std::acos, std::acosf, std::acosl - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| (1) | ||
| float acos ( float num ); double acos ( double num ); long double acos ( long double num ); | (until C++23) | |
| /*floating-point-type*/ acos ( /*floating-point-type*/ num ); | (since C++23) (constexpr since C++26) | |
| float acosf( float num ); | (2) | (since C++11) (constexpr since C++26) |
| long double acosl( long double num ); | (3) | (since C++11) (constexpr since C++26) |
| SIMD overload (since C++26) | ||
| Defined in header | ||
| template< /*math-floating-point*/ V > constexpr /*deduced-simd-t*/<V> acos ( const V& v_num ); | (S) | (since C++26) |
| Additional overloads (since C++11) | ||
| Defined in header | ||
| template< class Integer > double acos ( Integer num ); | (A) | (constexpr since C++26) |
1-3) Computes the principal value of the arc cosine of num. The library provides overloads of std::acos 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) |
|---|
[edit] Parameters
| num | - | floating-point or integer value |
|---|
[edit] Return value
If no errors occur, the arc cosine of num (arccos(num)) in the range [0, π], is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported).
If a range error occurs due to underflow, the correct result (after rounding) is returned.
[edit] Error handling
Errors are reported as specified in math_errhandling.
Domain error occurs if num is outside the range [-1.0, 1.0].
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is +1, the value
+0is returned. - If |num| > 1, a domain error occurs and NaN is returned.
- if the argument is NaN, NaN is returned.
[edit] Notes
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::acos(num) has the same effect as std::acos(static_cast<double>(num)).
[edit] Example
#include #include #include #include #include // #pragma STDC FENV_ACCESS ON int main() { std::cout << "acos(-1) = " << std::acos(-1) << '\n' << "acos(0.0) = " << std::acos(0.0) << '\n' << "2acos(0.0) = " << 2 * std::acos(0) << '\n' << "acos(0.5) = " << std::acos(0.5) << '\n' << "3acos(0.5) = " << 3 * std::acos(0.5) << '\n' << "acos(1) = " << std::acos(1) << '\n'; // error handling errno = 0; std::feclearexcept(FE_ALL_EXCEPT); std::cout << "acos(1.1) = " << std::acos(1.1) << '\n'; if (errno == EDOM) std::cout << " errno == EDOM: " << std::strerror(errno) << '\n'; if (std::fetestexcept(FE_INVALID)) std::cout << " FE_INVALID raised" << '\n'; }
Output:
acos(-1) = 3.14159 acos(0.0) = 1.5708 2acos(0.0) = 3.14159 acos(0.5) = 1.0472 3acos(0.5) = 3.14159 acos(1) = 0 acos(1.1) = nan errno == EDOM: Numerical argument out of domain FE_INVALID raised
[edit] See also
| asinasinfasinl(C++11)(C++11) | computes arc sine (\({\small\arcsin{x}}\)arcsin(x)) (function) [edit] |
|---|---|
| atanatanfatanl(C++11)(C++11) | computes arc tangent (\({\small\arctan{x}}\)arctan(x)) (function) [edit] |
| atan2atan2fatan2l(C++11)(C++11) | arc tangent, using signs to determine quadrants (function) [edit] |
| coscosfcosl(C++11)(C++11) | computes cosine (\({\small\cos{x}}\)cos(x)) (function) [edit] |
| acos(std::complex)(C++11) | computes arc cosine of a complex number (\({\small\arccos{z}}\)arccos(z)) (function template) [edit] |
| acos(std::valarray) | applies the function std::acos to each element of valarray (function template) [edit] |
| C documentation for acos |