std:: ceil, std:: ceilf, std:: ceill
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Defined in header
<cmath>
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||
| (1) | ||
|
float
ceil
(
float
num
)
;
double
ceil
(
double
num
)
;
|
(until C++23) | |
|
constexpr
/* floating-point-type */
ceil ( /* floating-point-type */ num ) ; |
(since C++23) | |
|
float
ceilf
(
float
num
)
;
|
(2) |
(since C++11)
(constexpr since C++23) |
|
long
double
ceill
(
long
double
num
)
;
|
(3) |
(since C++11)
(constexpr since C++23) |
|
Additional overloads
(since C++11)
|
||
|
Defined in header
<cmath>
|
||
|
template
<
class
Integer
>
double ceil ( Integer num ) ; |
(A) | (constexpr since C++23) |
std::ceil
for all cv-unqualified floating-point types as the type of the parameter.
(since C++23)
|
A)
Additional overloads are provided for all integer types, which are treated as
double
.
|
(since C++11) |
Parameters
| num | - | floating point or integer value |
Return value
If no errors occur, the smallest integer value not less than num , that is ⌈num⌉ , is returned.
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 num is ±∞, it is returned unmodified.
- If num is ±0, it is returned, unmodified.
- If num is NaN, NaN is returned.
Notes
FE_INEXACT may be (but is not 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 std::intmax_t ), when stored in an integer variable. It is for this reason that the return type is floating-point not integral.
This function (for double argument) behaves as if (except for the freedom to not raise FE_INEXACT ) implemented by the following code:
#include <cfenv> #include <cmath> #pragma STDC FENV_ACCESS ON double ceil(double x) { int save_round = std::fegetround(); std::fesetround(FE_UPWARD); double result = std::rint(x); // or std::nearbyint std::fesetround(save_round); return result; }
The additional overloads are not required to be provided exactly as (A) . They only need to be sufficient to ensure that for their argument num of integer type, std :: ceil ( num ) has the same effect as std :: ceil ( static_cast < double > ( num ) ) .
Example
#include <cmath> #include <iostream> int main() { std::cout << std::fixed << "ceil(+2.4) = " << std::ceil(+2.4) << '\n' << "ceil(-2.4) = " << std::ceil(-2.4) << '\n' << "ceil(-0.0) = " << std::ceil(-0.0) << '\n' << "ceil(-Inf) = " << std::ceil(-INFINITY) << '\n'; }
Output:
ceil(+2.4) = 3.000000 ceil(-2.4) = -2.000000 ceil(-0.0) = -0.000000 ceil(-Inf) = -inf
See also
|
(C++11)
(C++11)
|
nearest integer not greater than the given value
(function) |
|
(C++11)
(C++11)
(C++11)
|
nearest integer not greater in magnitude than the given value
(function) |
|
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
|
nearest integer, rounding away from zero in halfway cases
(function) |
|
(C++11)
(C++11)
(C++11)
|
nearest integer using current rounding mode
(function) |
|
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
|
nearest integer using current rounding mode with
exception if the result differs (function) |
|
C documentation
for
ceil
|
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External links
| Fast ceiling of an integer division — StackOverflow |