std::ceil, std::ceilf, std::ceill
From cppreference.com
Defined in header <cmath>
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float ceil ( float arg ); |
(1) | (constexpr since C++23) |
float ceilf( float arg ); |
(2) | (since C++11) (constexpr since C++23) |
double ceil ( double arg ); |
(3) | (constexpr since C++23) |
long double ceil ( long double arg ); |
(4) | (constexpr since C++23) |
long double ceill( long double arg ); |
(5) | (since C++11) (constexpr since C++23) |
double ceil ( IntegralType arg ); |
(6) | (since C++11) (constexpr since C++23) |
1-5) Computes the smallest integer value not less than
arg
. 6) A set of overloads or a function template accepting an argument of any integral type. Equivalent to (3) (the argument is cast to double).
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
arg
is ±∞, it is returned unmodified - If
arg
is ±0, it is returned, unmodified - If arg is 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 std::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 the following code:
#include <cmath> #include <cfenv> #pragma STDC FENV_ACCESS ON double ceil(double x) { double result; int save_round = std::fegetround(); std::fesetround(FE_UPWARD); result = std::rint(x); // or std::nearbyint std::fesetround(save_round); return result; }
Example
Run this code
#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) |