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<title>std::round, std::roundf, std::roundl, std::lround, std::lroundf, std::lroundl, std::llround, std::llroundf</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>round, <span style="font-size:0.7em; line-height:130%">std::</span>roundf, <span style="font-size:0.7em; line-height:130%">std::</span>roundl, <span style="font-size:0.7em; line-height:130%">std::</span>lround, <span style="font-size:0.7em; line-height:130%">std::</span>lroundf, <span style="font-size:0.7em; line-height:130%">std::</span>lroundl, <span style="font-size:0.7em; line-height:130%">std::</span>llround, <span style="font-size:0.7em; line-height:130%">std::</span>llroundf</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-math.html">math</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-cmath.html">&lt;cmath&gt;</a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span> &nbsp; &nbsp; &nbsp; round <span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">float</span> &nbsp; &nbsp; &nbsp; roundf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(1)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span> &nbsp; &nbsp; &nbsp;round <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span> round <span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> <span class="kw4">double</span> roundl<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span> &nbsp; &nbsp; &nbsp;round <span class="br0">(</span> IntegralType arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(4)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lround <span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> lroundf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(5)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lround <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(6)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lround <span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> lroundl<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(7)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lround <span class="br0">(</span> IntegralType arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(8)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span> llround <span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> <span class="kw4">long</span> llroundf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(9)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span> llround <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(10)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span> llround <span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> <span class="kw4">long</span> llroundl<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(11)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span> llround <span class="br0">(</span> IntegralType arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(12)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div class="t-li1"><span class="t-li">1-3)</span> &#35745;&#31639; <code>arg</code> &#30340;&#26368;&#25509;&#36817;&#25972;&#25968;&#20540;&#65288;&#20197;&#28014;&#28857;&#26684;&#24335;&#65289;&#65292;&#20013;&#28857;&#24773;&#20917;&#33293;&#20837;&#20026;&#36828;&#31163;&#38646;&#65292;&#26080;&#20851;&#20046;&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;&#12290;</div>
<div class="t-li1"><span class="t-li">5-7, 9-11)</span> &#35745;&#31639; <code>arg</code> &#30340;&#26368;&#25509;&#36817;&#25972;&#25968;&#20540;&#65288;&#20197;&#25972;&#25968;&#26684;&#24335;&#65289;&#65292;&#20013;&#28857;&#24773;&#20917;&#33293;&#20837;&#20026;&#36828;&#31163;&#38646;&#65292;&#26080;&#20851;&#20046;&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;&#12290;</div>
<div class="t-li1"><span class="t-li">4,8,12)</span> &#25509;&#21463;&#20219;&#20309;<a href="cpp-types-is_integral.html">&#25972;&#25968;&#31867;&#22411;</a>&#21442;&#25968;&#30340;&#37325;&#36733;&#38598;&#25110;&#20989;&#25968;&#27169;&#26495;&#12290;&#20998;&#21035;&#31561;&#20215;&#20110; 2) &#12289; 6) &#25110; 10) &#65288;&#23558;&#21442;&#25968;&#36716;&#22411;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> &#65289;&#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>arg</td>
<td>-</td>
<td>&#28014;&#28857;&#20540;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#33509;&#19981;&#20986;&#29616;&#38169;&#35823;&#65292;&#21017;&#36820;&#22238; <code>arg</code> &#30340;&#26368;&#25509;&#36817;&#25972;&#25968;&#20540;&#65292;&#20013;&#28857;&#24773;&#20917;&#20026;&#36828;&#31163;&#38646;&#32773;&#12290;</p>
<div class="t-plot">
<div class="t-plot-left">&#36820;&#22238;&#20540;</div>
<div class="t-plot-image-left"><img alt="math-round away zero.svg" src="math-round_away_zero.svg" width="200" height="200" /></div>
<div class="t-plot-bottom">&#21442;&#25968;</div>
</div>
<p>&#33509;&#20986;&#29616;&#23450;&#20041;&#22495;&#38169;&#35823;&#65292;&#21017;&#36820;&#22238;&#23454;&#29616;&#23450;&#20041;&#20540;&#12290;</p>
<h3><span class="mw-headline" id=".E9.94.99.E8.AF.AF.E5.A4.84.E7.90.86">&#38169;&#35823;&#22788;&#29702;</span></h3>
<p>&#25253;&#21578; <span class="t-lc"><a href="cpp-numeric-math-math_errhandling.html">math_errhandling</a></span> &#20013;&#25351;&#23450;&#30340;&#38169;&#35823;&#12290;</p>
<p>&#33509; <code>std::lround</code> &#25110; <code>std::llround</code> &#30340;&#32467;&#26524;&#22312;&#36820;&#22238;&#31867;&#22411;&#30340;&#21487;&#34920;&#31034;&#33539;&#22260;&#22806;&#65292;&#21017;&#21487;&#33021;&#20986;&#29616;&#23450;&#20041;&#22495;&#38169;&#35823;&#25110;&#20540;&#22495;&#38169;&#35823;&#12290;</p>
<p>&#33509;&#23454;&#29616;&#25903;&#25345; IEEE &#28014;&#28857;&#31639;&#26415;&#65288; IEC 60559 &#65289;&#65292;&#21017;</p>
