot;</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>extent <span class="sy1">==</span> std<span class="sy4">::</span><span class="me2">dynamic_extent</span><span class="br0">)</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;dynamic&quot;</span><span class="sy4">;</span>
<span class="kw1">else</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> extent<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">if</span> <span class="br0">(</span>size_of <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;, sizeof = &quot;</span> <span class="sy1">&lt;&lt;</span> size_of<span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <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>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>,<span class="nu0">6</span><span class="sy1">&gt;</span> a1<span class="sy4">;</span>
<a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>,<span class="nu0">6</span><span class="sy1">&gt;</span> a2<span class="sy4">;</span>
a1.<span class="me1">fill</span><span class="br0">(</span><span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
a2.<span class="me1">fill</span><span class="br0">(</span><span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">auto</span> s1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">span</span><span class="br0">(</span>a1<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">auto</span> s2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">span</span><span class="br0">(</span>a2<span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;s1&quot;</span>, s1, s1.<span class="me1">extent</span>, sizeof<span class="br0">(</span>s1<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;s2&quot;</span>, s2, s2.<span class="me1">extent</span>, sizeof<span class="br0">(</span>s2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// &#26816;&#26597;&#36171;&#20540;&#26159;&#21542;&#36827;&#34892;&#27973;&#22797;&#21046;</span>
s1 <span class="sy1">=</span> s2<span class="sy4">;</span>
<span class="br0">(</span>s1.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> s2.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> s1.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> s2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
<span class="sy4">?</span> print<span class="br0">(</span><span class="st0">&quot;s1 = s2; is a shallow copy!&quot;</span><span class="br0">)</span>
<span class="sy4">:</span> print<span class="br0">(</span><span class="st0">&quot;s1 = s2; is a deep copy!&quot;</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;s1&quot;</span>, s1<span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;Fill s1 with 5:&quot;</span><span class="br0">)</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">fill</span><span class="br0">(</span>s1, <span class="nu0">5</span><span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// s2 &#20134;&#34987;&ldquo;&#26356;&#26032;&rdquo;&#22240;&#20026; s1 &#19982; s2 &#24341;&#29992;&#21516;&#19968;&#25968;&#25454;</span>
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">equal</span><span class="br0">(</span>s1, s2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;s1&quot;</span>, s1<span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;s2&quot;</span>, s2<span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">int</span> a3<span class="br0">[</span><span class="br0">]</span> <span class="br0">{</span><span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">int</span> a4<span class="br0">[</span><span class="br0">]</span> <span class="br0">{</span><span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">int</span> a5<span class="br0">[</span><span class="br0">]</span> <span class="br0">{</span><span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">int</span>, std<span class="sy4">::</span><span class="me2">dynamic_extent</span><span class="sy1">&gt;</span> dynamic_1 <span class="br0">{</span>a3<span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">int</span>, std<span class="sy4">::</span><span class="me2">dynamic_extent</span><span class="sy1">&gt;</span> dynamic_2 <span class="br0">{</span>a4, <span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="nu0">4</span><span class="sy1">&gt;</span> static_1 <span class="br0">{</span>a3<span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="nu0">4</span><span class="sy1">&gt;</span> static_2 <span class="br0">{</span>a4<span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">span</span><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="nu0">3</span><span class="sy1">&gt;</span> static_3 <span class="br0">{</span>a5<span class="br0">}</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;dynamic_1&quot;</span>, dynamic_1, dynamic_1.<span class="me1">extent</span>, sizeof<span class="br0">(</span>dynamic_1<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;dynamic_2&quot;</span>, dynamic_2, dynamic_2.<span class="me1">extent</span>, sizeof<span class="br0">(</span>dynamic_2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;static_1&quot;</span>, static_1, static_1.<span class="me1">extent</span>, sizeof<span class="br0">(</span>static_1<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;static_2&quot;</span>, static_2, static_2.<span class="me1">extent</span>, sizeof<span class="br0">(</span>static_2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
print<span class="br0">(</span><span class="st0">&quot;static_3&quot;</span>, static_3, static_3.<span class="me1">extent</span>, sizeof<span class="br0">(</span>static_3<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
dynamic_1 <span class="sy1">=</span> dynamic_2<span class="sy4">;</span> <span class="co1">// OK</span>
dynamic_1 <span class="sy1">=</span> static_1<span class="sy4">;</span> <span class="co1">// OK</span>
<span class="co1">// static_1 = dynamic_1; // &#38169;&#35823;&#65306;&#26080;&#21305;&#37197;&#30340; &lsquo;operator=&rsquo;</span>
static_1 <span class="sy1">=</span> static_2<span class="sy4">;</span> <span class="co1">// OK &#65306;&#30456;&#21516;&#38271;&#24230; = 4</span>
<span class="co1">// static_1 = static_3; // &#38169;&#35823;&#65306;&#19981;&#21516;&#38271;&#24230;&#65306; 4 &#19982; 3</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">s1[6] { 3 3 3 3 3 3 } extent = 6, sizeof = 8
s2[6] { 4 4 4 4 4 4 } extent = 6, sizeof = 8
s1 = s2; is a shallow copy!
s1[6] { 4 4 4 4 4 4 }
Fill s1 with 5:
s1[6] { 5 5 5 5 5 5 }
s2[6] { 5 5 5 5 5 5 }
dynamic_1[4] { 1 2 3 4 } extent = dynamic, sizeof = 16
dynamic_2[3] { 2 3 4 } extent = dynamic, sizeof = 16
static_1[4] { 1 2 3 4 } extent = 4, sizeof = 8
static_2[4] { 2 3 4 5 } extent = 4, sizeof = 8
static_3[3] { 3 4 5 } extent = 3, sizeof = 8</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-container-span-span.html"><span class="t-lines"><span>(&#26500;&#36896;&#20989;&#25968;)</span></span></a></div>
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<td>&#26500;&#36896; <code>span</code><br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><a href="cpp-container-span-data.html"><span class="t-lines"><span>data</span></span></a></div>
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<td>&#36820;&#22238;&#25351;&#21521;&#20803;&#32032;&#24207;&#21015;&#36215;&#22987;&#30340;&#25351;&#38024;<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-container-span-size.html"><span class="t-lines"><span>size</span></span></a></div>
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<td>&#36820;&#22238;&#24207;&#21015;&#20013;&#30340;&#20803;&#32032;&#25968;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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