RINT(3) Library Functions Manual RINT(3)

rint rintf rintl — round-to-nearest integral value

#include <math.h>

double rint(double x);
float rintf(float x);
long double rintl(long double x);

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.1-2017 defers to the ISO C standard.

These functions shall return the integral value (represented as a ) 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(3). If the current rounding mode rounds toward positive infinity, then rint () shall be equivalent to ceil(3). If the current rounding mode rounds towards zero, then rint () shall be equivalent to trunc(3). [MX] If the current rounding mode rounds towards nearest, then rint () differs from round(3) in that halfway cases are rounded to even rather than away from zero.

These functions differ from the nearbyint(3), nearbyintf(3), and nearbyintl(3) 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 (FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

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] The result shall have the same sign as x.

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

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

No errors are defined.

None.

The integral value returned by these functions need not be expressible as an . The return value should be tested before assigning it to an integer type to avoid the undefined results of an integer overflow.

None.

None.

abs(3), ceil(3), feclearexcept(3), fetestexcept(3), floor(3), isnan(3), nearbyint(3)

XBD V1_chap04(7), <math.h>

First released in Issue 4, Version 2.

Moved from X/OPEN UNIX extension to BASE.

The following changes are made for alignment with the ISO/IEC 9899:1999 (“ISO C99”) standard:

  • The () and () 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 (“ISO C99”) standard.

    IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 (“ISO C99”) standard are marked.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0514 [346], XSH/TC1-2008/0515 [346], XSH/TC1-2008/0516 [346], XSH/TC1-2008/0517 [346], and XSH/TC1-2008/0518 [346] are applied.

January 31, 2018 posix.fail