std::exp(std::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

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

#include <iostream>
#include <complex>
#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';
    }
}

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

See also