248 lines
5.1 KiB
HTML
248 lines
5.1 KiB
HTML
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<HTML><HEAD><TITLE>Man page of ILOGB</TITLE>
|
|
</HEAD><BODY>
|
|
<H1>ILOGB</H1>
|
|
Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
|
|
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
|
|
|
|
<A NAME="lbAB"> </A>
|
|
<H2>NAME</H2>
|
|
|
|
ilogb, ilogbf, ilogbl - get integer exponent of a floating-point value
|
|
<A NAME="lbAC"> </A>
|
|
<H2>SYNOPSIS</H2>
|
|
|
|
<B>#include <<A HREF="file:///usr/include/math.h">math.h</A>></B>
|
|
|
|
<P>
|
|
|
|
<B>int ilogb(double </B><I>x</I><B>);</B>
|
|
|
|
<BR>
|
|
|
|
<B>int ilogbf(float </B><I>x</I><B>);</B>
|
|
|
|
<BR>
|
|
|
|
<B>int ilogbl(long double </B><I>x</I><B>);</B>
|
|
|
|
<P>
|
|
|
|
Link with <I>-lm</I>.
|
|
<P>
|
|
|
|
|
|
Feature Test Macro Requirements for glibc (see
|
|
<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
|
|
|
|
|
|
<P>
|
|
|
|
|
|
<B>ilogb</B>():
|
|
|
|
<DL COMPACT><DT id="1"><DD>
|
|
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|
|
<BR> || _XOPEN_SOURCE >= 500
|
|
|
|
<BR> || /* Since glibc 2.19: */ _DEFAULT_SOURCE
|
|
<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
|
|
</DL>
|
|
|
|
<BR>
|
|
|
|
<B>ilogbf</B>(),
|
|
|
|
<B>ilogbl</B>():
|
|
|
|
<DL COMPACT><DT id="2"><DD>
|
|
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|
|
<BR> || /* Since glibc 2.19: */ _DEFAULT_SOURCE
|
|
<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
|
|
</DL>
|
|
|
|
|
|
<A NAME="lbAD"> </A>
|
|
<H2>DESCRIPTION</H2>
|
|
|
|
These functions return the exponent part of their argument
|
|
as a signed integer.
|
|
When no error occurs, these functions
|
|
are equivalent to the corresponding
|
|
<B><A HREF="/cgi-bin/man/man2html?3+logb">logb</A></B>(3)
|
|
|
|
functions, cast to
|
|
<I>int</I>.
|
|
|
|
<A NAME="lbAE"> </A>
|
|
<H2>RETURN VALUE</H2>
|
|
|
|
On success, these functions return the exponent of
|
|
<I>x</I>,
|
|
|
|
as a signed integer.
|
|
<P>
|
|
|
|
If
|
|
<I>x</I>
|
|
|
|
is zero, then a domain error occurs, and the functions return
|
|
|
|
|
|
<B>FP_ILOGB0</B>.
|
|
|
|
|
|
<P>
|
|
|
|
If
|
|
<I>x</I>
|
|
|
|
is a NaN, then a domain error occurs, and the functions return
|
|
<B>FP_ILOGBNAN</B>.
|
|
|
|
|
|
|
|
<P>
|
|
|
|
If
|
|
<I>x</I>
|
|
|
|
is negative infinity or positive infinity, then
|
|
a domain error occurs, and the functions return
|
|
<B>INT_MAX</B>.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<A NAME="lbAF"> </A>
|
|
<H2>ERRORS</H2>
|
|
|
|
See
|
|
<B><A HREF="/cgi-bin/man/man2html?7+math_error">math_error</A></B>(7)
|
|
|
|
for information on how to determine whether an error has occurred
|
|
when calling these functions.
|
|
<P>
|
|
|
|
The following errors can occur:
|
|
<DL COMPACT>
|
|
<DT id="3">Domain error: <I>x</I> is 0 or a NaN<DD>
|
|
An invalid floating-point exception
|
|
(<B>FE_INVALID</B>)
|
|
|
|
is raised, and
|
|
<I>errno</I>
|
|
|
|
is set to
|
|
<B>EDOM</B>
|
|
|
|
(but see BUGS).
