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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) 2001-2003 The Open Group, All Rights Reserved --><title>frexp</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="frexp"></a> <a name="tag_03_189"></a><!-- frexp --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_189_01"></a>NAME</h4><blockquote>frexp, frexpf, frexpl - extract mantissa and exponent from a double precision number</blockquote><h4><a name="tag_03_189_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/math.h.html">math.h</a>><br><br> double frexp(double</tt> <i>num</i><tt>, int *</tt><i>exp</i><tt>);<br> float frexpf(float</tt> <i>num</i><tt>, int *</tt><i>exp</i><tt>);<br> long double frexpl(long double</tt> <i>num</i><tt>, int *</tt><i>exp</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_189_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 break a floating-point number <i>num</i> into a normalized fraction and an integral power of 2. Theinteger exponent shall be stored in the <b>int</b> object pointed to by <i>exp</i>.</p></blockquote><h4><a name="tag_03_189_04"></a>RETURN VALUE</h4><blockquote><p>For finite arguments, these functions shall return the value <i>x</i>, such that <i>x</i> has a magnitude in the interval[½,1) or 0, and <i>num</i> equals <i>x</i> times 2 raised to the power *<i>exp</i>.</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>num</i> is NaN, a NaN shall be returned, and the value of *<i>exp</i> is unspecified.</p><p>If <i>num</i> is ±0, ±0 shall be returned, and the value of *<i>exp</i> shall be 0.</p><p>If <i>num</i> is ±Inf, <i>num</i> shall be returned, and the value of *<i>exp</i> is unspecified. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_189_05"></a>ERRORS</h4><blockquote><p>No errors are defined.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_189_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_189_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_189_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_189_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_189_10"></a>SEE ALSO</h4><blockquote><p><a href="isnan.html"><i>isnan</i>()</a> , <a href="ldexp.html"><i>ldexp</i>()</a> , <a href="modf.html"><i>modf</i>()</a> , theBase Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/math.h.html"><i><math.h></i></a></p></blockquote><h4><a name="tag_03_189_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_189_12"></a>Issue 5</h4><blockquote><p>The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in theAPPLICATION USAGE section.</p></blockquote><h4><a name="tag_03_189_13"></a>Issue 6</h4><blockquote><p>The <i>frexpf</i>() and <i>frexpl</i>() functions are added for alignment with the ISO/IEC 9899:1999 standard.<br></p><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></blockquote><div class="box"><em>End of informative text.</em></div><hr><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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