llvm-project/libcxx/include/mdspan

// -*-C++ - *-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===---------------------------------------------------------------------===//

/*

// Overall mdspan synopsis

namespace std {
  // [mdspan.extents], class template extents
  template<class IndexType, size_t... Extents>
    class extents;

  // [mdspan.extents.dextents], alias template dextents
  template<class IndexType, size_t Rank>
    using dextents = see below;

  // [mdspan.layout], layout mapping
  struct layout_left; // not implemented yet
  struct layout_right;
  struct layout_stride; // not implemented yet

  // [mdspan.accessor.default], class template default_accessor
  template<class ElementType>
    class default_accessor; // not implemented yet

  // [mdspan.mdspan], class template mdspan
  template<class ElementType, class Extents, class LayoutPolicy = layout_right,
           class AccessorPolicy = default_accessor<ElementType>>
    class mdspan; // not implemented yet
}

// extents synopsis

namespace std {
  template<class _IndexType, size_t... _Extents>
  class extents {
  public:
    using index_type = _IndexType;
    using size_type = make_unsigned_t<index_type>;
    using rank_type = size_t;

    // [mdspan.extents.obs], observers of the multidimensional index space
    static constexpr rank_type rank() noexcept { return sizeof...(_Extents); }
    static constexpr rank_type rank_dynamic() noexcept { return dynamic-index(rank()); }
    static constexpr size_t static_extent(rank_type) noexcept;
    constexpr index_type extent(rank_type) const noexcept;

    // [mdspan.extents.cons], constructors
    constexpr extents() noexcept = default;

    template<class _OtherIndexType, size_t... _OtherExtents>
      constexpr explicit(see below)
        extents(const extents<_OtherIndexType, _OtherExtents...>&) noexcept;
    template<class... _OtherIndexTypes>
      constexpr explicit extents(_OtherIndexTypes...) noexcept;
    template<class _OtherIndexType, size_t N>
      constexpr explicit(N != rank_dynamic())
        extents(span<_OtherIndexType, N>) noexcept;
    template<class _OtherIndexType, size_t N>
      constexpr explicit(N != rank_dynamic())
        extents(const array<_OtherIndexType, N>&) noexcept;

    // [mdspan.extents.cmp], comparison operators
    template<class _OtherIndexType, size_t... _OtherExtents>
      friend constexpr bool operator==(const extents&,
                                       const extents<_OtherIndexType, _OtherExtents...>&) noexcept;

  private:
    // libcxx note: we do not use an array here, but we need to preserve the as-if behavior
    // for example the default constructor must zero initialize dynamic extents
    array<index_type, rank_dynamic()> dynamic-extents{};                // exposition only
  };

  template<class... Integrals>
    explicit extents(Integrals...)
      -> see below;
}

// layout_right synopsis

namespace std {
  template<class Extents>
  class layout_right::mapping {
  public:
    using extents_type = Extents;
    using index_type = typename extents_type::index_type;
    using size_type = typename extents_type::size_type;
    using rank_type = typename extents_type::rank_type;
    using layout_type = layout_right;

    // [mdspan.layout.right.cons], constructors
    constexpr mapping() noexcept = default;
    constexpr mapping(const mapping&) noexcept = default;
    constexpr mapping(const extents_type&) noexcept;
    template<class OtherExtents>
      constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
        mapping(const mapping<OtherExtents>&) noexcept;
    template<class OtherExtents>
      constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
        mapping(const layout_left::mapping<OtherExtents>&) noexcept;
    template<class OtherExtents>
      constexpr explicit(extents_type::rank() > 0)
        mapping(const layout_stride::mapping<OtherExtents>&) noexcept;

    constexpr mapping& operator=(const mapping&) noexcept = default;

    // [mdspan.layout.right.obs], observers
    constexpr const extents_type& extents() const noexcept { return extents_; }

    constexpr index_type required_span_size() const noexcept;

    template<class... Indices>
      constexpr index_type operator()(Indices...) const noexcept;

    static constexpr bool is_always_unique() noexcept { return true; }
    static constexpr bool is_always_exhaustive() noexcept { return true; }
    static constexpr bool is_always_strided() noexcept { return true; }

    static constexpr bool is_unique() noexcept { return true; }
    static constexpr bool is_exhaustive() noexcept { return true; }
    static constexpr bool is_strided() noexcept { return true; }

    constexpr index_type stride(rank_type) const noexcept;

    template<class OtherExtents>
      friend constexpr bool operator==(const mapping&, const mapping<OtherExtents>&) noexcept;

  private:
    extents_type extents_{};    // exposition only
  };
}

*/

#ifndef _LIBCPP_MDSPAN
#define _LIBCPP_MDSPAN

#include <__config>
#include <__fwd/mdspan.h>
#include <__mdspan/extents.h>
#include <__mdspan/layout_right.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

#endif // _LIBCPP_MDSPAN