标准库标头 <mdspan> (C++23)

 

C++

编译器支持

自立实现与有宿主实现

语言

标准库

标准库标头

具名要求

功能特性测试宏(C++20)

语言支持库

概念库(C++20)

诊断库

内存管理库

元编程库(C++11)

通用工具库

容器库

迭代器库

范围库(C++20)

算法库

字符串库

文本处理库

数值库

日期和时间库

输入/输出库

文件系统库(C++17)

并发支持库(C++11)

执行控制库(C++26)

技术规范

符号索引

外部库

 

标准库头

语言支持 <cfloat> <climits> <compare>(C++20) <contracts>(C++26) <coroutine>(C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint>(C++11) <cstdlib> <exception> <initializer_list>(C++11)    <limits> <new> <source_location>(C++20) <stdfloat>(C++23) <typeinfo> <version>(C++20) 概念 <concepts>(C++20) 诊断 <cassert> <cerrno> <debugging>(C++26) <stacktrace>(C++23) <stdexcept> <system_error>(C++11) 内存管理 <memory> <memory_resource>(C++17) <scoped_allocator>(C++11) 元编程 <type_traits>(C++11) <ratio>(C++11)

通用工具 <any>(C++17) <bitset> <bit>(C++20) <charconv>(C++17) <expected>(C++23) <format>(C++20) <functional> <optional>(C++17) <stdbit.h>(C++26) <tuple>(C++11) <typeindex>(C++11) <utility> <variant>(C++17) 容器 <array>(C++11) <deque> <flat_map>(C++23) <flat_set>(C++23) <forward_list>(C++11) <hive>(C++26) <inplace_vector>(C++26)    <list> <map> <mdspan>(C++23) <queue> <set> <span>(C++20) <stack> <unordered_map>(C++11) <unordered_set>(C++11) <vector> 迭代器 <iterator> 范围 <generator>(C++23) <ranges>(C++20)

算法 <algorithm> <numeric> 字符串 <cctype> <cstring> <cuchar>(C++11) <cwchar> <cwctype> <string_view>(C++17) <string> 文本处理 <clocale> <codecvt>(C++11/17/26*) <locale> <regex>(C++11) <text_encoding>(C++26)    cpp/header#数值库数值 <cfenv>(C++11) <cmath> <complex> <linalg>(C++26) <numbers>(C++20) <random>(C++11) <simd>(C++26) <stdckdint.h>(C++26) <valarray> 时间 <chrono>(C++11) <ctime> C 兼容性 <ccomplex>(C++11/17/20*) <ciso646>(C++20 前) <cstdalign>(C++11/17/20*) <cstdbool>(C++11/17/20*) <ctgmath>(C++11/17/20*)

输入/输出 <cinttypes>(C++11) <cstdio> <filesystem>(C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print>(C++23) <spanstream>(C++23) <sstream> <streambuf> <strstream>(C++98/26*) <syncstream>(C++20) 并发支持 <atomic>(C++11) <barrier>(C++20) <condition_variable>(C++11) <future>(C++11) <hazard_pointer>(C++26) <latch>(C++20) <mutex>(C++11) <rcu>(C++26) <semaphore>(C++20) <shared_mutex>(C++14) <stdatomic.h>(C++23) <stop_token>(C++20) <thread>(C++11) 执行支持 <execution>(C++17)

 

