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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>rint</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="rint"></a> <a name="tag_03_612"></a><!-- rint --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_612_01"></a>NAME</h4><blockquote>rint, rintf, rintl - round-to-nearest integral value</blockquote><h4><a name="tag_03_612_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/math.h.html">math.h</a>><br><br> double rint(double</tt> <i>x</i><tt>);<br> float rintf(float</tt> <i>x</i><tt>);<br> long double rintl(long double</tt> <i>x</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_612_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>These functions shall return the integral value (represented as a <b>double</b>) nearest <i>x</i> in the direction of thecurrent rounding mode. The current rounding mode is implementation-defined.</p><p>If the current rounding mode rounds toward negative infinity, then <i>rint</i>() shall be equivalent to <a href="floor.html"><i>floor</i>()</a>. If the current rounding mode rounds toward positive infinity, then <i>rint</i>() shall beequivalent to <a href="ceil.html"><i>ceil</i>()</a>.</p><p>These functions differ from the <a href="../functions/nearbyint.html"><i>nearbyint</i>()</a>, <a href="../functions/nearbyintf.html"><i>nearbyintf</i>()</a>, and <a href="../functions/nearbyintl.html"><i>nearbyintl</i>()</a>functions only in that they may raise the inexact floating-point exception if the result differs in value from the argument.</p><p>An application wishing to check for error situations should set <i>errno</i> to zero and call<i>feclearexcept</i>(FE_ALL_EXCEPT) before calling these functions. On return, if <i>errno</i> is non-zero or<i>fetestexcept</i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.</p></blockquote><h4><a name="tag_03_612_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, these functions shall return the integer (represented as a double precision number) nearest <i>x</i>in the direction of the current rounding mode.</p><p><sup>[<a href="javascript:open_code('MX')">MX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> If<i>x</i> is NaN, a NaN shall be returned.</p><p>If <i>x</i> is ±0 or ±Inf, <i>x</i> shall be returned. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">If the correct value would cause overflow, a range error shall occur and <i>rint</i>(), <i>rintf</i>(), and <i>rintl</i>() shallreturn the value of the macro ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (with the same sign as <i>x</i>),respectively. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_612_05"></a>ERRORS</h4><blockquote><p>These functions shall fail if:</p><dl compact><dt>Range Error</dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The result would cause an overflow. <p>If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then <i>errno</i> shall be set to [ERANGE]. If theinteger expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.<img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_612_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_612_07"></a>APPLICATION USAGE</h4><blockquote><p>On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent ofeach other, but at least one of them must be non-zero.</p></blockquote><h4><a name="tag_03_612_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_612_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_612_10"></a>SEE ALSO</h4><blockquote><p><a href="abs.html"><i>abs</i>()</a>, <a href="ceil.html"><i>ceil</i>()</a>, <a href="feclearexcept.html"><i>feclearexcept</i>()</a>, <a href="fetestexcept.html"><i>fetestexcept</i>()</a>, <a href="floor.html"><i>floor</i>()</a>, <a href="isnan.html"><i>isnan</i>()</a>, <a href="nearbyint.html"><i>nearbyint</i>()</a>, theBase Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap04.html#tag_04_18">Section 4.18, Treatmentof Error Conditions for Mathematical Functions</a>, <a href="../basedefs/math.h.html"><i><math.h></i></a></p></blockquote><h4><a name="tag_03_612_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4, Version 2.</p></blockquote><h4><a name="tag_03_612_12"></a>Issue 5</h4><blockquote><p>Moved from X/OPEN UNIX extension to BASE.</p></blockquote><h4><a name="tag_03_612_13"></a>Issue 6</h4><blockquote><p>The following changes are made for alignment with the ISO/IEC 9899:1999 standard:</p><ul><li><p>The <i>rintf</i>() and <i>rintl</i>() functions are added.</p></li><li><p>The <i>rint</i>() function is no longer marked as an extension.</p></li><li><p>The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999standard.</p><p>IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.</p></li></ul></blockquote><div class="box"><em>End of informative text.</em></div><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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