Std::exp(std::valarray) (3) Linux Manual Page

std::exp(std::valarray) – std::exp(std::valarray)

Synopsis

Defined in header<valarray>

    template <class T>

    valarray<T> exp(const valarray<T> &va);

For each element in va computes e raised to the power equal to the value of the element.

Parameters

va – value array to apply the operation to

Return value

Value array containing e raised by the values in va.

Notes

Unqualified function (exp) is used to perform the computation. If such function is not available, std::exp 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> exp( const valarray<T>& va )
  {
      valarray<T> other = va;
      for (T &i : other) {
          i = exp(i);
      }
      return other; // proxy object may be returned
  }

Example

This example demonstrates the Euler’s identity eiπ
= -1 and the related exponents.
// Run this code

#include <iostream>

#include <complex>

#include <valarray>
int main()

{
    const double pi = std::acos(-1);
    std::valarray<std::complex<double>> v = {
        {0, 0}, {0, pi / 2}, {0, pi}, {0, 3 * pi / 2}, {0, 2 * pi}};
    std::valarray<std::complex<double>> v2 = std::exp(v);
    for (auto n : v2) {
        std::cout << std::fixed << n << '\n';
    }
}

Output:

  (1.000000,0.000000)
  (0.000000,1.000000)
  (-1.000000,0.000000)
  (-0.000000,-1.000000)
  (1.000000,-0.000000)

std::exp(std::valarray) (3) Linux Manual Page