此头文件是容器库的一部分。

类
mdspan (C++23)	多维非拥有数组视图 (类模板)
extents (C++23)	某秩多维索引空间的一个描述符 (类模板)
layout_left (C++23)	列优先多维数组布局映射策略；最左边的尺度具有步幅 1 (类)
layout_right (C++23)	行优先多维数组布局映射策略；最右边的尺度具有步幅 1 (类)
layout_stride (C++23)	具有用户自定义步长的布局映射策略 (类)
layout_left_padded (C++26)	具有可大于或等于最左侧尺度的填充跨步的列主序布局映射策略 (类)
layout_right_padded (C++26)	具有可大于或等于最右侧尺度的填充跨步的行主序布局映射策略 (类)
default_accessor (C++23)	指示索引访问 mdspan 元素的方式的类型 (类模板)
strided_slice (C++26)	切片说明符，表示一组按照偏移量、尺度和跨步三值指定的有规律分布的索引 (类模板)
submdspan_mapping_result (C++26)	各 submdspan_mapping 重载的返回类型 (类模板)
别名模板
dextentsdims (C++23)(C++26)	全动态 std::extents 的方便别名模板 (别名模板)
函数
submdspan_extents (C++26)	从现存 extents 和分片说明符创建新的 extents (函数模板)
submdspan (C++26)	返回现存 mdspan 的子集上的视图 (函数模板)
标签
full_extentfull_extent_t (C++26)	切片说明符标签，描述指定尺度的全部索引范围。 (标签)

概要

// 全部独立namespace std {// 类模板 extentstemplate<class IndexType, size_t... Extents>class extents;   // 别名模板 dextentstemplate<class IndexType, size_t Rank>using dextents =/* 见描述 */;   // 别名模板 dimstemplate<size_t Rank, class IndexType = size_t>using dims =/* 见描述 */;   // 布局映射struct layout_left;struct layout_right;struct layout_stride;template<size_t PaddingValue = dynamic_extent>struct layout_left_padded;template<size_t PaddingValue = dynamic_extent>struct layout_right_padded;   // 类模板 default_accessortemplate<class ElementType>class default_accessor;   // 类模板 mdspantemplate<class ElementType, class Extents, class LayoutPolicy = layout_right, class AccessorPolicy = default_accessor<ElementType>>class mdspan;   // 创建 submdspantemplate<class OffsetType, class LengthType, class StrideType>struct strided_slice;   template<class LayoutMapping>struct submdspan_mapping_result;   struct full_extent_t {explicit full_extent_t()=default;};inlineconstexpr full_extent_t full_extent{};   template<class IndexType, class... Extents, class... SliceSpecifiers>constexprauto submdspan_extents(const extents<IndexType, Extents...>&, SliceSpecifiers...);   // 函数模板 submdspantemplate<class ElementType, class Extents, class LayoutPolicy, class AccessorPolicy, class... SliceSpecifiers>constexprauto submdspan(const mdspan<ElementType, Extents, LayoutPolicy, AccessorPolicy>& src, SliceSpecifiers... slices)->/* 见描述 */;   template<class T, class IndexType> concept /*index-pair-like*/=// 仅用于阐释/*pair-like*/<T>&& convertible_to<tuple_element_t<0, T>, IndexType>&& convertible_to<tuple_element_t<1, T>, IndexType>;}

