std::atan2(std::valarray)
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Defined in header
<valarray>
template< class T >
std::valarray <T> atan2( const std::valarray <T>& y, const std::valarray <T>& x );
(1)
std::valarray <T> atan2( const std::valarray <T>& y, const std::valarray <T>& x );
template< class T >
(2)
std::valarray <T> atan2( const std::valarray <T>& y,
template< class T >
(3)
std::valarray <T> atan2( const typename std::valarray <T>::value_type& vy,
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.
[edit] Parameters
x, y
-
numeric arrays to compute inverse tangent of
vy, vx
-
values to compute inverse tangent of
[edit] Return value
A numeric array containing the results of computation of inverse tangent.
[edit] 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 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.
[edit] Example
Run this code
#include <algorithm> #include <cmath> #include <iomanip> #include <iostream> #include <valarray> void show(char const* title, const std::valarray <double>& va) { std::cout << title << ' '; std::for_each (std::begin (va), std::end (va), [](const double x) { std::cout << ' ' << std::right << std::setw (4) << x << "°"; }); std::cout << '\n'; } const double pi = std::acos (-1.0); // C++20: std::numbers::pi int main() { auto degrees_to_radians = [](double const& x) { return (pi * x / 180); }; auto radians_to_degrees = [](double const& x) { return (180 * x / pi); }; const std::valarray <double> degrees{-90, -60, -45, -30, 0, 30, 45, 60, 90}; const std::valarray <double> radians = degrees.apply(degrees_to_radians); const auto sin = std::sin (radians); const auto 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°
[edit] 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
|
[edit] See also
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