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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December 6, 2001 posix.fail