# std::atan(std::valarray)

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< 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.

### Parameters

va | - | value array to apply the operation to

### 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.
  - All functions accepting an argument of type const std::valarray & except `begin()` and `end()` (since C++11) should also accept the replacement type.
  - All functions accepting two arguments of type const std::valarray & should accept every combination of const std::valarray & and the replacement type.
  - 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;
    }

### Example

| This section is incomplete Reason: no example

### See also

asin(std::valarray) | applies the function std::asin to each element of valarray (function template)
acos(std::valarray) | applies the function std::acos to each element of valarray (function template)
atan2(std::valarray) | applies the function std::atan2 to a valarray and a value (function template)
tan(std::valarray) | applies the function std::tan to each element of valarray (function template)
atanatanfatanl (C++11)(C++11) | computes arc tangent (arctan(x)) (function)
atan(std::complex) (C++11) | computes arc tangent of a complex number (arctan(z)) (function template)

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