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include/preview/__mdspan/default_accessor.h

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+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_DEFAULT_ACCESSOR_H_
+#define PREVIEW_MDSPAN_DEFAULT_ACCESSOR_H_
+
+namespace preview {
+
+template<typename ElementType>
+struct default_accessor {
+
+};
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_DEFAULT_ACCESSOR_H_

include/preview/__mdspan/extents.h

@@ -0,0 +1,247 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_EXTENTS_H_
+#define PREVIEW_MDSPAN_EXTENTS_H_
+
+#include <array>
+#include <cassert>
+#include <cstddef>
+#include <limits>
+#include <type_traits>
+#include <utility>
+
+#include "preview/__span/dynamic_extent.h"
+#include "preview/__type_traits/bool_constant.h"
+#include "preview/__type_traits/conjunction.h"
+#include "preview/__type_traits/disjunction.h"
+#include "preview/__type_traits/negation.h"
+#include "preview/__utility/integer_sequence.h"
+
+namespace preview {
+namespace detail {
+
+// ---------- helpers ----------
+
+template<typename Seq1, typename Seq2>
+struct extents_same_dynamic_positions;
+
+template<std::size_t... I, std::size_t... J>
+struct extents_same_dynamic_positions<std::index_sequence<I...>, std::index_sequence<J...>>
+    : conjunction<bool_constant<(I == J) && (I == dynamic_extent)>...> {};
+
+template<typename Seq, typename Out = std::index_sequence<0>, std::size_t DRank = 0>
+struct extents_dynamic_index;
+
+template<std::size_t... DExtents, std::size_t DRank>
+struct extents_dynamic_index<std::index_sequence<>, std::index_sequence<DExtents...>, DRank> {
+  static constexpr std::size_t value[] = {DExtents...};
+};
+
+template<std::size_t Extent, std::size_t... Extents, std::size_t... DExtents, std::size_t DRank>
+struct extents_dynamic_index<std::index_sequence<Extent, Extents...>, std::index_sequence<DExtents...>, DRank>
+    : std::conditional_t<
+        (Extent == dynamic_extent),
+        extents_dynamic_index<std::index_sequence<Extents...>, std::index_sequence<DExtents..., DRank + 1>, DRank + 1>,
+        extents_dynamic_index<std::index_sequence<Extents...>, std::index_sequence<DExtents..., DRank>, DRank>
+    > {};
+
+template<typename Seq, typename Out = std::index_sequence<>, std::size_t Index = 0>
+struct extents_dynamic_index_inv;
+
+template<std::size_t... IndexInv, std::size_t Index>
+struct extents_dynamic_index_inv<std::index_sequence<>, std::index_sequence<IndexInv...>, Index> {
+  static constexpr std::size_t value[] = {IndexInv...};
+};
+
+template<std::size_t Extent, std::size_t... Extents, std::size_t... IndexInv, std::size_t Index>
+struct extents_dynamic_index_inv<std::index_sequence<Extent, Extents...>, std::index_sequence<IndexInv...>, Index>
+    : std::conditional_t<
+        (Extent == dynamic_extent),
+        extents_dynamic_index_inv<std::index_sequence<Extents...>, std::index_sequence<IndexInv..., Index>, Index + 1>,
+        extents_dynamic_index_inv<std::index_sequence<Extents...>, std::index_sequence<IndexInv...>, Index + 1>
+    > {};
+
+
+// ---------- extents_storage ----------
+
+template<typename IndexType, std::size_t RankDynamic /* > 0 */, std::size_t... Extents>
+struct extents_storage {
+  using rank_type = std::size_t;
+
+  constexpr extents_storage() noexcept = default;
+
+  template<typename OtherIndexType, std::size_t OtherRankDynamic, std::size_t... OtherExtents, std::enable_if_t<
+      extents_same_dynamic_positions<std::index_sequence<Extents...>, std::index_sequence<OtherExtents...>>
+  ::value, int> = 0>
+  constexpr extents_storage(const extents_storage<OtherIndexType, OtherRankDynamic, OtherExtents...>& other) noexcept
+      : dynamic_extents_(other.dynamic_extents_) {}
+
+  template<typename OtherIndexType, std::size_t OtherRankDynamic, std::size_t... OtherExtents, std::enable_if_t<
+      negation<extents_same_dynamic_positions<std::index_sequence<Extents...>, std::index_sequence<OtherExtents...>>>
+  ::value, int> = 0>
+  constexpr extents_storage(const extents_storage<OtherIndexType, OtherRankDynamic, OtherExtents...>& other) noexcept {
+    // Preconditions
+    assert(my_static_extent_is_equal_to_other_extent(other));
+
+    for (rank_type i = 0; i < RankDynamic; ++i) {
+      dynamic_extents_[i] = other.extent(dynamic_index_inv(i));
+    }
+  }
+
+  template<typename OtherIndexType, std::size_t... OtherExtents, std::enable_if_t<
+      negation<extents_same_dynamic_positions<std::index_sequence<Extents...>, std::index_sequence<OtherExtents...>>>
+  ::value, int> = 0>
+  constexpr extents_storage(const extents_storage<OtherIndexType, 0, OtherExtents...>& other) noexcept {
+    for (rank_type i = 0; i < RankDynamic; ++i) {
+      dynamic_extents_[i] = other.extent(dynamic_index_inv(i));
+    }
+  }
+
+  constexpr IndexType extent(rank_type i) const noexcept {
+    return kExtents[i] == dynamic_extent ? dynamic_extents_[dynamic_index(i)] : kExtents[i];
+  }
+  static constexpr rank_type dynamic_index(rank_type i) noexcept {
+    return dynamic_index_t::value[i];
+  }
+  static constexpr rank_type dynamic_index_inv(rank_type i) noexcept {
