SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl − round to nearest integer

**#include
<math.h>**

**double
nearbyint(double** *x***);
float nearbyintf(float**

long double nearbyintl(long double

**double
rint(double** *x***);
float rintf(float**

long double rintl(long double

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*

The
**nearbyint**() functions round their argument to an
integer value in floating-point format, using the current
rounding direction (see **fesetround**(3)) and without
raising the *inexact* exception.

The
**rint**() functions do the same, but will raise the
*inexact* exception (**FE_INEXACT**, checkable via
**fetestexcept**(3)) when the result differs in value
from the argument.

These functions return the rounded integer value.

If *x* is
integral, +0, −0, NaN, or infinite, *x* itself is
returned.

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.

For an
explanation of the terms used in this section, see
**attributes**(7).

C99, POSIX.1-2001.

SUSv2 and
POSIX.1-2001 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
error-handling 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 IEEE-754 standard 32-bit and 64-bit floating-point
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.

**ceil**(3),
**floor**(3), **lrint**(3), **round**(3),
**trunc**(3)

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part of release 3.53 of the Linux *man-pages* project.
A description of the project, and information about
reporting bugs, can be found at
http://www.kernel.org/doc/man−pages/.