#include <cstddef>
#include <vector>
#include <type_traits>
#include <set>

/* Implement element_type */

int main()
{
    static_assert( std::is_same_v<element_type<float>::type, void> );
    static_assert( std::is_same_v<element_type<double*>::type, double> );
    static_assert( std::is_same_v<element_type<bool[5]>::type, bool> );
    static_assert( std::is_same_v<element_type<std::vector<int>>::type, int> );
    static_assert( std::is_same_v<element_type<std::set<char>>::type, char> );
}