ceil, ceilf, ceill

Parameters

Return value

If no errors occur, the smallest integer value not less than arg , that is ⌈arg⌉ , is returned.

Return value

Argument

Error handling

Errors are reported as specified in math_errhandling .

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

• The current rounding mode has no effect.
• If arg is ±∞, it is returned, unmodified.
• If arg is ±0, it is returned, unmodified.
• If arg is NaN, NaN is returned.

Notes

FE_INEXACT may be (but isn't required to be) raised when rounding a non-integer finite value.

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

This function (for double argument) behaves as if (except for the freedom to not raise FE_INEXACT ) implemented by

#include <fenv.h>
#include <math.h>
#pragma STDC FENV_ACCESS ON
 
double ceil(double x)
{
    double result;
    int save_round = fegetround();
    fesetround(FE_UPWARD);
    result = rint(x); // or nearbyint
    fesetround(save_round);
    return result;
}

Example

#include <math.h>
#include <stdio.h>
 
int main(void)
{
    printf("ceil(+2.4) = %+.1f\n", ceil(2.4));
    printf("ceil(-2.4) = %+.1f\n", ceil(-2.4));
    printf("ceil(-0.0) = %+.1f\n", ceil(-0.0));
    printf("ceil(-Inf) = %+f\n",   ceil(-INFINITY));
}

ceil(+2.4) = +3.0
ceil(-2.4) = -2.0
ceil(-0.0) = -0.0
ceil(-Inf) = -inf

References

See also