C++ tuple utils

tuple_tuils.cpp

#include <tuple>
#include <iostream>

template <typename Tuple, size_t ...xs>
constexpr auto sub_tuple(const Tuple &t, std::index_sequence<xs...>) {
  return std::make_tuple(std::get<xs>(t)...);
}

template <typename Tuple, size_t x, size_t ...xs>
constexpr auto sub_tail_tuple(const Tuple &t, std::index_sequence<x, xs...>) {
  return std::make_tuple(std::get<xs>(t)...);
}

template <typename Tuple>
constexpr auto tuple_head(const Tuple &t) {
  return std::get<0>(t);
}

template <typename Tuple>
constexpr auto tuple_last(const Tuple &t) {
  return std::get<std::tuple_size<Tuple>::value - 1>(t);
}

template <typename Tuple>
constexpr auto tuple_init(const Tuple &t) {
  constexpr size_t tuple_size = std::tuple_size<Tuple>::value;
  return sub_tuple(t, std::make_index_sequence<tuple_size - 1>());
}

template <typename Tuple>
constexpr auto tuple_tail(const Tuple &t) {
  constexpr size_t tuple_size = std::tuple_size<Tuple>::value;
  return sub_tail_tuple(t, std::make_index_sequence<tuple_size>());
}

int main() {
  std::tuple<int, double, std::string> tuple(1, 2.0, "abc");
  auto head = tuple_head(tuple);
  auto last = tuple_last(tuple);
  auto init = tuple_init(tuple);
  auto tail = tuple_tail(tuple);

  std::cout << "head : " << head << std::endl;
  std::cout << "last : " << last << std::endl;
  std::cout << "init : " << std::get<0>(init) << ", " << std::get<1>(init) << std::endl;
  std::cout << "tail : " << std::get<0>(tail) << ", " << std::get<1>(tail) << std::endl;
}