ceil, ceilf, ceill
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                    | 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.| Contents | 
[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 argis ±∞, it is returned, unmodified
-  If argis ±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
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
| (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) | 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 | |


