easy tuple on variadics

constexpr_tuple.cpp

#include <utility>
#include <cstdio>

template <typename ... Ts>
constexpr auto tuple(Ts&& ... ts)
{
    return [...ts = std::forward<Ts>(ts)](auto&& f) { return f(ts...);};
}

template <unsigned I, typename T, typename ... Ts>
constexpr auto get_val(const T& t, const Ts& ... ts)
{
   if constexpr (I == 0) return t;
   else return get_val<I-1>(ts...); 
}

template <unsigned I, typename T>
constexpr decltype(auto) get(T&& t)
{
    return t([](auto && ... vs){ return get_val<I>(std::forward<decltype(vs)>(vs)...);});
}

template <typename T>
constexpr auto size(T&& t)
{
    return t([](const auto& ... ts){ return sizeof...(ts);});
}

int main()
{
    constexpr auto t = tuple(1, "foo", 3.14);
    constexpr auto n = size(t);
    std::puts(get<1>(t));
    return get<n-1>(t) - get<0>(t);
}