+    return dynamic_index_inv_t::value[i];
+  }
+
+ private:
+  using extents_sequence    = std::index_sequence<Extents...>;
+  using dynamic_index_t     = extents_dynamic_index<extents_sequence>;
+  using dynamic_index_inv_t = extents_dynamic_index_inv<extents_sequence>;
+
+  static constexpr rank_type   kRank           = sizeof...(Extents);
+  static constexpr std::size_t kExtents[kRank] = {Extents...};
+
+  template<typename Other>
+  constexpr bool my_static_extent_is_equal_to_other_extent(const Other& other) const noexcept {
+    for (rank_type r = 0; r < kRank; ++r) {
+      if (kExtents[r] != dynamic_extent && kExtents[r] != other.extent(r))
+        return false;
+    }
+    return true;
+  }
+
+  std::array<IndexType, RankDynamic> dynamic_extents_{};
+};
+
+template<typename IndexType, std::size_t... Extents>
+struct extents_storage<IndexType, 0, Extents...> {
+  using rank_type = std::size_t;
+
+  constexpr extents_storage() noexcept = default;
+
+  template<typename OtherIndexType, std::size_t RankDynamic, std::size_t... OtherExtents, std::enable_if_t<RankDynamic != 0, int> = 0>
+  constexpr extents_storage(const extents_storage<OtherIndexType, RankDynamic, OtherExtents...>& other) noexcept {
+    // Preconditions
+    assert(my_static_extent_is_equal_to_other_extent(other));
+  }
+
+  constexpr IndexType extent(rank_type i) const noexcept {
+    return kExtents[i];
+  }
+  static constexpr rank_type dynamic_index(rank_type) noexcept {
+    return 0;
+  }
+  static constexpr rank_type dynamic_index_inv(rank_type) noexcept {
+    assert(false);
+    return 0;
+  }
+
+ private:
+  static constexpr rank_type   kRank           = sizeof...(Extents);
+  static constexpr std::size_t kExtents[] = {Extents...};
+
+  template<typename Other>
+  constexpr bool my_static_extent_is_equal_to_other_extent(const Other& other) const noexcept {
+    for (rank_type r = 0; r < kRank; ++r) {
+      if (kExtents[r] != dynamic_extent && kExtents[r] != other.extent(r))
+        return false;
+    }
+    return true;
+  }
+};
+
+} // namespace detail
+
+template<typename IndexType, std::size_t... Extents>
+class extents
+    : public detail::extents_storage<
+        IndexType,
+        integer_sequence_count<std::index_sequence<Extents...>, dynamic_extent>::value,
+        Extents...>
+{
+  using storage_base = detail::extents_storage<
+      IndexType,
+      integer_sequence_count<std::index_sequence<Extents...>, dynamic_extent>::value,
+      Extents...>;
+
+  template<typename OtherIndexType, std::size_t... OtherExtents>
+  friend class extents;
+
+
+ public:
+  using index_type = IndexType;
+  using size_type = std::make_unsigned_t<index_type>;
+  using rank_type = std::size_t;
+
+  static constexpr rank_type rank() noexcept { return sizeof...(Extents); }
+  static constexpr rank_type rank_dynamic() noexcept { return storage_base::dynamic_index(rank()); }
+//  static constexpr std::size_t static_extent(rank_type r) noexcept {
+//
+//  }
+  constexpr index_type extent(rank_type i) const noexcept {
+    return storage_base::extent(i);
+  }
+
+  constexpr extents() noexcept = default;
+
+  template<typename OtherIndexType, std::size_t... OtherExtents, std::enable_if_t<conjunction<
+      bool_constant<sizeof...(OtherExtents) == rank()>,
+      bool_constant<(OtherExtents == dynamic_extent || Extents == dynamic_extent || OtherExtents == Extents)>...,
+      // explicit(false)
+      negation<disjunction<
+          bool_constant<(Extents != dynamic_extent) && (OtherExtents == dynamic_extent)>...,
+          bool_constant<(std::numeric_limits<index_type>::max() < std::numeric_limits<OtherIndexType>::max())>
+      >>
+  >::value, int> = 0>
+  constexpr extents(const extents<OtherIndexType, OtherExtents...>& other) noexcept
+      : storage_base(other) {}
+
+  template<typename OtherIndexType, std::size_t... OtherExtents, std::enable_if_t<conjunction<
+      bool_constant<sizeof...(OtherExtents) == rank()>,
+      bool_constant<(OtherExtents == dynamic_extent || Extents == dynamic_extent || OtherExtents == Extents)>...,
+      // explicit(true)
+      disjunction<
+          bool_constant<(Extents != dynamic_extent) && (OtherExtents == dynamic_extent)>...,
+          bool_constant<(std::numeric_limits<index_type>::max() < std::numeric_limits<OtherIndexType>::max())>
+      >
+  >::value, int> = 0>
+  constexpr explicit extents(const extents<OtherIndexType, OtherExtents...>& other) noexcept
+      : storage_base(other) {}
+
+  template<typename OtherIndexType, std::size_t... OtherExtents>
+  friend constexpr bool operator==(const extents& x, const extents<OtherIndexType, OtherExtents...>& y) noexcept {
+    if (decltype(x)::rank() != decltype(y)::rank())
+      return false;
+    for (rank_type r = 0; r < decltype(x)::rank(); ++r) {
+      if (x.extent(r) != y.extent(r))
+        return false;
+    }
+    return true;
+  }
+};
+
+//template<typename IndexType, std::size_t Rank>
+//using dextents;
+//
+//template<std::size_t Rank, class IndexType = std::size_t>
+//using dims = see below;
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_EXTENTS_H_

