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#ifndef TEMPLAT_UTIL_FLATTENTUPLE_H
#define TEMPLAT_UTIL_FLATTENTUPLE_H

/* This file is part of TempLat, available at https://cosmolattice.github.io/templat .
   Copyright 2021-2026 The TempLat authors, see AUTHORS.md.
   Released under the MIT license, see LICENSE.md. */

// File info: Main contributor(s): Adrien Florio, Year: 2019

#include <tuple>
#include <utility>

namespace TempLat
{

  // from https://stackoverflow.com/a/32166787
  // credit Piotr Skotnicki

  template <typename T> auto explode(T &&t, char) { return std::forward_as_tuple(std::forward<T>(t)); }

  template <typename T, std::size_t I = std::tuple_size<std::decay_t<T>>{}> auto explode(T &&t, int);

  template <typename T, std::size_t... Is> auto explode(T &&t, std::index_sequence<Is...>)
  {
    return std::tuple_cat(explode(std::get<Is>(std::forward<T>(t)), 0)...);
  }

  template <typename T, std::size_t I> auto explode(T &&t, int)
  {
    return explode(std::forward<T>(t), std::make_index_sequence<I>{});
  }

  template <typename T, std::size_t... Is> auto decay_tuple(T &&t, std::index_sequence<Is...>)
  {
    return std::make_tuple(std::get<Is>(std::forward<T>(t))...);
  }

  template <typename T> auto decay_tuple(T &&t)
  {
    return decay_tuple(std::forward<T>(t), std::make_index_sequence<std::tuple_size<std::decay_t<T>>{}>{});
  }

  // Changed the original name from merge_tuple to flattent_tuple.
  template <typename T, std::size_t... Is> auto flatten_tuple(T &&t, std::index_sequence<Is...>)
  {
    return decay_tuple(std::tuple_cat(explode(std::get<Is>(std::forward<T>(t)), 0)...));
  }

  template <typename T> auto flatten_tuple(T &&t)
  {
    return flatten_tuple(std::forward<T>(t), std::make_index_sequence<std::tuple_size<std::decay_t<T>>{}>{});
  }
} // namespace TempLat

#endif