|
|
<DT id="4"><DD>
|
|
<DT id="5">Domain error: <I>x</I> is an infinity<DD>
|
|
An invalid floating-point exception
|
|
(<B>FE_INVALID</B>)
|
|
|
|
is raised, and
|
|
<I>errno</I>
|
|
|
|
is set to
|
|
<B>EDOM</B>
|
|
|
|
(but see BUGS).
|
|
</DL>
|
|
<A NAME="lbAG"> </A>
|
|
<H2>ATTRIBUTES</H2>
|
|
|
|
For an explanation of the terms used in this section, see
|
|
<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
|
|
|
|
<TABLE BORDER>
|
|
<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
|
|
<TR VALIGN=top><TD>
|
|
<B>ilogb</B>(),
|
|
|
|
<B>ilogbf</B>(),
|
|
|
|
<B>ilogbl</B>()
|
|
|
|
</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
|
|
</TABLE>
|
|
|
|
<A NAME="lbAH"> </A>
|
|
<H2>CONFORMING TO</H2>
|
|
|
|
C99, POSIX.1-2001, POSIX.1-2008.
|
|
<A NAME="lbAI"> </A>
|
|
<H2>BUGS</H2>
|
|
|
|
|
|
Before version 2.16, the following bugs existed in the
|
|
glibc implementation of these functions:
|
|
<DL COMPACT>
|
|
<DT id="6">*<DD>
|
|
The domain error case where
|
|
<I>x</I>
|
|
|
|
is 0 or a NaN did not cause
|
|
<I>errno</I>
|
|
|
|
to be set or (on some architectures) raise a floating-point exception.
|
|
<DT id="7">*<DD>
|
|
The domain error case where
|
|
<I>x</I>
|
|
|
|
is an infinity did not cause
|
|
<I>errno</I>
|
|
|
|
to be set or raise a floating-point exception.
|
|
</DL>
|
|
<A NAME="lbAJ"> </A>
|
|
<H2>SEE ALSO</H2>
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?3+log">log</A></B>(3),
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?3+logb">logb</A></B>(3),
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?3+significand">significand</A></B>(3)
|
|
|
|
<A NAME="lbAK"> </A>
|
|
<H2>COLOPHON</H2>
|
|
|
|
This page is part of release 5.05 of the Linux
|
|
<I>man-pages</I>
|
|
|
|
project.
|
|
A description of the project,
|
|
information about reporting bugs,
|
|
and the latest version of this page,
|
|
can be found at
|
|
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
|
|
<P>
|
|
|
|
<HR>
|
|
<A NAME="index"> </A><H2>Index</H2>
|
|
<DL>
|
|
<DT id="8"><A HREF="#lbAB">NAME</A><DD>
|
|
<DT id="9"><A HREF="#lbAC">SYNOPSIS</A><DD>
|
|
<DT id="10"><A HREF="#lbAD">DESCRIPTION</A><DD>
|
|
<DT id="11"><A HREF="#lbAE">RETURN VALUE</A><DD>
|
|
<DT id="12"><A HREF="#lbAF">ERRORS</A><DD>
|
|
<DT id="13"><A HREF="#lbAG">ATTRIBUTES</A><DD>
|
|
<DT id="14"><A HREF="#lbAH">CONFORMING TO</A><DD>
|
|
<DT id="15"><A HREF="#lbAI">BUGS</A><DD>
|
|
<DT id="16"><A HREF="#lbAJ">SEE ALSO</A><DD>
|
|
<DT id="17"><A HREF="#lbAK">COLOPHON</A><DD>
|
|
</DL>
|
|
<HR>
|
|
This document was created by
|
|
<A HREF="/cgi-bin/man/man2html">man2html</A>,
|
|
using the manual pages.<BR>
|
|
Time: 00:05:46 GMT, March 31, 2021
|
|
</BODY>
|
|
</HTML>
|