ceil, ceilf, ceill - cppreference.com (original) (raw)

1-3) Computes the smallest integer value not less than arg.

1. 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.

Contents

• 1 Parameters
• 2 Return value
• 3 Error handling
• 4 Notes
• 5 Example
• 6 References
• 7 See also

[edit] Parameters

[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 <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; }

[edit] 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)); }

Possible output:

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

[edit] References

• C23 standard (ISO/IEC 9899:2024):

• 7.12.9.1 The ceil functions (p: TBD)

• 7.25 Type-generic math <tgmath.h> (p: TBD)

• F.10.6.1 The ceil functions (p: TBD)

• C17 standard (ISO/IEC 9899:2018):

• 7.12.9.1 The ceil functions (p: TBD)

• 7.25 Type-generic math <tgmath.h> (p: TBD)

• F.10.6.1 The ceil functions (p: TBD)

• 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