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# ceil, ceilf, ceill

From cppreference.com
< c‎ | numeric‎ | math

Defined in header `<math.h>` |  |
float ceilf( float arg ); | (1) | (since C99)
double ceil( double arg ); | (2) |
long double ceill( long double arg ); | (3) | (since C99)
Defined in header `<tgmath.h>` |  |
#define ceil( arg ) | (4) | (since C99)

1-3) Computes the smallest integer value not less than `arg`.
4) Type-generic macro: If `arg` has type long double, `ceill` is called. Otherwise, if `arg` has integer type or the type double, `ceil` is called. Otherwise, `ceilf` is called.

### [edit] Parameters

arg | - | floating point value

### [edit] Return value

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

Return value
Argument

### [edit] 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

### [edit] 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 <math.h>
    #include <fenv.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;
    }

### [edit] Example

Run this code

    #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));
    }

Possible output:

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

### [edit] References

- C11 standard (ISO/IEC 9899:2011):

  - 7.12.9.1 The ceil functions (p: 251)

  - 7.25 Type-generic math <tgmath.h> (p: 373-375)

  - F.10.6.1 The ceil functions (p: 526)

- C99 standard (ISO/IEC 9899:1999):

  - 7.12.9.1 The ceil functions (p: 231-232)

  - 7.22 Type-generic math <tgmath.h> (p: 335-337)

  - F.9.6.1 The ceil functions (p: 462-463)

- C89/C90 standard (ISO/IEC 9899:1990):

  - 4.5.6.1 The ceil function

### [edit] See also

floor floorf floorl (C99)(C99) | computes largest integer not greater than the given value (function) [edit]
trunc truncf truncl (C99)(C99)(C99) | rounds to nearest integer not greater in magnitude than the given value (function) [edit]
round lround llround (C99)(C99)(C99) | rounds to nearest integer, rounding away from zero in halfway cases (function) [edit]
nearbyint nearbyintf nearbyintl (C99)(C99)(C99) | rounds to an integer using current rounding mode (function) [edit]
rint rintf rintl lrint lrintf lrintl llrint llrintf llrintl (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) | rounds to an integer using current rounding mode with exception if the result differs (function) [edit]
C++ documentation for ceil

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