std:: atan (std::valarray)

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

Parameters

Return value

Value array containing arc tangents of the values in va .

Notes

Unqualified function ( atan ) is used to perform the computation. If such function is not available, std:: atan 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 C++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> atan(const valarray<T>& va)
{
    valarray<T> other = va;
    for (T& i : other)
        i = atan(i);
 
    return other; // proxy object may be returned
}

Example

#include <algorithm>
#include <cmath>
#include <iostream>
#include <valarray>
 
auto show = [](char const* title, const std::valarray<float>& va)
{
    std::cout << title << " :";
    std::for_each(std::begin(va), std::end(va), 
        [](const float x) { std::cout << "  " << std::fixed << x; });
    std::cout << '\n';
};
 
int main()
{
    const std::valarray<float> x = {.1f, .3f, .6f, .9f};
    const std::valarray<float> f = std::atan(x);
    const std::valarray<float> g = std::tan(f);
 
    show("x          ", x);
    show("f = atan(x)", f);
    show("g = tan(f) ", g);
}

x           :  0.100000  0.300000  0.600000  0.900000
f = atan(x) :  0.099669  0.291457  0.540420  0.732815
g = tan(f)  :  0.100000  0.300000  0.600000  0.900000

See also