2004-11-03 13:51:07 +00:00
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.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
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2008-08-01 05:26:40 +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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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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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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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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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 ROUND 3 2010-09-20 "" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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round, roundf, roundl \- round to nearest integer, away from zero
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.sp
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.BI "double round(double " x );
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.br
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.BI "float roundf(float " x );
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.br
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.BI "long double roundl(long double " x );
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.fi
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.sp
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2007-07-08 12:11:40 +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 round (),
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.BR roundf (),
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.BR roundl ():
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2010-09-18 15:51:14 +00:00
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.RS 4
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2010-09-18 15:52:50 +00:00
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
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_POSIX_C_SOURCE\ >=\ 200112L;
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2010-09-18 15:51:14 +00:00
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.br
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or
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2007-07-08 12:11:40 +00:00
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.I cc\ -std=c99
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2010-09-18 15:51:14 +00:00
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.RE
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.ad
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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These functions round \fIx\fP to the nearest integer, but
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round halfway cases away from zero (regardless of the current rounding
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2008-08-07 11:46:19 +00:00
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direction, see
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.BR fenv (3)),
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instead of to the nearest even integer like
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2007-05-12 00:30:29 +00:00
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.BR rint (3).
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2008-08-01 05:26:40 +00:00
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For example,
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.IR round(0.5)
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is 1.0, and
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.IR round(\-0.5)
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is \-1.0.
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2004-11-03 13:51:07 +00:00
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.SH "RETURN VALUE"
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2008-08-01 05:26:40 +00:00
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These functions return the rounded integer value.
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If \fIx\fP is integral, +0, \-0, NaN, or infinite,
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2004-11-03 13:51:07 +00:00
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\fIx\fP itself is returned.
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.SH ERRORS
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2008-08-01 05:26:40 +00:00
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No errors occur.
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2008-08-04 16:00:58 +00:00
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POSIX.1-2001 documents a range error for overflows, but see NOTES.
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2008-08-11 17:13:47 +00:00
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.SH VERSIONS
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These functions first appeared in glibc in version 2.1.
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2007-05-19 04:30:20 +00:00
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.SH "CONFORMING TO"
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2008-08-01 05:26:40 +00:00
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C99, POSIX.1-2001.
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2004-11-03 13:51:07 +00:00
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.SH NOTES
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2006-08-03 13:57:30 +00:00
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POSIX.1-2001 contains text about overflow (which might set
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2004-11-03 13:51:07 +00:00
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.I errno
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2007-06-22 19:42:52 +00:00
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to
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.BR ERANGE ,
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2008-08-01 05:26:40 +00:00
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or raise an
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.B FE_OVERFLOW
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exception).
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2004-11-03 13:51:07 +00:00
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In practice, the result cannot overflow on any current machine,
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so this error-handling stuff is just nonsense.
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2008-08-01 05:26:40 +00:00
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.\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point.
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2004-11-03 13:51:07 +00:00
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(More precisely, overflow can happen only when the maximum value
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of the exponent is smaller than the number of mantissa bits.
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2008-08-01 05:26:40 +00:00
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For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
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the maximum value of the exponent is 128 (respectively, 1024),
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and the number of mantissa bits is 24 (respectively, 53).)
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If you want to store the rounded value in an integer type,
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you probably want to use one of the functions described in
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.BR lround (3)
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instead.
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2004-11-03 13:51:07 +00:00
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.SH "SEE ALSO"
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.BR ceil (3),
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.BR floor (3),
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.BR lround (3),
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.BR nearbyint (3),
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.BR rint (3),
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.BR trunc (3)
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