std::atan2(std::valarray)

 

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valarray::valarray valarray::~valarray valarray::operator= valarray::operator[] valarray::swap valarray::size valarray::resize valarray::sum valarray::min valarray::max valarray::shift valarray::cshift valarray::apply	valarray::operator+valarray::operator-valarray::operator~valarray::operator! valarray::operator+=valarray::operator-=valarray::operator*=valarray::operator/=valarray::operator%=valarray::operator&=valarray::operator|=valarray::operator^=valarray::operator<<=valarray::operator>>=
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swap(std::valarray) (C++11) begin(std::valarray) (C++11)   end(std::valarray) (C++11) abs exp log log10 pow sqrt sin cos tan asin acos atan atan2 sinh cosh tanh	operator*operator/operator%operator+operator-operator^operator&operator|operator<<operator>>operator&&operator|| operator==operator!=operator<operator>operator<=operator>=
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Defined in header <valarray>
template<class T > std::valarray<T> atan2(conststd::valarray<T>& y, conststd::valarray<T>& x );	(1)
template<class T > std::valarray<T> atan2(conststd::valarray<T>& y,                         consttypenamestd::valarray<T>::value_type& vx );	(2)
template<class T > std::valarray<T> atan2(consttypenamestd::valarray<T>::value_type& vy,                         conststd::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.
• For every function taking a conststd::valarray<T>&except begin() and end()(since C++11), identical functions taking the replacement types shall be added;
• For every function taking two conststd::valarray<T>& arguments, identical functions taking every combination of conststd::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.

Example

Run this code

#include <algorithm>#include <cmath>#include <iomanip>#include <iostream>#include <valarray>   void show(charconst* title, conststd::valarray<double>& va){std::cout<< title <<' ';std::for_each(std::begin(va), std::end(va), [](constdouble x){std::cout<<' '<<std::right<<std::setw(4)<< x <<"°";});std::cout<<'\n';}   constdouble pi =std::acos(-1.0);// C++20: std::numbers::pi   int main(){auto degrees_to_radians =[](doubleconst& x){return(pi * x /180);};auto radians_to_degrees =[](doubleconst& x){return(180* x / pi);};   conststd::valarray<double> degrees{-90, -60, -45, -30, 0, 30, 45, 60, 90};conststd::valarray<double> radians = degrees.apply(degrees_to_radians);   constauto sin =std::sin(radians);constauto cos =std::cos(radians);   show("(1)", std::atan2(sin, cos).apply(radians_to_degrees)); show("(2)", std::atan2(sin/cos, 1.0).apply(radians_to_degrees)); show("(3)", std::atan2(1.0, cos/sin).apply(radians_to_degrees));}

Output:

(1) -90° -60° -45° -30° 0° 30° 45° 60° 90° (2) -90° -60° -45° -30° 0° 30° 45° 60° 90° (3) 90° 120° 135° 150° 0° 30° 45° 60° 90°

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

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)
atan(std::valarray)	applies the function std::atan to each element of valarray (function template)
atan2atan2fatan2l (C++11)(C++11)	arc tangent, using signs to determine quadrants (function)
arg	returns the phase angle (function template)