Variadic templates

typedef function<double(double ...)> fun;
 
inline int sum() {
    return 0;
}
 
template <typename ... Types>
double sum(double a,Types ... args)
{
    return a+sum(args...);
}
 
int main(int argc, char** argv)
{
    fun f = sum; // 
    cout << sum(1, 2, 3, 4.1) << endl;
    system("pause");
    return 0;
}

#include <iostream>
#include <functional>
using namespace std;
 
template<typename ...Args>
using fun = function<double(Args...)>;
 
inline int sum() {
    return 0;
}
 
template <typename ... Types>
double sum(double a,Types ... args)
{
    return a+sum(args...);
}
 
int main(int argc, char** argv)
{
    fun<double,int,int,double> f = sum<int,int,double>;
    cout << f(1, 2, 3, 4.1) << endl;
   
    return 0;
}

#include <iostream>
#include <type_traits>
 
template <typename...Args>
std::common_type_t<Args...> summ(Args&&...args)
{
    std::common_type_t<Args...> s{};
    auto l={((s+=std::forward<Args>(args)),0)...};
    (void)l;
    return s;  
}
 
int main()
{
   std::cout << summ(1, 2, 3, 4.1) <<std::endl;
}

template <typename...Args>
constexpr auto summ(Args&&...args)
{
    return (std::forward<Args>(args) + ...);  
}

#include <iostream>
using namespace std;
 
inline double sum() {
    return 0.0;
}
 
template <typename T, typename ... Types>
double sum(T a,Types ... args)
{
    return a+sum(args...);
}
 
int main(int argc, char** argv)
{
    cout << sum(1, 2, 3, 4.1) << endl;  
    return 0;
}