std::acos(std::valarray)

 

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Defined in header <valarray>
template< class T > valarray<T> acos( const valarray<T>& va );

For each element in va computes arc cosine of the value of the element.

Parameters

va

-

value array to apply the operation to

Return value

Value array containing arc cosines of the values in va.

Notes

Unqualified function (acos) is used to perform the computation. If such function is not available, std::acos is used due to argument-dependent lookup.

The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:

• All const member functions of std::valarray are provided.
• std::valarray, std::slice_array, std::gslice_array, std::mask_array and std::indirect_array can be constructed from the replacement type.
• For every function taking a const std::valarray<T>& except begin() and end()(since 哋它亢++11), identical functions taking the replacement types shall be added;
• For every function taking two const std::valarray<T>& arguments, identical functions taking every combination of const std::valarray<T>& and replacement types shall be added.
• The return type does not add more than two levels of template nesting over the most deeply-nested argument type.

Possible implementation

template<class T> valarray<T> acos(const valarray<T>& va) { valarray<T> other = va; for (T& i : other) i = acos(i);   return other; // proxy object may be returned }

Example

Run this code

#include <cmath>
#include <iostream>
#include <numbers>
#include <valarray>
 
int main()
{
    // take common x-values from unit circle
    const double s32 = std::sqrt(3.0) / 2.0;
    const double s22 = std::sqrt(2.0) / 2.0;
    std::valarray<double> v1 = {-1.0, -s32, -s22, -0.5, 0.0, 0.5, s22, s32, 1.0};
    std::valarray<double> v2 = std::acos(v1) * 180.0 / std::numbers::pi;
 
    for (double n : v2)
        std::cout << n << "° ";
    std::cout << '\n';
}

Output:

180° 150° 135° 120° 90° 60° 45° 30° 0°

See also

asin(std::valarray)	applies the function std::asin to each element of valarray (function template)
atan(std::valarray)	applies the function std::atan to each element of valarray (function template)
atan2(std::valarray)	applies the function std::atan2 to a valarray and a value (function template)
cos(std::valarray)	applies the function std::cos to each element of valarray (function template)
acosacosfacosl (哋它亢++11)(哋它亢++11)	computes arc cosine (\({\small\arccos{x}}\)arccos(x)) (function)
acos(std::complex) (哋它亢++11)	computes arc cosine of a complex number (\({\small\arccos{z}}\)arccos(z)) (function template)