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 IEEE Std 1003.1-2001 (“POSIX.1”) 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).

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.

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.

These functions shall fail if:

[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.

None.

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.

None.

None.

abs(3), ceil(3), feclearexcept(3), fetestexcept(3), floor(3), isnan(3), nearbyint(3), the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), xbd_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 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 (“ISO C99”) standard.

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

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January 1, 2004 posix.fail