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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>slice</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-numeric.html">numeric</a>&lrm; | <a href="cpp-numeric-valarray.html">valarray</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-valarray.html">&lt;valarray&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> slice<span class="sy4">;</span></span></div>
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<p><code>std::slice</code> &#26159;&#36873;&#25321;&#22120;&#31867;&#65292;&#26631;&#35782; <span class="t-lc"><a href="cpp-numeric-valarray.html">std::valarray</a></span> &#31867;&#20284;&#20110; <a href="https://en.wikipedia.org/wiki/BLAS" class="extiw" title="enwiki:BLAS">BLAS</a> &#30340;&#23376;&#38598;&#12290;&#19968;&#20010; <code>std::slice</code> &#31867;&#22411;&#30340;&#23545;&#35937;&#20445;&#26377;&#19977;&#20010;&#20540;&#65306;&#36215;&#22987;&#19979;&#26631;&#65292;&#36328;&#24230;&#65292;&#21450;&#23376;&#38598;&#20013;&#30340;&#20540;&#30340;&#24635;&#25968;&#12290; <code>std::slice</code> &#31867;&#22411;&#30340;&#23545;&#35937;&#21487;&#29992;&#20316; valarray &#30340; <code>operator[]</code> &#30340;&#19979;&#26631;&#12290;</p>
<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><strong class="selflink"><span class="t-lines"><span>(&#26500;&#36896;&#20989;&#25968;)</span></span></strong></div>
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<td>&#26500;&#36896;&#19968;&#20010; slice<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><strong class="selflink"><span class="t-lines"><span>start</span><span>size</span><span>stride</span></span></strong></div>
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<td>&#36820;&#22238; slice &#30340;&#21442;&#25968;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h2><span class="mw-headline" id="std::slice::slice"><span style="font-size:0.7em; line-height:130%">std::slice::</span>slice</span></h2>
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<div><span class="mw-geshi cpp source-cpp">slice<span class="br0">(</span><span class="br0">)</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">slice<span class="br0">(</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> start, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> stride <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp">slice<span class="br0">(</span> <span class="kw4">const</span> slice<span class="sy3">&amp;</span> other <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>&#26500;&#36896;&#19968;&#20010;&#26032;&#20999;&#29255;&#12290;</p>
<div class="t-li1"><span class="t-li">1)</span> &#40664;&#35748;&#26500;&#36896;&#20989;&#25968;&#12290;&#31561;&#20215;&#20110; <span class="t-c"><span class="mw-geshi cpp source-cpp">slice<span class="br0">(</span><span class="nu0">0</span>, <span class="nu0">0</span>, <span class="nu0">0</span><span class="br0">)</span></span></span> &#12290;&#27492;&#26500;&#36896;&#20989;&#25968;&#30340;&#23384;&#22312;&#21482;&#20026;&#20801;&#35768;&#26500;&#36896;&#25968;&#32452;&#30340;&#20999;&#29255;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#20197;&#21442;&#25968; <code>start</code> &#12289; <code>size</code> &#12289; <code>stride</code> &#26500;&#36896;&#26032;&#20999;&#29255;&#12290;&#27492;&#20999;&#29255;&#23558;&#24341;&#29992; <code>size</code> &#20010;&#20803;&#32032;&#65292;&#27599;&#20010;&#22788;&#20110;&#20301;&#32622;&#65306;</div>
<div class="t-li2"><span class="t-li"></span> <span class="texhtml" style="white-space: nowrap;">start + 0*stride</span></div>
<div class="t-li2"><span class="t-li"></span> <span class="texhtml" style="white-space: nowrap;">start + 1*stride</span></div>
<div class="t-li2"><span class="t-li"></span> <span class="texhtml" style="white-space: nowrap;">...</span></div>
<div class="t-li2"><span class="t-li"></span> <span class="texhtml" style="white-space: nowrap;">start + (size-1)*stride</span></div>
<div class="t-li1"><span class="t-li">3)</span> &#26500;&#36896; <code>other</code> &#30340;&#21103;&#26412;&#12290;</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
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<td>start</td>
<td>-</td>
<td>&#39318;&#20803;&#32032;&#30340;&#20301;&#32622;</td>
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<td>size</td>