<dl>
<dd>&#23545;&#20110; <code>std::round</code> &#20989;&#25968;&#65306;</dd>
</dl>
<ul>
<li>&#24403;&#21069;<a href="cpp-numeric-fenv-FE_round.html">&#33293;&#20837;&#27169;&#24335;</a>&#26080;&#25928;&#12290;</li>
<li>&#33509; <code>arg</code> &#20026; &plusmn;&infin; &#65292;&#21017;&#36820;&#22238;&#19981;&#20462;&#25913;&#30340;&#21442;&#25968;&#12290;</li>
<li>&#33509; <code>arg</code> &#20026; &plusmn;0 &#65292;&#21017;&#36820;&#22238;&#19981;&#20462;&#25913;&#30340;&#21442;&#25968;&#12290;</li>
<li>&#33509; <code>arg</code> &#20026; NaN &#65292;&#21017;&#36820;&#22238; NaN &#12290;</li>
</ul>
<dl>
<dd>&#23545;&#20110; <code>std::lround</code> &#21644; <code>std::llround</code> &#20989;&#25968;&#65306;</dd>
</dl>
<ul>
<li>&#20915;&#19981;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INEXACT</a></span> &#12290;</li>
<li>&#24403;&#21069;<a href="cpp-numeric-fenv-FE_round.html">&#33293;&#20837;&#27169;&#24335;</a>&#26080;&#25928;&#12290;</li>
<li>&#33509; <code>arg</code> &#20026; &plusmn;&infin; &#65292;&#21017;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INVALID</a></span> &#24182;&#36820;&#22238;&#23454;&#29616;&#23450;&#20041;&#20540;&#12290;</li>
<li>&#33509;&#33293;&#20837;&#32467;&#26524;&#22312;&#36820;&#22238;&#31867;&#22411;&#33539;&#22260;&#22806;&#65292;&#21017;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INVALID</a></span> &#24182;&#36820;&#22238;&#23454;&#29616;&#23450;&#20041;&#20540;&#12290;</li>
<li>&#33509; <code>arg</code> &#20026; NaN &#65292;&#21017;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INVALID</a></span> &#24182;&#36820;&#22238;&#23454;&#29616;&#23450;&#20041;&#20540;&#12290;</li>
</ul>
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">&#27880;&#24847;</span></h3>
<p>&#33293;&#20837;&#38750;&#25972;&#25968;&#26377;&#38480;&#20540;&#26102; <code>std::round</code> &#21487;&#20197;&#65288;&#20294;&#19981;&#35201;&#27714;&#65289;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INEXACT</a></span> &#12290;</p>
<p>&#25152;&#26377;&#26631;&#20934;&#28014;&#28857;&#26684;&#24335;&#20013;&#65292;&#26368;&#22823;&#21487;&#34920;&#31034;&#28014;&#28857;&#20540;&#22343;&#20026;&#20934;&#30830;&#30340;&#25972;&#25968;&#65292;&#25925; <code>std::round</code> &#33258;&#36523;&#20915;&#19981;&#19978;&#28322;&#65307;&#28982;&#32780;&#22312;&#23384;&#20648;&#20110;&#25972;&#25968;&#23545;&#35937;&#26102;&#65292;&#32467;&#26524;&#21487;&#33021;&#28322;&#20986;&#20219;&#20309;&#25972;&#25968;&#31867;&#22411;&#65288;&#21253;&#21547; <span class="t-lc"><a href="cpp-types-integer.html">std::intmax_t</a></span> &#65289;&#12290;</p>
<p><a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/lround.html">POSIX &#25351;&#23450;</a> <code>std::lround</code> &#25110; <code>std::llround</code> &#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INEXACT</a></span> &#30340;&#25152;&#26377;&#24773;&#20917;&#37117;&#26159;&#23450;&#20041;&#22495;&#38169;&#35823;&#12290;</p>
<p><code>std::round</code> &#30340; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> &#29256;&#26412;&#34920;&#29616;&#20026;&#22914;&#21516;&#23454;&#29616;&#22914;&#19979;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;cmath&gt;</span>
<span class="co2">#include &lt;cfenv&gt;</span>
<span class="co2">#pragma STDC FENV_ACCESS ON</span>
<span class="kw4">double</span> round<span class="br0">(</span><span class="kw4">double</span> x<span class="br0">)</span>
<span class="br0">{</span>
std<span class="sy4">::</span><span class="me2">fenv_t</span> save_env<span class="sy4">;</span>
<a href="cpp-numeric-fenv-feholdexcept.html"><span class="kw1456">std::<span class="me2">feholdexcept</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>save_env<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">double</span> result <span class="sy1">=</span> <a href="cpp-numeric-math-rint.html"><span class="kw1354">std::<span class="me2">rint</span></span></a><span class="br0">(</span>x<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span><a href="cpp-numeric-fenv-fetestexcept.html"><span class="kw1448">std::<span class="me2">fetestexcept</span></span></a><span class="br0">(</span><a href="cpp-numeric-fenv-FE_exceptions.html"><span class="kw1460">FE_INEXACT</span></a><span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
<span class="kw4">auto</span> <span class="kw4">const</span> save_round <span class="sy1">=</span> <a href="cpp-numeric-fenv-feround.html"><span class="kw1452">std::<span class="me2">fegetround</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-numeric-fenv-feround.html"><span class="kw1453">std::<span class="me2">fesetround</span></span></a><span class="br0">(</span><a href="cpp-numeric-fenv-FE_round.html"><span class="kw1466">FE_TOWARDZERO</span></a><span class="br0">)</span><span class="sy4">;</span>
result <span class="sy1">=</span> <a href="cpp-numeric-math-rint.html"><span class="kw1354">std::<span class="me2">rint</span></span></a><span class="br0">(</span><a href="cpp-numeric-math-copysign.html"><span class="kw1364">std::<span class="me2">copysign</span></span></a><span class="br0">(</span><span class="nu16">0.5</span> <span class="sy2">+</span> <a href="cpp-numeric-math-fabs.html"><span class="kw1302">std::<span class="me2">fabs</span></span></a><span class="br0">(</span>x<span class="br0">)</span>, x<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-numeric-fenv-feround.html"><span class="kw1453">std::<span class="me2">fesetround</span></span></a><span class="br0">(</span>save_round<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-numeric-fenv-feupdateenv.html"><span class="kw1457">std::<span class="me2">feupdateenv</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>save_env<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> result<span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<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;cmath&gt;</span>
