2004-11-03 13:51:07 +00:00
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.\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>.
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2008-08-01 05:26:23 +00:00
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.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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2004-11-03 13:51:07 +00:00
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\" Permission is granted to copy and distribute modified versions of this
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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2004-11-03 13:51:07 +00:00
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2007-04-12 22:42:49 +00:00
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.\" Inspired by a page by Walter Harms created 2002-08-10
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_exit.2, brk.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, getdtablesize.2, gethostname.2, getpagesize.2, getsid.2, killpg.2, mknod.2, mknodat.2, poll.2, posix_fadvise.2, pread.2, readlink.2, setpgid.2, setreuid.2, sigaltstack.2, stat.2, symlink.2, sync.2, truncate.2, vfork.2, wait.2, wait4.2, a64l.3, abs.3, acos.3, acosh.3, asin.3, asinh.3, atan.3, atan2.3, atoi.3, cbrt.3, ceil.3, copysign.3, cosh.3, dirfd.3, div.3, ecvt.3, erf.3, erfc.3, exp.3, exp2.3, fabs.3, fdim.3, ffs.3, floor.3, fma.3, fmax.3, fmin.3, fmod.3, fpclassify.3, frexp.3, ftw.3, fwide.3, gcvt.3, getcwd.3, getdate.3, getgrent.3, gethostid.3, getpass.3, getpwent.3, getsubopt.3, getw.3, hypot.3, ilogb.3, index.3, isalpha.3, isgreater.3, iswblank.3, j0.3, ldexp.3, lockf.3, log.3, log10.3, log1p.3, logb.3, lrint.3, lround.3, mkstemp.3, mktemp.3, modf.3, mq_receive.3, mq_send.3, nan.3, nextafter.3, posix_fallocate.3, posix_memalign.3, printf.3, qecvt.3, random.3, realpath.3, remainder.3, remquo.3, rint.3, round.3, scalb.3, scalbln.3, scanf.3, siginterrupt.3, signbit.3, sigset.3, sinh.3, sqrt.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strfry.3, strpbrk.3, strsep.3, strspn.3, strstr.3, strtod.3, strtok.3, strtol.3, strtoul.3, strxfrm.3, tanh.3, tgamma.3, trunc.3, ttyslot.3, ualarm.3, usleep.3, wprintf.3, armscii-8.7, cp1251.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-3.7, iso_8859-5.7, iso_8859-6.7, iso_8859-8.7, koi8-u.7: tstamp
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-09-19 17:19:13 +00:00
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.TH ILOGB 3 2010-09-20 "" "Linux Programmer's Manual"
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.SH NAME
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ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value
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.SH SYNOPSIS
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.B #include <math.h>
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.sp
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.BI "int ilogb(double " x );
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.br
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.BI "int ilogbf(float " x );
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.br
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.BI "int ilogbl(long double " x );
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.sp
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2007-07-21 05:25:03 +00:00
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR ilogb ():
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2010-09-18 15:22:34 +00:00
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.RS 4
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2010-09-22 16:09:17 +00:00
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
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2010-09-18 15:27:55 +00:00
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED ||
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_ISOC99_SOURCE ||
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_POSIX_C_SOURCE\ >=\ 200112L;
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.br
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or
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.I cc\ -std=c99
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.RE
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.br
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.BR ilogbf (),
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.BR ilogbl ():
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2010-09-18 15:22:34 +00:00
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.RS 4
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2010-09-18 15:27:55 +00:00
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
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_POSIX_C_SOURCE\ >=\ 200112L;
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2010-09-18 15:22:34 +00:00
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.br
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or
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.I cc\ -std=c99
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2010-09-18 15:22:34 +00:00
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.RE
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.ad b
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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These functions return the exponent part of their argument
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2007-04-12 22:42:49 +00:00
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as a signed integer.
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When no error occurs, these functions
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are equivalent to the corresponding
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.BR logb (3)
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functions, cast to
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.IR int .
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.SH RETURN VALUE
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On success, these functions return the exponent of
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.IR x ,
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as a signed integer.
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2004-11-03 13:51:07 +00:00
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If
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.I x
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is zero, then a domain error occurs, and the functions return
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.\" the POSIX.1 spec for logb() says logb() gives pole error for this
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.\" case, but for ilogb() it says domain error.
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.BR FP_ILOGB0 .
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.\" glibc: The numeric value is either `INT_MIN' or `-INT_MAX'.
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If
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.I x
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is a NaN, then a domain error occurs, and the functions return
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.BR FP_ILOGBNAN .
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.\" glibc: The numeric value is either `INT_MIN' or `INT_MAX'.
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.\" On i386, FP_ILOGB0 and FP_ILOGBNAN have the same value.
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2004-11-03 13:51:07 +00:00
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If
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.I x
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is negative infinity or positive infinity, then
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a domain error occurs, and the functions return
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.BR INT_MAX .
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.\"
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.\" POSIX.1-2001 also says:
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.\" If the correct value is greater than {INT_MAX}, {INT_MAX}
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.\" shall be returned and a domain error shall occur.
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.\"
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.\" If the correct value is less than {INT_MIN}, {INT_MIN}
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.\" shall be returned and a domain error shall occur.
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.SH ERRORS
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See
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.BR math_error (7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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.PP
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The following errors can occur:
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.TP
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Domain error: \fIx\fP is 0 or a NaN
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.\" .I errno
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.\" is set to
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.\" .BR EDOM .
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An invalid floating-point exception
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.RB ( FE_INVALID )
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is raised.
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.IP
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These functions do not set
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.IR errno
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for this case.
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794
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.TP
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Domain error: \fIx\fP is an infinity
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.\" .I errno
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.\" is set to
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.\" .BR EDOM .
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.\" An invalid floating-point exception
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.\" .RB ( FE_INVALID )
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.\" is raised.
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.IP
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These functions do not set
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.IR errno
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or raise an exception for this case.
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.\" FIXME . Is it intentional that these functions do not set errno,
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.\" or raise an exception?
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.\" log(), log2(), log10() do set errno
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794
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2004-11-03 13:51:07 +00:00
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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.SH "SEE ALSO"
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.BR log (3),
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2009-02-03 03:59:38 +00:00
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.BR logb (3),
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.BR significand (3)
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