类模板 std::mdspan

namespace std {template<class ElementType, class Extents, class LayoutPolicy = layout_right, class AccessorPolicy = default_accessor<ElementType>>class mdspan {public:using extents_type = Extents;using layout_type = LayoutPolicy;using accessor_type = AccessorPolicy;using mapping_type =typename layout_type::template mapping<extents_type>;using element_type = ElementType;using value_type = remove_cv_t<element_type>;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 data_handle_type =typename accessor_type::data_handle_type;using reference =typename accessor_type::reference;   staticconstexpr rank_type rank()noexcept{return extents_type::rank();}staticconstexpr rank_type rank_dynamic()noexcept{return extents_type::rank_dynamic();}staticconstexpr size_t static_extent(rank_type r)noexcept{return extents_type::static_extent(r);}constexpr index_type extent(rank_type r)constnoexcept{return extents().extent(r);}   // 构造函数constexpr mdspan();constexpr mdspan(const mdspan& rhs)=default;constexpr mdspan(mdspan&& rhs)=default;   template<class... OtherIndexTypes>constexprexplicit mdspan(data_handle_type ptr, OtherIndexTypes... exts);template<class OtherIndexType, size_t N>constexprexplicit(N != rank_dynamic()) mdspan(data_handle_type p, span<OtherIndexType, N> exts);template<class OtherIndexType, size_t N>constexprexplicit(N != rank_dynamic()) mdspan(data_handle_type p, const array<OtherIndexType, N>& exts);constexpr mdspan(data_handle_type p, const extents_type& ext);constexpr mdspan(data_handle_type p, const mapping_type& m);constexpr mdspan(data_handle_type p, const mapping_type& m, const accessor_type& a);   template<class OtherElementType, class OtherExtents, class OtherLayoutPolicy, class OtherAccessorPolicy>constexprexplicit(/* 见描述 */) mdspan(const mdspan<OtherElementType, OtherExtents, OtherLayoutPolicy, OtherAccessorPolicy>& other);   constexpr mdspan& operator=(const mdspan& rhs)=default;constexpr mdspan& operator=(mdspan&& rhs)=default;   // 成员template<class... OtherIndexTypes>constexpr reference operator[](OtherIndexTypes... indices)const;template<class OtherIndexType>constexpr reference operator[](span<OtherIndexType, rank()> indices)const;template<class OtherIndexType>constexpr reference operator[](const array<OtherIndexType, rank()>& indices)const;   constexpr size_type size()constnoexcept;constexprbool empty()constnoexcept;   friendconstexprvoid swap(mdspan& x, mdspan& y)noexcept;   constexprconst extents_type& extents()constnoexcept{return/*map_*/.extents();}constexprconst data_handle_type& data_handle()constnoexcept{return/*ptr_*/;}constexprconst mapping_type& mapping()constnoexcept{return/*map_*/;}constexprconst accessor_type& accessor()constnoexcept{return/*acc_*/;}   staticconstexprbool is_always_unique(){return mapping_type::is_always_unique();}staticconstexprbool is_always_exhaustive(){return mapping_type::is_always_exhaustive();}staticconstexprbool is_always_strided(){return mapping_type::is_always_strided();}   constexprbool is_unique()const{return/*map_*/.is_unique();}constexprbool is_exhaustive()const{return/*map_*/.is_exhaustive();}constexprbool is_strided()const{return/*map_*/.is_strided();}constexpr index_type stride(rank_type r)const{return/*map_*/.stride(r);}   private: accessor_type /*acc_*/;// 仅用于阐释 mapping_type /*map_*/;// 仅用于阐释 data_handle_type /*ptr_*/;// 仅用于阐释};   template<class CArray> requires(is_array_v<CArray>&& rank_v<CArray>==1) mdspan(CArray&)-> mdspan<remove_all_extents_t<CArray>, extents<size_t, extent_v<CArray, 0>>>;   template<class Pointer> requires(is_pointer_v<remove_reference_t<Pointer>>) mdspan(Pointer&&)-> mdspan<remove_pointer_t<remove_reference_t<Pointer>>, extents<size_t>>;   template<class ElementType, class... Integrals> requires((is_convertible_v<Integrals, size_t>&& ...)&& sizeof...(Integrals)>0)explicit mdspan(ElementType*, Integrals...)-> mdspan<ElementType, extents<size_t, /*maybe-static-ext*/<Integrals>...>>;   template<class ElementType, class OtherIndexType, size_t N> mdspan(ElementType*, span<OtherIndexType, N>)-> mdspan<ElementType, dextents<size_t, N>>;   template<class ElementType, class OtherIndexType, size_t N> mdspan(ElementType*, const array<OtherIndexType, N>&)-> mdspan<ElementType, dextents<size_t, N>>;   template<class ElementType, class IndexType, size_t... ExtentsPack> mdspan(ElementType*, const extents<IndexType, ExtentsPack...>&)-> mdspan<ElementType, extents<IndexType, ExtentsPack...>>;   template<class ElementType, class MappingType> mdspan(ElementType*, const MappingType&)-> mdspan<ElementType, typename MappingType::extents_type, typename MappingType::layout_type>;   template<class MappingType, class AccessorType> mdspan(consttypename AccessorType::data_handle_type&, const MappingType&, const AccessorType&)-> mdspan<typename AccessorType::element_type, typename MappingType::extents_type, typename MappingType::layout_type, AccessorType>;}

