< cpp‎ | numeric‎ | valarray
Revision as of 22:21, 31 May 2013 by P12bot (Talk | contribs)

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.



va - value array to apply the operation to

Return value

Value array containing e raised by the values in va.


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++14) 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


This example demonstrates the Euler's identity e
= -1
and the related exponents.

#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';



See also

returns e raised to the given power (ex)
(function) [edit]
complex base e exponential
(function template) [edit]