From Jason Turner

[mdspan.layout.right]

C++23 → Trunk 4.3 KB 66 lines
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Archived: C++23
Markdown: C++23 | Trunk
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  1. tmp/tmpy30lajmv/{from.md → to.md} +55 -4
tmp/tmpy30lajmv/{from.md → to.md} RENAMED
@@ -9,13 +9,13 @@ stride 1, and strides increase right-to-left as the product of extents.
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  namespace std {
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  template<class Extents>
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  class layout_right::mapping {
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  public:
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  using extents_type = Extents;
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- using index_type = typename extents_type::index_type;
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- using size_type = typename extents_type::size_type;
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- using rank_type = typename extents_type::rank_type;
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  using layout_type = layout_right;
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  // [mdspan.layout.right.cons], constructors
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  constexpr mapping() noexcept = default;
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  constexpr mapping(const mapping&) noexcept = default;
@@ -24,10 +24,14 @@ namespace std {
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  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
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  mapping(const mapping<OtherExtents>&) noexcept;
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  template<class OtherExtents>
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  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
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  mapping(const layout_left::mapping<OtherExtents>&) noexcept;
 
 
 
 
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  template<class OtherExtents>
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  constexpr explicit(extents_type::rank() > 0)
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  mapping(const layout_stride::mapping<OtherExtents>&) noexcept;
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  constexpr mapping& operator=(const mapping&) noexcept = default;
@@ -53,10 +57,21 @@ namespace std {
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  template<class OtherExtents>
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  friend constexpr bool operator==(const mapping&, const mapping<OtherExtents>&) noexcept;
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  private:
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  extents_type extents_{}; // exposition only
 
 
 
 
 
 
 
 
 
 
 
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  };
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  }
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  ```
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  If `Extents` is not a specialization of `extents`, then the program is
@@ -110,10 +125,46 @@ template<class OtherExtents>
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  value of type `index_type` [[basic.fundamental]].
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  *Effects:* Direct-non-list-initializes *extents\_* with
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  `other.extents()`.
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  ``` cpp
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  template<class OtherExtents>
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  constexpr explicit(extents_type::rank() > 0)
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  mapping(const layout_stride::mapping<OtherExtents>& other) noexcept;
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  ```
@@ -133,11 +184,11 @@ template<class OtherExtents>
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  `other.extents()`.
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  ###### Observers <a id="mdspan.layout.right.obs">[[mdspan.layout.right.obs]]</a>
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  ``` cpp
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- index_type required_span_size() const noexcept;
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  ```
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  *Returns:* `extents().`*`fwd-prod-of-extents`*`(extents_type::rank())`.
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  ``` cpp
 
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  namespace std {
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  template<class Extents>
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  class layout_right::mapping {
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  public:
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  using extents_type = Extents;
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+ using index_type = extents_type::index_type;
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+ using size_type = extents_type::size_type;
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+ using rank_type = extents_type::rank_type;
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  using layout_type = layout_right;
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  // [mdspan.layout.right.cons], constructors
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  constexpr mapping() noexcept = default;
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  constexpr mapping(const mapping&) noexcept = default;
 
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  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
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  mapping(const mapping<OtherExtents>&) noexcept;
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  template<class OtherExtents>
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  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
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  mapping(const layout_left::mapping<OtherExtents>&) noexcept;
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+ template<class LayoutRightPaddedMapping>
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+ constexpr explicit(!is_convertible_v<typename LayoutRightPaddedMapping::extents_type,
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+ extents_type>)
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+ mapping(const LayoutRightPaddedMapping&) noexcept;
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  template<class OtherExtents>
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  constexpr explicit(extents_type::rank() > 0)
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  mapping(const layout_stride::mapping<OtherExtents>&) noexcept;
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  constexpr mapping& operator=(const mapping&) noexcept = default;
 
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  template<class OtherExtents>
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  friend constexpr bool operator==(const mapping&, const mapping<OtherExtents>&) noexcept;
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  private:
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  extents_type extents_{}; // exposition only
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+
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+ // [mdspan.sub.map], submdspan mapping specialization
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+ template<class... SliceSpecifiers>
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+ constexpr auto submdspan-mapping-impl(SliceSpecifiers...) const // exposition only
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+ -> see below;
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+
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+ template<class... SliceSpecifiers>
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+ friend constexpr auto submdspan_mapping(
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+ const mapping& src, SliceSpecifiers... slices) {
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+ return src.submdspan-mapping-impl(slices...);
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+ }
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  };
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  }
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  ```
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  If `Extents` is not a specialization of `extents`, then the program is
 
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  value of type `index_type` [[basic.fundamental]].
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  *Effects:* Direct-non-list-initializes *extents\_* with
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  `other.extents()`.
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+ ``` cpp
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+ template<class LayoutRightPaddedMapping>
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+ constexpr explicit(!is_convertible_v<typename LayoutRightPaddedMapping::extents_type,
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+ extents_type>)
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+ mapping(const LayoutRightPaddedMapping&) noexcept;
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+ ```
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+
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+ *Constraints:*
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+
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+ - *`is-layout-right-padded-mapping-of`*`<LayoutRightPaddedMapping>` is
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+ `true`.
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+ - `is_constructible_v<extents_type, typename LayoutRightPaddedMapping::extents_- type>`
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+ is `true`.
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+
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+ *Mandates:* If
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+
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+ - `Extents::rank()` is greater than one,
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+ - `Extents::static_extent(Extents::rank() - 1)` does not equal
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+ `dynamic_extent`, and
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+ - `LayoutRightPaddedMapping::`*`static-padding-stride`* does not equal
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+ `dynamic_extent`,
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+
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+ then `Extents::static_extent(Extents::rank() - 1)` equals
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+ `LayoutRightPaddedMapping::`*`static-padding-stride`*.
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+
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+ *Preconditions:*
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+
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+ - If `extents_type::rank() > 1` is `true`, then
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+ `other.stride(extents_type::rank() - 2)` equals
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+ `other.extents().extent(extents_type::rank() - 1)`.
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+ - `other.required_span_size()` is representable as a value of type
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+ `index_type`.
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+
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+ *Effects:* Direct-non-list-initializes `extents_` with
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+ `other.extents()`.
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+
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  ``` cpp
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  template<class OtherExtents>
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  constexpr explicit(extents_type::rank() > 0)
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  mapping(const layout_stride::mapping<OtherExtents>& other) noexcept;
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  ```
 
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  `other.extents()`.
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186
  ###### Observers <a id="mdspan.layout.right.obs">[[mdspan.layout.right.obs]]</a>
187
 
188
  ``` cpp
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+ constexpr index_type required_span_size() const noexcept;
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  ```
191
 
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  *Returns:* `extents().`*`fwd-prod-of-extents`*`(extents_type::rank())`.
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194
  ``` cpp