类模板 std::extents

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;   // 多维索引空间的观察器staticconstexpr rank_type rank()noexcept{return sizeof...(Extents);}staticconstexpr rank_type rank_dynamic()noexcept{return/*dynamic-index*/(rank());}staticconstexpr size_t static_extent(rank_type)noexcept;constexpr index_type extent(rank_type)constnoexcept;   // 构造函数constexpr extents()noexcept=default;   template<class OtherIndexType, size_t... OtherExtents>constexprexplicit(/* 见描述 */) extents(const extents<OtherIndexType, OtherExtents...>&)noexcept;template<class... OtherIndexTypes>constexprexplicit extents(OtherIndexTypes...)noexcept;template<class OtherIndexType, size_t N>constexprexplicit(N != rank_dynamic()) extents(span<OtherIndexType, N>)noexcept;template<class OtherIndexType, size_t N>constexprexplicit(N != rank_dynamic()) extents(const array<OtherIndexType, N>&)noexcept;   // 比较运算符template<class OtherIndexType, size_t... OtherExtents>friendconstexprbool operator==(const extents&, const extents<OtherIndexType, OtherExtents...>&)noexcept;   // 仅用于阐释的辅助工具constexpr size_t /*fwd-prod-of-extents*/(rank_type)constnoexcept;// 仅用于阐释constexpr size_t /*rev-prod-of-extents*/(rank_type)constnoexcept;// 仅用于阐释template<class OtherIndexType>staticconstexprauto/*index-cast*/(OtherIndexType&&)noexcept;// 仅用于阐释   private:staticconstexpr rank_type /*dynamic-index*/(rank_type)noexcept;// 仅用于阐释staticconstexpr rank_type /*dynamic-index-inv*/( rank_type)noexcept;// 仅用于阐释 array<index_type, rank_dynamic()>/*dynamic-extents*/{};// 仅用于阐释};   template<class... Integrals>explicit extents(Integrals...)->/* 见描述 */;}

布局映射策略

namespace std {struct layout_left {template<class Extents>class mapping;};struct layout_right {template<class Extents>class mapping;};struct layout_stride {template<class Extents>class mapping;};   template<size_t PaddingValue>struct layout_left_padded {template<class Extents>class mapping;};template<size_t PaddingValue>struct layout_right_padded {template<class Extents>class mapping;};}

类模板 std::layout_left::mapping

namespace std {template<class Extents>class layout_left::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_left;   // 构造函数constexpr mapping()noexcept=default;constexpr mapping(const mapping&)noexcept=default;constexpr mapping(const extents_type&)noexcept;template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const mapping<OtherExtents>&)noexcept;template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_right::mapping<OtherExtents>&)noexcept;template<class LayoutLeftPaddedMapping>constexprexplicit(!is_convertible_v<typename LayoutLeftPaddedMapping::extents_type, extents_type>) mapping(const LayoutLeftPaddedMapping&)noexcept;template<class OtherExtents>constexprexplicit(extents_type::rank()>0) mapping(const layout_stride::mapping<OtherExtents>&);   constexpr mapping& operator=(const mapping&)noexcept=default;   // 观察器constexprconst extents_type& extents()constnoexcept{return/*extents_*/;}   constexpr index_type required_span_size()constnoexcept;   template<class... Indices>constexpr index_type operator()(Indices...)constnoexcept;   staticconstexprbool is_always_unique()noexcept{returntrue;}staticconstexprbool is_always_exhaustive()noexcept{returntrue;}staticconstexprbool is_always_strided()noexcept{returntrue;}   staticconstexprbool is_unique()noexcept{returntrue;}staticconstexprbool is_exhaustive()noexcept{returntrue;}staticconstexprbool is_strided()noexcept{returntrue;}   constexpr index_type stride(rank_type)constnoexcept;   template<class OtherExtents>friendconstexprbool operator==(const mapping&, const mapping<OtherExtents>&)noexcept;   private: extents_type /*extents_*/{};// 仅用于阐释   // submdspan 映射的特化template<class... SliceSpecifiers>constexprauto/*submdspan-mapping-impl*/(SliceSpecifiers...)const// 仅用于阐释->/* 见描述 */;   template<class... SliceSpecifiers>friendconstexprauto submdspan_mapping(const mapping& src, SliceSpecifiers... slices){return src./*submdspan-mapping-impl*/(slices...);}};}

