# rint (3p) - Linux Man Pages

### rint: round-to-nearest integral value

## PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.## NAME

rint, rintf, rintl - round-to-nearest integral value

## SYNOPSIS

**#include <math.h>
**

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

*x*

**);**

long double rintl(long double

long double rintl(long double

*x*

**);**

## DESCRIPTION

These functions shall return the integral value (represented as a
**double**) nearest *x* in the direction of the
current rounding mode. The current rounding mode is implementation-defined.

If the current rounding mode rounds toward negative infinity, then
*rint*() shall be equivalent to *floor*(). If the current
rounding mode rounds toward positive infinity, then *rint*() shall
be
equivalent to *ceil*().

These functions differ from the *nearbyint*(), *nearbyintf*(),
and *nearbyintl*()
functions only in that they may raise the inexact floating-point exception
if the result differs in value from the argument.

An application wishing to check for error situations should set *errno*
to zero and call
*feclearexcept*(FE_ALL_EXCEPT) before calling these functions.
On return, if *errno* is non-zero or
*fetestexcept*(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.

## RETURN VALUE

Upon successful completion, these functions shall return the integer
(represented as a double precision number) nearest *x*
in the direction of the current rounding mode.

If
*x* is NaN, a NaN shall be returned.

If *x* is ±0 or ±Inf, *x* shall be returned.

If the correct value would cause overflow, a range error shall occur
and *rint*(), *rintf*(), and *rintl*() shall
return the value of the macro ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL
(with the same sign as *x*),
respectively.

## ERRORS

These functions shall fail if:

- Range Error
- The result would cause an overflow.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow floating-point exception shall be raised.

*The following sections are informative.*

## EXAMPLES

## APPLICATION USAGE

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

## RATIONALE

## FUTURE DIRECTIONS

## SEE ALSO

*abs*(), *ceil*(), *feclearexcept*(), *fetestexcept*(),
*floor*(), *isnan*(), *nearbyint*(), the
Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment
of Error Conditions for Mathematical Functions, *<math.h>*

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

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