function template

std::atan2

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

Compute atan2 of valarray elements

Returns a valarray containing the principal value of the arc tangent of all the elements, in the same order. The tangent for which it is calculated is the quotient of coordinates y/x, using their sign to determine the appropriate quadrant.

The function calls atan2 (unqualified) once for each element in both x and y; If either is a single T value, it is used for all calls.

This function overloads cmath's atan2.

Parameters

y: valarray or element with the y coordinate(s).
x: valarray or element with the x coordinate(s).

If both arguments are valarray objects and their sizes don't match, the behavior is undefined.

Return value

A valarray object with the arc tangent values of y/x.

Example

// atan2 valarray example
#include <iostream>     // std::cout
#include <cstddef>      // std::size_t
#include <cmath>        // std::atan2
#include <valarray>     // std::valarray, std::atan2

int main ()
{
  double y[] = {0.0, 3.0, -2.0};
  double x[] = {-3.0, 3.0, -1.0};
  std::valarray<double> ycoords (y,3);
  std::valarray<double> xcoords (x,3);

  std::valarray<double> results = atan2 (ycoords,xcoords);

  std::cout << "results:";
  for (std::size_t i=0; i<results.size(); ++i)
    std::cout << ' ' << results[i];
  std::cout << '\n';

  return 0;
}