SIMPLE SOLUTIONS

# RINT(3) - man page online | library functions

Round to nearest integer.

Chapter
2015-04-19
```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);

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 floating-point format, using the current rounding direction (see fes‐
etround(3)) and without raising the inexact exception.  When the current rounding direc‐
tion 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 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.1-2001 documents a range error for overflows, but see NOTES.

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

┌───────────────────────────┬───────────────┬─────────┐
│Interface                  │ Attribute     │ Value   │
├───────────────────────────┼───────────────┼─────────┤
│nearbyint(), nearbyintf(), │ Thread safety │ MT-Safe │
│nearbyintl(), rint(),      │               │         │
│rintf(), rintl()           │               │         │
└───────────────────────────┴───────────────┴─────────┘
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.

NOTES
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.