How to convert one variadic template to another variadic template?

Question

C++ / C#

How to convert one variadic templates into another, with a different number of parameters, according to a certain rule? (the code illustrates the problem)

struct A{
int i;
std::string s;
unsigned int u;
};
/*функция времени выполнения  что задаёт 
правило по преобразованию <А> в <int, std::string>
*/

template<typename Arg...>
struct Types;

auto types_new=foo<A,float,A>();//вернёт Types<int,std::string,float,int,std::string>

Answer 1

https://en.cppreference.com/w/cpp/utility/tuple/tu...
using this function, and a rule of the form:

//пользовательское
template<> constexpr auto Type_to<>(glm::vec3 vec){
    return std::tuple(vec.x,vec.y,vec.z);

//для любого типа
    template<typename T>
    constexpr auto Type_to(T value){
        return value;
    }
};

and writing a function of the form:

template<typename ...Arg>
    constexpr auto foo(){
        return  std::tuple_cat{std::make_tuple<Arg>...,""};
    }

you can get almost the desired result (there is one extra type at the end, but it's easy to remove it)