ceil, ceilf, ceill
From cppreference.com
| Defined in header <math.h>
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float ceilf( float arg );
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(1) | (since C99) |
double ceil( double arg );
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(2) | |
long double ceill( long double arg );
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(3) | (since C99) |
| Defined in header <tgmath.h>
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#define ceil( arg )
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(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.Parameters
| arg | - | floating-point value |
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
argis ±∞, it is returned, unmodified. - If
argis ±0, it is returned, unmodified. - If
argis 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
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
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
See also
(C99)(C99) |
computes largest integer not greater than the given value (function) |
(C99)(C99)(C99) |
rounds to nearest integer not greater in magnitude than the given value (function) |
(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) |
rounds to nearest integer, rounding away from zero in halfway cases (function) |
(C99)(C99)(C99) |
rounds to an integer using current rounding mode (function) |
(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) |
rounds to an integer using current rounding mode with exception if the result differs (function) |
C++ documentation for ceil
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