<td>-</td>
<td>&#20999;&#29255;&#20013;&#30340;&#20803;&#32032;&#25968;</td>
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<td>stride</td>
<td>-</td>
<td>&#20999;&#29255;&#20013;&#21069;&#21518;&#20803;&#32032;&#30340;&#30456;&#23545;&#20301;&#32622;</td>
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<td>other</td>
<td>-</td>
<td>&#35201;&#22797;&#21046;&#30340;&#21478;&#19968;&#20999;&#29255;</td>
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<p><br /></p>
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<h2><span class="mw-headline" id="std::slice::start.2C_size.2C_stride"><span style="font-size:0.7em; line-height:130%">std::slice::</span>start, size, stride</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> start<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><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="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> stride<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<p>&#36820;&#22238;&#26500;&#36896;&#26102;&#20256;&#36882;&#32473;&#20999;&#29255;&#30340;&#21442;&#25968;&mdash;&mdash;&#20998;&#21035;&#20026;&#36215;&#28857;&#12289;&#22823;&#23567;&#21644;&#36328;&#24230;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0_2">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#20999;&#29255;&#30340;&#21442;&#25968;&mdash;&mdash;&#20998;&#21035;&#20026;&#36215;&#28857;&#12289;&#22823;&#23567;&#21644;&#36328;&#24230;&#12290;</p>
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">&#22797;&#26434;&#24230;</span></h3>
<p>&#24120;&#25968;&#12290;</p>
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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><strong class="selflink"><span class="t-lines"><span>operator==<span class="t-dsc-small">(std::slice)</span></span></span></strong></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>&#26816;&#26597;&#20108;&#20010;&#20999;&#29255;&#26159;&#21542;&#30456;&#31561;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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<h2><span class="mw-headline" id="operator.3D.3D.28std::slice.29">operator==<small>(std::slice)</small></span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">friend</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span> <span class="kw4">const</span> slice<span class="sy3">&amp;</span> lhs, <span class="kw4">const</span> slice<span class="sy3">&amp;</span> rhs <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<p>&#26816;&#26597; <code>lhs</code> &#19982; <code>rhs</code> &#30340;&#21442;&#25968;&mdash;&mdash;&#36215;&#28857;&#12289;&#22823;&#23567;&#21644;&#36328;&#24230;&#26159;&#21542;&#20998;&#21035;&#30456;&#31561;&#12290;</p>
<p>&#27492;&#20989;&#25968;&#23545;&#36890;&#24120;<a href="cpp-language-unqualified_lookup.html">&#26080;&#38480;&#23450;</a>&#25110;<a href="cpp-language-qualified_lookup.html">&#26377;&#38480;&#23450;&#26597;&#25214;</a>&#19981;&#21487;&#35265;&#65292;&#32780;&#21482;&#33021;&#22312; <code>std::slice</code> &#20026;&#21442;&#25968;&#30340;&#20851;&#32852;&#31867;&#26102;&#30001;<a href="cpp-language-adl.html">&#23454;&#21442;&#20381;&#36182;&#26597;&#25214;</a>&#25214;&#21040;&#12290;</p>
<p><code>!=</code> &#36816;&#31639;&#31526;&#20174; <code>operator==</code> <a href="cpp-language-operators.html#.E5.85.B3.E7.B3.BB.E8.BF.90.E7.AE.97.E7.AC.A6">&#21512;&#25104;</a>&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0_3">&#21442;&#25968;</span></h3>
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<td>lhs, rhs</td>
<td>-</td>
<td>&#35201;&#27604;&#36739;&#30340;&#20999;&#29255;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC_2">&#36820;&#22238;&#20540;</span></h3>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">lhs.<span class="me1">start</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> rhs.<span class="me1">start</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> lhs.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> rhs.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> lhs.<span class="me1">stride</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> rhs.<span class="me1">stride</span><span class="br0">(</span><span class="br0">)</span></span></span></p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<p>&#24314;&#31435;&#20110; valarray &#30340;&#24102;<a href="https://en.wikipedia.org/wiki/Trace_(linear_algebra)" class="extiw" title="enwiki:Trace (linear algebra)">&#36857;</a>&#35745;&#31639;&#20989;&#25968;&#30340;&#26497;&#31616;&#21270;&#30697;&#38453;&#31867;&#12290;</p>
