setting typename default value for vardiac and normal template

Question

template<typename T, T... Xs> class Nzm
{
private:
template<typename... Ts> static constexpr T Max(Ts... xs);

template<typename Tx> static constexpr T Max(Tx x)
{
    return x;
}

template<typename T1, typename T2, typename... Ts> static constexpr T Max(T1 x, T2 y, Ts... xs)
{
    return y > x ? Max<T2, Ts...>(y, xs...) : Max<T1, Ts...>(x, xs...);
}

public:
static const T Z = Max(Xs...);
};


int main() {

static_assert(Nzm<int,1,2,3,4,5,6>::Z==5,"XYZ");

return 0;
}

I already know that all the typename are going to be int and I only want to use

Nzm<1,2,3,4,5,6> 

instead of

Nzm<int,1,2,3,4,5,6> 

this is for compile time execution no code or tips for making it runtime. is this possible? to set all this typename to int ?

Answer 1

The quick solution is to use a using declaration to get ride of the int.

template<int... x>
using helper =  Nzm<int, x...>;

int main() {

    static_assert(helper<1, 2, 3, 4, 5, 6>::Z == 6, "XYZ");

    return 0;
}

Another (better) way is to modify Nzm and replace all the typename templates with int templates. You're left with a redundancy between the parameters and template arguments, so you can get rid of the parameters.

template<int... Xs> class Nzm
{
private:
    template<int x> static constexpr int Max()
    {
        return x;
    }

    template<int x, int y, int... rest> static constexpr int Max()
    {
        return x > y ? Max<x, rest...>() : Max<y, rest...>();
    }

public:
    static const int Z = Max<Xs...>();
};

int main() {

    static_assert(Nzm<1, 2, 3, 4, 5, 6>::Z == 6, "XYZ");

    return 0;
}

Answer 2

If you want a template that accepts a parameter pack of int s, have yourself such a template:

template<int ...Is> class Nzm {
  // Your implementation follows
};

Templates can accept parameters which aren't types (among them parameters which are integers), and consequently they can accept analogous parameter packs.