类模板 std::layout_right::mapping

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;   // 构造函数constexpr mapping()noexcept=default;constexpr mapping(const mapping&)noexcept=default;constexpr mapping(const extents_type&)noexcept;template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const mapping<OtherExtents>&)noexcept;template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_left::mapping<OtherExtents>&)noexcept;template<class LayoutRightPaddedMapping>constexprexplicit(!is_convertible_v<typename LayoutRightPaddedMapping::extents_type, extents_type>) mapping(const LayoutRightPaddedMapping&)noexcept;template<class OtherExtents>constexprexplicit(extents_type::rank()>0) mapping(const layout_stride::mapping<OtherExtents>&)noexcept;   constexpr mapping& operator=(const mapping&)noexcept=default;   // 观察器constexprconst extents_type& extents()constnoexcept{return/*extents_*/;}   constexpr index_type required_span_size()constnoexcept;   template<class... Indices>constexpr index_type operator()(Indices...)constnoexcept;   staticconstexprbool is_always_unique()noexcept{returntrue;}staticconstexprbool is_always_exhaustive()noexcept{returntrue;}staticconstexprbool is_always_strided()noexcept{returntrue;}   staticconstexprbool is_unique()noexcept{returntrue;}staticconstexprbool is_exhaustive()noexcept{returntrue;}staticconstexprbool is_strided()noexcept{returntrue;}   constexpr index_type stride(rank_type)constnoexcept;   template<class OtherExtents>friendconstexprbool operator==(const mapping&, const mapping<OtherExtents>&)noexcept;   private: extents_type /*extents_*/{};// 仅用于阐释   // submdspan 映射的特化template<class... SliceSpecifiers>constexprauto/*submdspan-mapping-impl*/(SliceSpecifiers...)const// 仅用于阐释->/* 见描述 */;   template<class... SliceSpecifiers>friendconstexprauto submdspan_mapping(const mapping& src, SliceSpecifiers... slices){return src./*submdspan-mapping-impl*/(slices...);}};}

