File taglist.h

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#ifndef TEMPLAT_UTIL_RANGEITERATION_TAGLIST_H
#define TEMPLAT_UTIL_RANGEITERATION_TAGLIST_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 "TempLat/util/concat.h"
#include "TempLat/util/rangeiteration/tag.h"

namespace TempLat
{

  template <int... I> class TagListBase
  {
  public:
    // Put public methods here. These should change very little over time.
    TagListBase() : tags(std::make_tuple(Tag<I>()...)) {}

    // private:
    /* Put all member variables and private methods here. These may change arbitrarily. */

    std::tuple<Tag<I>...> tags;
  };

  // This comes from  http://spraetor.github.io/2016/01/02/template-integer-sequence.html
  // Unpack the TagList<T,N> in TagListBase<T,0,1,2,...> in Olog(N) compile time.

  template <int Start, int End> struct TagListHelper;

  template <int Start, int End> using MakeSeqImplTagList_t = typename TagListHelper<Start, End>::type;

  template <int N> using MakeSeqTagList_t = typename TagListHelper<0, N - 1>::type;

  template <int... I1s, int... I2s> struct Concat<TagListBase<I1s...>, TagListBase<I2s...>> {
    using type = TagListBase<I1s..., I2s...>;
  };

  template <int Start, int End> struct TagListHelper {
    using type =
        Concat_t<MakeSeqImplTagList_t<Start, (Start + End) / 2>, MakeSeqImplTagList_t<(Start + End) / 2 + 1, End>>;
  };

  // break condition:
  template <int I> struct TagListHelper<I, I> {
    using type = TagListBase<I>;
  };

  template <int START, int END> using TagList = typename TagListHelper<START, END>::type;

} // namespace TempLat

#endif