rint

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

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

LIBRARY

Math library (libm,~-lm)  

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():

    _POSIX_C_SOURCE >= 200112L || _ISOC99_SOURCE

rint():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || _XOPEN_SOURCE >= 500
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

rintf(), rintl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

 

DESCRIPTION

The nearbyint(), nearbyintf(), and nearbyintl() functions round their argument to an integer value in floatin-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 IEE-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.  

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.  

ATTRIBUTES

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

Interface	Attribute	Value
nearbyint(), nearbyintf(), nearbyintl(), rint(), rintf(), rintl()	Thread safety	M-Safe

 

STANDARDS

C11, POSIX.-2008.  

HISTORY

C99, POSIX.-2001. SUSv2 and POSIX.-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 erro-handling stuff was 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 IEE-754 standard 3-bit and 6-bit floatin-point numbers the maximum value of the exponent is 127 (respectively, 1023), and the number of mantissa bits including the implicit bit is 24 (respectively, 53).) This was removed in POSIX.-2008. 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)

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

STANDARDS

HISTORY

SEE ALSO