include/preview/__mdspan/full_extent.h

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+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_FULL_EXTENT_H_
+#define PREVIEW_MDSPAN_FULL_EXTENT_H_
+
+#include "preview/__core/inline_variable.h"
+
+namespace preview {
+
+struct full_extent_t {
+  explicit full_extent_t() = default;
+};
+
+PREVIEW_INLINE_VARIABLE constexpr full_extent_t full_extent{};
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_FULL_EXTENT_H_

include/preview/__mdspan/layout.h

@@ -0,0 +1,27 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_LAYOUT_H_
+#define PREVIEW_MDSPAN_LAYOUT_H_
+
+namespace preview {
+
+struct layout_left {
+  template<typename Extents>
+  struct mapping {};
+};
+
+struct layout_right {
+  template<typename Extents>
+  struct mapping {};
+};
+
+struct layout_stride {
+  template<typename Extents>
+  struct mapping {};
+};
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_LAYOUT_H_

include/preview/__mdspan/mdspan.h

@@ -0,0 +1,15 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_MDSPAN_H_
+#define PREVIEW_MDSPAN_MDSPAN_H_
+
+#include "preview/__mdspan/default_accessor.h"
+#include "preview/__mdspan/extents.h"
+
+namespace preview {
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_MDSPAN_H_

include/preview/__mdspan/strided_slice.h

@@ -0,0 +1,12 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_STRIDED_SLICE_H_
+#define PREVIEW_MDSPAN_STRIDED_SLICE_H_
+
+namespace preview {
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_STRIDED_SLICE_H_

include/preview/__mdspan/submdspan_mapping_result.h

@@ -0,0 +1,12 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_SUBMDSPAN_SLICE_RESULT_H_
+#define PREVIEW_MDSPAN_SUBMDSPAN_SLICE_RESULT_H_
+
+namespace preview {
+
+} // namespace preview
+
+#endif // PREVIEW_MDSPAN_SUBMDSPAN_SLICE_RESULT_H_

include/preview/mdspan.h

@@ -0,0 +1,14 @@
+//
+// Created by yonggyulee on 2024. 9. 27.
+//
+
+#ifndef PREVIEW_MDSPAN_H_
+#define PREVIEW_MDSPAN_H_
+
+#include "preview/__mdspan/full_extent.h"
+#include "preview/__mdspan/layout.h"
+#include "preview/__mdspan/mdspan.h"
+#include "preview/__mdspan/strided_slice.h"
+#include "preview/__mdspan/submdspan_mapping_result.h"
+
+#endif // PREVIEW_MDSPAN_H_