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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>erf</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_003_247"> </a>NAME</h4><blockquote>erf, erfc - error and complementary error functions</blockquote><h4><a name = "tag_000_003_248"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="math.h.html">math.h</a>>double erf(double <i>x</i>);double erfc(double <i>x</i>);</code></pre></blockquote><h4><a name = "tag_000_003_249"> </a>DESCRIPTION</h4><blockquote>The<i>erf()</i>function computes the error function of<i>x</i>,defined as:<br><img src="../images/erf.gif" border=0><p>The<i>erfc()</i>function computes 1.0 -<i>erf (x)</i><p>An application wishing to check for error situations should set<i>errno</i>to 0 before calling<i>erf()</i>.If<i>errno</i>is non-zero on return,or the return value is NaN,an error has occurred.</blockquote><h4><a name = "tag_000_003_250"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,<i>erf()</i>and<i>erfc()</i>return the value of the error function andcomplementary error function, respectively.<p>If<i>x</i>is NaN, NaN is returned and<i>errno</i>may be set to [EDOM].<p>If the correct value would cause underflow, 0 is returned and<i>errno</i>may be set to [ERANGE].</blockquote><h4><a name = "tag_000_003_251"> </a>ERRORS</h4><blockquote>The<i>erf()</i>and<i>erfc()</i>functions may fail if:<dl compact><dt>[EDOM]<dd>The value of<i>x</i>is NaN.<dt>[ERANGE]<dd>The result underflows.</dl><p>No other errors will occur.</blockquote><h4><a name = "tag_000_003_252"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_003_253"> </a>APPLICATION USAGE</h4><blockquote>The<i>erfc()</i>function is provided because of the extreme loss of relative accuracy if<i>erf ( x )</i>is called for large<i>x</i>and the result subtracted from 1.0.</blockquote><h4><a name = "tag_000_003_254"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_003_255"> </a>SEE ALSO</h4><blockquote><i><a href="isnan.html">isnan()</a></i>,<i><a href="math.h.html"><math.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from Issue 1 of the SVID.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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