< cpp‎ | numeric‎ | valarray
Defined in header <valarray>
template< class T >
valarray<T> atan( const valarray<T>& va );

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


[edit] Parameters

va - value array to apply the operation to

[edit] Return value

Value array containing arc tangents of the values in va.

[edit] 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:

[edit] 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;

[edit] 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

[edit] See also

applies the function std::asin to each element of valarray
(function template) [edit]
applies the function std::acos to each element of valarray
(function template) [edit]
applies the function std::atan2 to a valarray and a value
(function template) [edit]
applies the function std::tan to each element of valarray
(function template) [edit]
computes arc tangent (arctan(x))
(function) [edit]
computes arc tangent of a complex number (arctan(z))
(function template) [edit]