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

**#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**():

_POSIX_C_SOURCE >= 200112L ||
_ISOC99_SOURCE

**rint**():

_ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L

|| _XOPEN_SOURCE >= 500

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

**rintf**(),

**rintl**():

_ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

The

**nearbyint**(),

**nearbyintf**(), and

**nearbyintl**() 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. When the current rounding direction is to nearest,
these functions round halfway cases to the even integer in accordance with
IEEE-754.

The

**rint**(),

**rintf**(), and

**rintl**() 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).

Interface |
Attribute |
Value |

nearbyint (), nearbyintf (), nearbyintl (), rint (), rintf (), rintl
() |
Thread safety |
MT-Safe |

C99, POSIX.1-2001, POSIX.1-2008.

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)