klarkxy/hustoj
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
3256c00dcdf3190e1864c02ce50e1380b6b175cf
hustoj/web/cppreference-zh/chmhelp/cpp-numeric-math-rint.html
klarkxy 196e706fe4 上传cppreference
2025-08-01 12:57:54 +08:00

281 lines
28 KiB
HTML
Raw Blame History

<!DOCTYPE html>
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>std::rint, std::rintf, std::rintl, std::lrint, std::lrintf, std::lrintl, std::llrint, std::llrintf</title>
<link rel="stylesheet" href="ext.css" />
<link rel="stylesheet" href="site_modules.css" />
</head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_math_rint skin-cppreference2 action-view cpp-navbar">
<div id="cpp-content-base">
<div id="content"><a id="top"></a>
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>rint, <span style="font-size:0.7em; line-height:130%">std::</span>rintf, <span style="font-size:0.7em; line-height:130%">std::</span>rintl, <span style="font-size:0.7em; line-height:130%">std::</span>lrint, <span style="font-size:0.7em; line-height:130%">std::</span>lrintf, <span style="font-size:0.7em; line-height:130%">std::</span>lrintl, <span style="font-size:0.7em; line-height:130%">std::</span>llrint, <span style="font-size:0.7em; line-height:130%">std::</span>llrintf</h1>
<div id="bodyContent">
<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>
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
<table class="t-dcl-begin">
<tbody>
<tr class="t-dsc-header">
<td>
<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-cmath.html">&lt;cmath&gt;</a></code></div>
</td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span> &nbsp; &nbsp; &nbsp; rint <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; rintf<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>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span> &nbsp; &nbsp; &nbsp;rint <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span> rint <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> rintl<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>
</td>
<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span> &nbsp; &nbsp; &nbsp;rint <span class="br0">(</span> IntegralType arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(4)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lrint <span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span><br />
<span class="kw4">long</span> lrintf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(5)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lrint <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(6)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lrint <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> lrintl<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>
</td>
<td>(7)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> lrint <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>
</tr>
<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> llrint <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> llrintf<span class="br0">(</span> <span class="kw4">float</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(9)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<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> llrint <span class="br0">(</span> <span class="kw4">double</span> arg <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(10)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<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> llrint <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> llrintl<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>
</td>
<td>(11)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<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> llrint <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>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<div class="t-li1"><span class="t-li">1-3)</span> &#29992;<a href="cpp-numeric-fenv-FE_round.html">&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;</a>&#65292;&#33293;&#20837;&#28014;&#28857;&#21442;&#25968; <code>arg</code> &#20026;&#25972;&#25968;&#20540;&#65288;&#20197;&#28014;&#28857;&#26684;&#24335;&#65289;&#12290;</div>
<div class="t-li1"><span class="t-li">5-7, 9-11)</span> &#29992;<a href="cpp-numeric-fenv-FE_round.html">&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;</a>&#65292;&#33293;&#20837;&#28014;&#28857;&#21442;&#25968; <code>arg</code> &#20026;&#25972;&#25968;&#20540;&#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; <span class="t-v">(2,6,10)</span> &#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> &#25353;&#29031;<a href="cpp-numeric-fenv-FE_round.html">&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;</a>&#30340;&#26368;&#25509;&#36817;&#25972;&#25968;&#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::lrint</code> &#25110; <code>std::llrint</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::rint</code> &#20989;&#25968;&#65306;</dd>
</dl>
<ul>
<li>&#33509; <code>arg</code> &#20026; &plusmn;&infin; &#65292;&#21017;&#36820;&#22238;&#19981;&#20462;&#25913;&#30340;&#21442;&#25968;</li>
<li>&#33509; <code>arg</code> &#20026; &plusmn;0 &#65292;&#21017;&#36820;&#22238;&#19981;&#20462;&#25913;&#30340;&#21442;&#25968;</li>
<li>&#33509; <code>arg</code> &#20026; NaN &#65292;&#21017;&#36820;&#22238; NaN</li>
</ul>
<dl>
<dd>&#23545;&#20110; <code>std::lrint</code> &#21644; <code>std::llrint</code> &#20989;&#25968;&#65306;</dd>
</dl>
<ul>
<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;</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;</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;</li>
</ul>
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">&#27880;&#24847;</span></h3>
<p><a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/lrint.html">POSIX &#25351;&#23450;</a> <code>std::lrint</code> &#25110; <code>std::llrint</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>&#22914; <span class="t-lc"><a href="cpp-numeric-math-math_errhandling.html">math_errhandling</a></span> &#20013;&#25351;&#23450;&#65292; <code>std::rint</code> &#22312;&#33293;&#20837;&#38750;&#25972;&#25968;&#26377;&#38480;&#20540;&#26102;&#21487;&#20197;&#65288;&#20294;&#19981;&#22312;&#38750; IEEE &#28014;&#28857;&#24179;&#21488;&#19978;&#35201;&#27714;&#65289;&#24341;&#21457; <span class="t-lc"><a href="cpp-numeric-fenv-FE_exceptions.html">FE_INEXACT</a></span> &#12290;</p>