<span class="co2">#include &lt;cfenv&gt;</span>
<span class="co2">#include &lt;climits&gt;</span>
<span class="co2">#pragma STDC FENV_ACCESS ON</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="co1">// round</span>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;round(+2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="nu16">2.3</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; round(+2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="nu16">2.5</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; round(+2.7) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="nu16">2.7</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;round(-2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.3</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; round(-2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.5</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; round(-2.7) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.7</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>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;round(-0.0) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">0.0</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;round(-Inf) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">round</span><span class="br0">(</span><span class="sy2">-</span><a href="cpp-numeric-math-INFINITY.html"><span class="kw1374">INFINITY</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="co1">// lround</span>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lround(+2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="nu16">2.3</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; lround(+2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="nu16">2.5</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; lround(+2.7) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="nu16">2.7</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lround(-2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.3</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; lround(-2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.5</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot; lround(-2.7) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">2.7</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>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lround(-0.0) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">0.0</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lround(-Inf) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><span class="sy2">-</span><a href="cpp-numeric-math-INFINITY.html"><span class="kw1374">INFINITY</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="co1">// &#38169;&#35823;&#22788;&#29702;</span>
<a href="cpp-numeric-fenv-feclearexcept.html"><span class="kw1447">std::<span class="me2">feclearexcept</span></span></a><span class="br0">(</span><a href="cpp-numeric-fenv-FE_exceptions.html"><span class="kw1458">FE_ALL_EXCEPT</span></a><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;std::lround(LONG_MAX+1.5) = &quot;</span>
<span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lround</span><span class="br0">(</span><a href="cpp-types-climits.html"><span class="kw399">LONG_MAX</span></a><span class="sy2">+</span><span class="nu16">1.5</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="kw1">if</span> <span class="br0">(</span><a href="cpp-numeric-fenv-fetestexcept.html"><span class="kw1448">std::<span class="me2">fetestexcept</span></span></a><span class="br0">(</span><a href="cpp-numeric-fenv-FE_exceptions.html"><span class="kw1461">FE_INVALID</span></a><span class="br0">)</span><span class="br0">)</span>
<a href="cpp-io-cout.html"><span class="kw1755">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; FE_INVALID was raised<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">round(+2.3) = 2 round(+2.5) = 3 round(+2.7) = 3
round(-2.3) = -2 round(-2.5) = -3 round(-2.7) = -3
round(-0.0) = -0
round(-Inf) = -inf
lround(+2.3) = 2 lround(+2.5) = 3 lround(+2.7) = 3
lround(-2.3) = -2 lround(-2.5) = -3 lround(-2.7) = -3
lround(-0.0) = 0
lround(-Inf) = -9223372036854775808
std::lround(LONG_MAX+1.5) = -9223372036854775808
FE_INVALID was raised</pre></div>
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<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-numeric-math-floor.html"><span class="t-lines"><span>floor</span><span>floorf</span><span>floorl</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>&#19981;&#22823;&#20110;&#32473;&#23450;&#20540;&#30340;&#26368;&#25509;&#36817;&#25972;&#25968;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-numeric-math-ceil.html"><span class="t-lines"><span>ceil</span><span>ceilf</span><span>ceill</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>&#19981;&#23567;&#20110;&#32473;&#23450;&#20540;&#30340;&#26368;&#25509;&#36817;&#25972;&#25968;&#20540;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-numeric-math-trunc.html"><span class="t-lines"><span>trunc</span><span>truncf</span><span>truncl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>&#32477;&#23545;&#20540;&#19981;&#22823;&#20110;&#32473;&#23450;&#20540;&#30340;&#26368;&#25509;&#36817;&#25972;&#25968;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
</table>
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<div class="visualClear"></div>
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