nearbyint, nearbyintf, nearbyintl

Parameters

Return value

The nearest integer value to arg , according to the current rounding mode , is returned.

Error handling

This function is not subject to any of the errors specified in math_errhandling .

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• FE_INEXACT is never raised.
• If arg is ±∞, it is returned, unmodified.
• If arg is ±0, it is returned, unmodified.
• If arg is NaN, NaN is returned.

Notes

The only difference between nearbyint and rint is that nearbyint never raises FE_INEXACT .

The largest representable floating-point values are exact integers in all standard floating-point formats, so nearbyint never overflows on its own; however the result may overflow any integer type (including intmax_t ), when stored in an integer variable.

If the current rounding mode is FE_TONEAREST , this function rounds to even in halfway cases (like rint , but unlike round ).

Example

#include <fenv.h>
#include <math.h>
#include <stdio.h>
 
int main(void)
{
// #pragma STDC FENV_ACCESS ON
    fesetround(FE_TONEAREST);
    printf("rounding to nearest:\nnearbyint(+2.3) = %+.1f  ", nearbyint(2.3));
    printf("nearbyint(+2.5) = %+.1f  ", nearbyint(2.5));
    printf("nearbyint(+3.5) = %+.1f\n", nearbyint(3.5));
    printf("nearbyint(-2.3) = %+.1f  ", nearbyint(-2.3));
    printf("nearbyint(-2.5) = %+.1f  ", nearbyint(-2.5));
    printf("nearbyint(-3.5) = %+.1f\n", nearbyint(-3.5));
 
    fesetround(FE_DOWNWARD);
    printf("rounding down: \nnearbyint(+2.3) = %+.1f  ", nearbyint(2.3));
    printf("nearbyint(+2.5) = %+.1f  ", nearbyint(2.5));
    printf("nearbyint(+3.5) = %+.1f\n", nearbyint(3.5));
    printf("nearbyint(-2.3) = %+.1f  ", nearbyint(-2.3));
    printf("nearbyint(-2.5) = %+.1f  ", nearbyint(-2.5));
    printf("nearbyint(-3.5) = %+.1f\n", nearbyint(-3.5));
 
    printf("nearbyint(-0.0) = %+.1f\n", nearbyint(-0.0));
    printf("nearbyint(-Inf) = %+.1f\n", nearbyint(-INFINITY));
}

rounding to nearest:
nearbyint(+2.3) = +2.0  nearbyint(+2.5) = +2.0  nearbyint(+3.5) = +4.0
nearbyint(-2.3) = -2.0  nearbyint(-2.5) = -2.0  nearbyint(-3.5) = -4.0
rounding down:
nearbyint(+2.3) = +2.0  nearbyint(+2.5) = +2.0  nearbyint(+3.5) = +3.0
nearbyint(-2.3) = -3.0  nearbyint(-2.5) = -3.0  nearbyint(-3.5) = -4.0
nearbyint(-0.0) = -0.0
nearbyint(-Inf) = -inf

References

See also