
RINT(3) Linux Programmer's Manual RINT(3)
NAME
nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl  round to nearest integer
SYNOPSIS
#include <math.h>
double nearbyint(double x);
float nearbyintf(float x);
long double nearbyintl(long double x);
double rint(double x);
float rintf(float x);
long double rintl(long double x);
Link with lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
nearbyint(), nearbyintf(), nearbyintl():
_XOPEN_SOURCE >= 600  _POSIX_C_SOURCE >= 200112L  _ISOC99_SOURCE;
or cc std=c99
rint():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 500 
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
rintf(), rintl():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
DESCRIPTION
The nearbyint(), nearbyintf(), and nearbyintl() functions round their argument to an inte
ger value in floatingpoint format, using the current rounding direction (see fes
etround(3)) and without raising the inexact exception.
The rint(), rintf(), and rintl() functions do the same, but will raise the inexact excep
tion (FE_INEXACT, checkable via fetestexcept(3)) when the result differs in value from the
argument.
RETURN VALUE
These functions return the rounded integer value.
If x is integral, +0, 0, NaN, or infinite, x itself is returned.
ERRORS
No errors occur. POSIX.12001 documents a range error for overflows, but see NOTES.
ATTRIBUTES
Multithreading (see pthreads(7))
The nearbyint(), nearbyintf(), nearbyintl(), rint(), rintf(), and rintl() functions are
threadsafe.
CONFORMING TO
C99, POSIX.12001.
NOTES
SUSv2 and POSIX.12001 contain text about overflow (which might set errno to ERANGE, or
raise an FE_OVERFLOW exception). In practice, the result cannot overflow on any current
machine, so this errorhandling stuff is just nonsense. (More precisely, overflow can
happen only when the maximum value of the exponent is smaller than the number of mantissa
bits. For the IEEE754 standard 32bit and 64bit floatingpoint numbers the maximum
value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24
(respectively, 53).)
If you want to store the rounded value in an integer type, you probably want to use one of
the functions described in lrint(3) instead.
SEE ALSO
ceil(3), floor(3), lrint(3), round(3), trunc(3)
COLOPHON
This page is part of release 3.55 of the Linux manpages project. A description of the
project, and information about reporting bugs, can be found at
http://www.kernel.org/doc/manpages/.
20130826 RINT(3) 
