📄 cprojf.html
字号:
<!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>cproj</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="cproj"></a> <a name="tag_03_91"></a><!-- cproj --> <!--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_91_01"></a>NAME</h4><blockquote>cproj, cprojf, cprojl - complex projection functions</blockquote><h4><a name="tag_03_91_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/complex.h.html">complex.h</a>><br><br> double complex cproj(double complex</tt> <i>z</i><tt>);<br> float complex cprojf(float complex</tt> <i>z</i><tt>);<br> long double complex cprojl(long double complex</tt> <i>z</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_91_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 compute a projection of <i>z</i> onto the Riemann sphere: <i>z</i> projects to <i>z</i>, except that allcomplex infinities (even those with one infinite part and one NaN part) project to positive infinity on the real axis. If <i>z</i>has an infinite part, then <i>cproj</i>( <i>z</i>) shall be equivalent to:</p><pre><tt>INFINITY + I * copysign(0.0, cimag(z))</tt></pre></blockquote><h4><a name="tag_03_91_04"></a>RETURN VALUE</h4><blockquote><p>These functions shall return the value of the projection onto the Riemann sphere.</p></blockquote><h4><a name="tag_03_91_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_91_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_91_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_91_08"></a>RATIONALE</h4><blockquote><p>Two topologies are commonly used in complex mathematics: the complex plane with its continuum of infinities, and the Riemannsphere with its single infinity. The complex plane is better suited for transcendental functions, the Riemann sphere for algebraicfunctions. The complex types with their multiplicity of infinities provide a useful (though imperfect) model for the complex plane.The <i>cproj</i>() function helps model the Riemann sphere by mapping all infinities to one, and should be used just before anyoperation, especially comparisons, that might give spurious results for any of the other infinities. Note that a complex value withone infinite part and one NaN part is regarded as an infinity, not a NaN, because if one part is infinite, the complex value isinfinite independent of the value of the other part. For the same reason, <a href="../functions/cabs.html"><i>cabs</i>()</a>returns an infinity if its argument has an infinite part and a NaN part.</p></blockquote><h4><a name="tag_03_91_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_91_10"></a>SEE ALSO</h4><blockquote><p><a href="carg.html"><i>carg</i>()</a> , <a href="cimag.html"><i>cimag</i>()</a> , <a href="conj.html"><i>conj</i>()</a> , <ahref="creal.html"><i>creal</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/complex.h.html"><i><complex.h></i></a></p></blockquote><h4><a name="tag_03_91_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.</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
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -