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

1-3) Computes the least integer value not less than num. The library provides overloads of std::ceil for all cv-unqualified floating-point types as the type of the parameter.(since C++23)

Contents

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

[edit] Parameters

[edit] Return value

If no errors occur, the smallest integer value not less than num, that is ⌈num⌉, is returned.

Return value

num

[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 num is ±∞, it is returned unmodified.
• If num is ±0, it is returned, unmodified.
• If num is NaN, NaN is returned.

[edit] 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:

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)).

[edit] Example

#include #include   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

[edit] See also

[edit] External links