c++14.cc

#include <array>
#include <iostream>
#include <tuple>
#include <utility>
#include <vector>

// Convert array into a tuple
template <typename Array, std::size_t... I>
decltype(auto) a2t_impl(const Array& a, std::index_sequence<I...>) {
  return std::make_tuple(a[I]...);
}

template <typename T, std::size_t N,
          typename Indices = std::make_index_sequence<N>>
decltype(auto) a2t(const std::array<T, N>& a) {
  return a2t_impl(a, Indices{});
}

// pretty-print a tuple

template <class Ch, class Tr, class Tuple, std::size_t... Is>
void print_tuple_impl(std::basic_ostream<Ch, Tr>& os, const Tuple& t,
                      std::index_sequence<Is...>) {
  ((os << (Is == 0 ? "" : ", ") << std::get<Is>(t)), ...);
}

template <class Ch, class Tr, class... Args>
decltype(auto) operator<<(std::basic_ostream<Ch, Tr>& os,
                          const std::tuple<Args...>& t) {
  os << "(";
  print_tuple_impl(os, t, std::index_sequence_for<Args...>{});
  return os << ")";
}

int main() {
  std::array<int, 4> array{{1, 2, 3, 4}};
  std::vector<int> ivec;

  // convert an array into a tuple
  auto tuple = a2t(array);
  static_assert(
      std::is_same<decltype(tuple), std::tuple<int, int, int, int>>::value, "");

  // print it to cout
  std::cout << tuple << '\n';
}