<p><code>std::rint</code> &#21644; <span class="t-lc"><a href="cpp-numeric-math-nearbyint.html">std::nearbyint</a></span> &#38388;&#20165;&#26377;&#30340;&#21306;&#21035;&#26159; <span class="t-lc"><a href="cpp-numeric-math-nearbyint.html">std::nearbyint</a></span> &#20915;&#19981;&#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;&#37117;&#26159;&#20934;&#30830;&#30340;&#25972;&#25968;&#65292;&#25925; <code>std::rint</code> &#33258;&#36523;&#20915;&#19981;&#19978;&#28322;&#65307;&#28982;&#32780;&#22312;&#23384;&#20648;&#32467;&#26524;&#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>&#33509;&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;&#20026;&hellip;&hellip;</p>
<ul>
<li><span class="t-lc"><a href="cpp-numeric-fenv-FE_round.html">FE_DOWNWARD</a></span> &#65292;&#21017; <code>std::rint</code> &#31561;&#20215;&#20110; <span class="t-lc"><a href="cpp-numeric-math-floor.html">std::floor</a></span> &#12290;</li>
<li><span class="t-lc"><a href="cpp-numeric-fenv-FE_round.html">FE_UPWARD</a></span> &#65292;&#21017; <code>std::rint</code> &#31561;&#20215;&#20110; <span class="t-lc"><a href="cpp-numeric-math-ceil.html">std::ceil</a></span> &#12290;</li>
<li><span class="t-lc"><a href="cpp-numeric-fenv-FE_round.html">FE_TOWARDZERO</a></span> &#65292;&#21017; <code>std::rint</code> &#31561;&#20215;&#20110; <span class="t-lc"><a href="cpp-numeric-math-trunc.html">std::trunc</a></span> &#12290;</li>
<li><span class="t-lc"><a href="cpp-numeric-fenv-FE_round.html">FE_TONEAREST</a></span> &#65292;&#21017; <code>std::rint</code> &#22312;&#20013;&#28857;&#24773;&#20917;&#21644; <span class="t-lc"><a href="cpp-numeric-math-round.html">std::round</a></span> &#30340;&#21306;&#21035;&#26159;&#21069;&#32773;&#22987;&#32456;&#33293;&#20837;&#21040;&#20598;&#25968;&#65292;&#32780;&#38750;&#36828;&#31163;&#38646;&#12290;</li>
</ul>
<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="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="co2">#pragma STDC FENV_ACCESS ON</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="kw1465">FE_TONEAREST</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;rounding to nearest (halfway cases to even):<span class="es1">\n</span>&quot;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;rint(+2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(+2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(+3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</span><span class="br0">(</span><span class="nu16">3.5</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;rint(-2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(-2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(-3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">3.5</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>
<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="kw1464">FE_DOWNWARD</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;rounding down:<span class="es1">\n</span>&quot;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;rint(+2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(+2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(+3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</span><span class="br0">(</span><span class="nu16">3.5</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;rint(-2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(-2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</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; rint(-3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">3.5</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;rounding down with lrint<span class="es1">\n</span>&quot;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lrint(+2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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; lrint(+2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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; lrint(+3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</span><span class="br0">(</span><span class="nu16">3.5</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;lrint(-2.3) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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; lrint(-2.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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; lrint(-3.5) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</span><span class="br0">(</span><span class="sy2">-</span><span class="nu16">3.5</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>
<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;lrint(-0.0) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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;lrint(-Inf) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</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::rint(0.1) = &quot;</span> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">rint</span><span class="br0">(</span><span class="nu18">.1</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="kw1460">FE_INEXACT</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_INEXACT was raised<span class="es1">\n</span>&quot;</span><span class="sy4">;</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::lrint(LONG_MIN-2048.0) = &quot;</span>
<span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">lrint</span><span class="br0">(</span>LONG_MIN<span class="sy2">-</span><span class="nu16">2048.0</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="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">rounding to nearest (halfway cases to even):
rint(+2.3) = 2 rint(+2.5) = 2 rint(+3.5) = 4
rint(-2.3) = -2 rint(-2.5) = -2 rint(-3.5) = -4
rounding down:
rint(+2.3) = 2 rint(+2.5) = 2 rint(+3.5) = 3
rint(-2.3) = -3 rint(-2.5) = -3 rint(-3.5) = -4
rounding down with lrint
lrint(+2.3) = 2 lrint(+2.5) = 2 lrint(+3.5) = 3
lrint(-2.3) = -3 lrint(-2.5) = -3 lrint(-3.5) = -4
lrint(-0.0) = 0
lrint(-Inf) = -9223372036854775808
std::rint(0.1) = 0
FE_INEXACT was raised
std::lrint(LONG_MIN-2048.0) = -9223372036854775808
FE_INVALID was raised</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-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>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-numeric-math-nearbyint.html"><span class="t-lines"><span>nearbyint</span><span>nearbyintf</span><span>nearbyintl</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>&#20351;&#29992;&#24403;&#21069;&#33293;&#20837;&#27169;&#24335;&#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-fenv-feround.html"><span class="t-lines"><span>fegetround</span><span>fesetround</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></div>
</div>
</td>
<td>&#33719;&#21462;&#25110;&#35774;&#32622;&#33293;&#20837;&#26041;&#21521;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
</table>
</div>
<div class="visualClear"></div>
</div>
</div>
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink