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 x);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

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.

^[MX] If x is NaN, a NaN shall be returned.

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

^[XSI] 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

^[XSI] 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.

EXAMPLES

None.

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

None.

FUTURE DIRECTIONS

None.

SEE ALSO

abs , ceil , feclearexcept , fetestexcept , floor , isnan , nearbyint

XBD Treatment of Error Conditions for Mathematical Functions , <math.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Issue 6

The following changes are made for alignment with the ISO/IEC 9899:1999 standard:

• The rintf() and rintl() functions are added.

• The rint() function is no longer marked as an extension.

• The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.

  IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.