From Jason Turner

[mdspan.layout.left]

C++23 → Trunk 4.6 KB 67 lines
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Archived: C++23
Markdown: C++23 | Trunk
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  1. tmp/tmpascidp4e/{from.md → to.md} +54 -5
tmp/tmpascidp4e/{from.md → to.md} RENAMED
@@ -9,13 +9,13 @@ stride 1, and strides increase left-to-right as the product of extents.
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  namespace std {
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  template<class Extents>
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  class layout_left::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_left;
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  // [mdspan.layout.left.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_right::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>&);
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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
@@ -94,11 +109,11 @@ 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 OtherExents>
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  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
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  mapping(const layout_right::mapping<OtherExtents>& other) noexcept;
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  ```
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  *Constraints:*
@@ -110,10 +125,44 @@ template<class OtherExents>
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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);
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  ```
@@ -165,11 +214,11 @@ is `true`. Equivalent to:
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  ``` cpp
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  return ((static_cast<index_type>(i) * stride(P)) + ... + 0);
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  ```
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  ``` cpp
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- constexpr index_type stride(rank_type i) const;
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  ```
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  *Constraints:* `extents_type::rank() > 0` is `true`.
174
 
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  *Preconditions:* `i < extents_type::rank()` is `true`.
 
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  namespace std {
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  template<class Extents>
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  class layout_left::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_left;
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  // [mdspan.layout.left.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_right::mapping<OtherExtents>&) noexcept;
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+ template<class LayoutLeftPaddedMapping>
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+ constexpr explicit(!is_convertible_v<typename LayoutLeftPaddedMapping::extents_type,
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+ extents_type>)
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+ mapping(const LayoutLeftPaddedMapping&) 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>&);
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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
 
109
 
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  *Effects:* Direct-non-list-initializes *extents\_* with
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  `other.extents()`.
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113
  ``` cpp
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+ template<class OtherExtents>
115
  constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
116
  mapping(const layout_right::mapping<OtherExtents>& other) noexcept;
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  ```
118
 
119
  *Constraints:*
 
125
  value of type `index_type` [[basic.fundamental]].
126
 
127
  *Effects:* Direct-non-list-initializes *extents\_* with
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  `other.extents()`.
129
 
130
+ ``` cpp
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+ template<class LayoutLeftPaddedMapping>
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+ constexpr explicit(!is_convertible_v<typename LayoutLeftPaddedMapping::extents_type,
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+ extents_type>)
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+ mapping(const LayoutLeftPaddedMapping&) noexcept;
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+ ```
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+
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+ *Constraints:*
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+
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+ - *`is-layout-left-padded-mapping-of`*`<LayoutLeftPaddedMapping>` is
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+ `true`.
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+ - `is_constructible_v<extents_type, typename LayoutLeftPaddedMapping::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(0)` does not equal `dynamic_extent`, and
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+ - `LayoutLeftPaddedMapping::`*`static-padding-stride`* does not equal
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+ `dynamic_extent`,
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+
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+ then `Extents::static_extent(0)` equals
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+ `LayoutLeftPaddedMapping::`*`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 `other.stride(1)` equals
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+ `other.extents().extent(0)`.
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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
165
  template<class OtherExtents>
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  constexpr explicit(extents_type::rank() > 0)
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  mapping(const layout_stride::mapping<OtherExtents>& other);
168
  ```
 
214
  ``` cpp
215
  return ((static_cast<index_type>(i) * stride(P)) + ... + 0);
216
  ```
217
 
218
  ``` cpp
219
+ constexpr index_type stride(rank_type i) const noexcept;
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  ```
221
 
222
  *Constraints:* `extents_type::rank() > 0` is `true`.
223
 
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  *Preconditions:* `i < extents_type::rank()` is `true`.