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std::atan2(std::valarray)

Defined in header <valarray>

Defined in header `<valarray>`
template< class T > std::valarray<T> atan2( const std::valarray<T>& y, const std::valarray<T>& x );	(1)
template< class T > std::valarray<T> atan2( const std::valarray<T>& y, const typename std::valarray<T>::value_type& vx );	(2)
template< class T > std::valarray<T> atan2( const typename std::valarray<T>::value_type& vy, const std::valarray<T>& x );	(3)

template< class T > 
std::valarray<T> atan2( const std::valarray<T>& y, const std::valarray<T>& x );

(1)

template< class T > 
std::valarray<T> atan2( const std::valarray<T>& y,
                        const typename std::valarray<T>::value_type& vx );

(2)

template< class T > 
std::valarray<T> atan2( const typename std::valarray<T>::value_type& vy,
                        const std::valarray<T>& x );

(3)

Computes the inverse tangent of y/x using the signs of arguments to correctly determine quadrant.

1) Computes the inverse tangent of each pair of corresponding values from y and x.

The behavior is undefined if x.size() != y.size().

2) Computes the inverse tangent of vx and each value in the numeric array y.

3) Computes the inverse tangent of vy and each value in the numeric array x.

Parameters

x, y	-	numeric arrays to compute inverse tangent of
vy, vx	-	values to compute inverse tangent of

Return value

A numeric array containing the results of computation of inverse tangent.

Notes

Unqualified function (atan2) is used to perform the computation. If such function is not available, std::atan2 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.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3074	C++98	`T` is deduced from both the scalar and the `valarray` for (2-3), disallowing mixed-type calls	only deduce `T` from the `valarray`

Example

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)
atan(std::valarray)	applies the function `std::atan` to each element of valarray (function template)
atan2	arc tangent, using signs to determine quadrants (function)
arg	returns the phase angle (function template)