# std::exp(std::valarray)

< cpp‎ | numeric‎ | valarray
 Defined in header  template< class T > valarray exp( const valarray& va );

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

## Contents

### 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:

### Possible implementation

 template valarray exp(const valarray& va) { valarray other = va; for (T& i : other) i = exp(i);   return other; // proxy object may be returned }

### Example

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

#include <complex>
#include <iostream>
#include <numbers>
#include <valarray>

int main()
{
const double pi = std::numbers::pi;
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 (std::cout << std::showpos << std::fixed; auto n : v2)
std::cout << n << '\n';
}

Output:

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