// Variadic template
template < int n >
class Vec
{
private:
    float e[n];
public:
    template <typename... Arguments>
    Vec(Arguments... params);
    constexpr int GetSize( void ) const { return n; }
};

template < int n >
template <typename... Arguments>
Vec<n>::Vec<n>(Arguments... params)
{
    static_assert(sizeof...(Arguments) == n, “size mismatch”);
    float v[] = { params... };
    for (int i = 0; i < n; ++i) {
        e[i] = v[i];
    }
}