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<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;valarray&gt;</span>
<span class="kw1">class</span> Matrix <span class="br0">{</span>
<a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> data<span class="sy4">;</span>
<span class="kw4">int</span> dim<span class="sy4">;</span>
<span class="kw1">public</span><span class="sy4">:</span>
Matrix<span class="br0">(</span><span class="kw4">int</span> r, <span class="kw4">int</span> c<span class="br0">)</span> <span class="sy4">:</span> data<span class="br0">(</span>r<span class="sy2">*</span>c<span class="br0">)</span>, dim<span class="br0">(</span>c<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
<span class="kw4">int</span><span class="sy3">&amp;</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> r, <span class="kw4">int</span> c<span class="br0">)</span> <span class="br0">{</span><span class="kw1">return</span> data<span class="br0">[</span>r<span class="sy2">*</span>dim <span class="sy2">+</span> c<span class="br0">]</span><span class="sy4">;</span><span class="br0">}</span>
<span class="kw4">int</span> trace<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
<span class="kw1">return</span> data<span class="br0">[</span>std<span class="sy4">::</span><span class="me2">slice</span><span class="br0">(</span><span class="nu0">0</span>, dim, dim<span class="sy2">+</span><span class="nu0">1</span><span class="br0">)</span><span class="br0">]</span>.<span class="me1">sum</span><span class="br0">(</span><span class="br0">)</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>
Matrix m<span class="br0">(</span><span class="nu0">3</span>,<span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">int</span> r<span class="sy1">=</span><span class="nu0">0</span><span class="sy4">;</span> r<span class="sy1">&lt;</span><span class="nu0">3</span><span class="sy4">;</span> <span class="sy2">++</span>r<span class="br0">)</span>
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">int</span> c<span class="sy1">=</span><span class="nu0">0</span><span class="sy4">;</span> c<span class="sy1">&lt;</span><span class="nu0">3</span><span class="sy4">;</span> <span class="sy2">++</span>c<span class="br0">)</span>
m<span class="br0">(</span>r, c<span class="br0">)</span> <span class="sy1">=</span> <span class="sy2">++</span>n<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;Trace of the matrix (1,2,3) (4,5,6) (7,8,9) is &quot;</span> <span class="sy1">&lt;&lt;</span> m.<span class="me1">trace</span><span class="br0">(</span><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>
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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">Trace of the matrix (1,2,3) (4,5,6) (7,8,9) is 15</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 class="t-dsc-member-div">
<div><a href="cpp-numeric-valarray-operator_at.html"><span class="t-lines"><span>operator[]</span></span></a></div>
</div>
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<td>&#33719;&#21462;/&#35774;&#32622; valarray &#25968;&#32452;&#20803;&#32032;&#12289;&#20999;&#29255;&#25110;&#25513;&#30721;<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-numeric-valarray-gslice.html"><span class="t-lines"><span>gslice</span></span></a></div>
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<td>valarray &#30340;&#36890;&#29992;&#20999;&#29255;&#65306;&#36215;&#22987;&#19979;&#26631;&#12289;&#38271;&#24230;&#38598;&#12289;&#27493;&#24133;&#38598;<br />
<span class="t-mark">(&#31867;)</span></td>
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<td>
<div class="t-dsc-member-div">
<div><a href="cpp-numeric-valarray-slice_array.html"><span class="t-lines"><span>slice_array</span></span></a></div>
</div>
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<td>&#21040; valarray &#24212;&#29992; slice &#21518;&#30340;&#23376;&#38598;&#30340;&#20195;&#29702;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
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