类模板 std::layout_stride::mapping

namespace std {template<class Extents>class layout_stride::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_stride;   private:staticconstexpr rank_type /*rank_*/= extents_type::rank();// 仅用于阐释   public:// 构造函数constexpr mapping()noexcept;constexpr mapping(const mapping&)noexcept=default;template<class OtherIndexType>constexpr mapping(const extents_type&, span<OtherIndexType, /*rank_*/>)noexcept;template<class OtherIndexType>constexpr mapping(const extents_type&, const array<OtherIndexType, /*rank_*/>&)noexcept;   template<class StridedLayoutMapping>constexprexplicit(/* 见描述 */) mapping(const StridedLayoutMapping&)noexcept;   constexpr mapping& operator=(const mapping&)noexcept=default;   // 观察器constexprconst extents_type& extents()constnoexcept{return/*extents_*/;}constexpr array<index_type, /*rank_*/> strides()constnoexcept{return/*strides_*/;}   constexpr index_type required_span_size()constnoexcept;   template<class... Indices>constexpr index_type operator()(Indices...)constnoexcept;   staticconstexprbool is_always_unique()noexcept{returntrue;}staticconstexprbool is_always_exhaustive()noexcept{returnfalse;}staticconstexprbool is_always_strided()noexcept{returntrue;}   staticconstexprbool is_unique()noexcept{returntrue;}constexprbool is_exhaustive()constnoexcept;staticconstexprbool is_strided()noexcept{returntrue;}   constexpr index_type stride(rank_type i)constnoexcept{return/*strides_*/[i];}   template<class OtherMapping>friendconstexprbool operator==(const mapping&, const OtherMapping&)noexcept;   private: extents_type /*extents_*/{};// 仅用于阐释 array<index_type, /*rank_*/>/*strides_*/{};// 仅用于阐释   // submdspan 映射的特化template<class... SliceSpecifiers>constexprauto/*submdspan-mapping-impl*/(SliceSpecifiers...)const// 仅用于阐释->/* 见描述 */;   template<class... SliceSpecifiers>friendconstexprauto submdspan_mapping(const mapping& src, SliceSpecifiers... slices){return src./*submdspan-mapping-impl*/(slices...);}};}

类模板 std::layout_left_padded::mapping

namespace std {template<size_t PaddingValue>template<class Extents>class layout_left_padded<PaddingValue>::mapping{public:staticconstexpr size_t padding_value = PaddingValue;   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_left_padded<PaddingValue>;   private:staticconstexpr size_t /*rank_*/= extents_type::rank();// 仅用于阐释staticconstexpr size_t /*first-static-extent*/=// 仅用于阐释 extents_type::static_extent(0);   // 仅用于阐释的成员staticconstexpr size_t /*static-padding-stride*/=/* 见描述 */;// 仅用于阐释   public:// 构造函数constexpr mapping()noexcept: mapping(extents_type{}){}constexpr mapping(const mapping&)noexcept=default;constexpr mapping(const extents_type&);template<class OtherIndexType>constexpr mapping(const extents_type&, OtherIndexType);template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_left::mapping<OtherExtents>&);template<class OtherExtents>constexprexplicit(extents_type::rank()>0) mapping(const layout_stride::mapping<OtherExtents>&);template<class LayoutLeftPaddedMapping>constexprexplicit(/* 见描述 */) mapping(const LayoutLeftPaddedMapping&);template<class LayoutRightPaddedMapping>constexprexplicit(/* 见描述 */) mapping(const LayoutRightPaddedMapping&)noexcept;   constexpr mapping& operator=(const mapping&)noexcept=default;   // 观察器constexprconst extents_type& extents()constnoexcept{return/*extents_*/;}constexpr array<index_type, rank_> strides()constnoexcept;   constexpr index_type required_span_size()constnoexcept;template<class... Indices>constexpr index_type operator()(Indices...)constnoexcept;   staticconstexprbool is_always_unique()noexcept{returntrue;}staticconstexprbool is_always_exhaustive()noexcept;staticconstexprbool is_always_strided()noexcept{returntrue;}   staticconstexprbool is_unique()noexcept{returntrue;}constexprbool is_exhaustive()constnoexcept;staticconstexprbool is_strided()noexcept{returntrue;}   constexpr index_type stride(rank_type)constnoexcept;   template<class LayoutLeftPaddedMapping>friendconstexprbool operator==(const mapping&, const LayoutLeftPaddedMapping&)noexcept;   private:// 仅用于阐释的成员 index_type /*stride-1*/=/*static-padding-stride*/;// 仅用于阐释 extents_type /*extents_*/{};// 仅用于阐释// submdspan 映射的特化template<class... SliceSpecifiers>constexprauto/*submdspan-mapping-impl*/(SliceSpecifiers...)const// 仅用于阐释->/* 见描述 */;   template<class... SliceSpecifiers>friendconstexprauto submdspan_mapping(const mapping& src, SliceSpecifiers... slices){return src./*submdspan-mapping-impl*/(slices...);}};}

