std::exp(std::valarray) (3) - Linux Manuals

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

NAME

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)