类模板 std::layout_right_padded::mapping

namespace std {template<size_t PaddingValue>template<class Extents>class layout_right_padded<PaddingValue>::mapping{public:staticconstexpr size_t padding_value = PaddingValue;   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_padded<PaddingValue>;   private:staticconstexpr size_t /*rank_*/= extents_type::rank();// 仅用于阐释staticconstexpr size_t /*last-static-extent*/=// 仅用于阐释 extents_type::static_extent(/*rank_*/-1);   // 仅用于阐释的成员staticconstexpr size_t /*static-padding-stride*/=/* 见描述 */;// 仅用于阐释   public:// 构造函数constexpr mapping()noexcept: mapping(extents_type{}){}constexpr mapping(const mapping&)noexcept=default;constexpr mapping(const extents_type&);template<class OtherIndexType>constexpr mapping(const extents_type&, OtherIndexType);   template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_right::mapping<OtherExtents>&);template<class OtherExtents>constexprexplicit(rank_ >0) mapping(const layout_stride::mapping<OtherExtents>&);template<class LayoutRightPaddedMapping>constexprexplicit(/* 见描述 */) mapping(const LayoutRightPaddedMapping&);template<class LayoutLeftPaddedMapping>constexprexplicit(/* 见描述 */) mapping(const LayoutLeftPaddedMapping&)noexcept;   constexpr mapping& operator=(const mapping&)noexcept=default;   // 观察器constexprconst extents_type& extents()constnoexcept{return extents_;}constexpr array<index_type, rank_> strides()constnoexcept;   constexpr index_type required_span_size()constnoexcept;   template<class... Indices>constexpr index_type operator()(Indices...)constnoexcept;   staticconstexprbool is_always_unique()noexcept{returntrue;}staticconstexprbool is_always_exhaustive()noexcept;staticconstexprbool is_always_strided()noexcept{returntrue;}   staticconstexprbool is_unique()noexcept{returntrue;}constexprbool is_exhaustive()constnoexcept;staticconstexprbool is_strided()noexcept{returntrue;}   constexpr index_type stride(rank_type)constnoexcept;   template<class LayoutRightPaddedMapping>friendconstexprbool operator==(const mapping&, const LayoutRightPaddedMapping&)noexcept;   private:// 仅用于阐释的成员 index_type /*stride-rm2*/=/*static-padding-stride*/;// 仅用于阐释 extents_type /*extents_*/{};// 仅用于阐释   // submdspan 映射的特化template<class... SliceSpecifiers>constexprauto/*submdspan-mapping-impl*/(SliceSpecifiers...)const// 仅用于阐释->/* 见描述 */;   template<class... SliceSpecifiers>friendconstexprauto submdspan_mapping(const mapping& src, SliceSpecifiers... slices){return src./*submdspan-mapping-impl*/(slices...);}};}

仅用于阐释的辅助工具

template<class T>constexprbool/*is-extents*/=false;// 仅用于阐释template<class IndexType, size_t... Args>constexprbool/*is-extents*/<extents<IndexType, Args...>>=true;// 仅用于阐释   template<class M> concept /*layout-mapping-alike*/= requires {// 仅用于阐释 requires /*is-extents*/<typename M::extents_type>;{ M::is_always_strided()}-> same_as<bool>;{ M::is_always_exhaustive()}-> same_as<bool>;{ M::is_always_unique()}-> same_as<bool>; bool_constant<M::is_always_strided()>::value; bool_constant<M::is_always_exhaustive()>::value; bool_constant<M::is_always_unique()>::value;};   template<class T>constexpr T /*de-ice*/(T val){return val;}template</*integral-constant-like*/ T>constexprauto/*de-ice*/(T){return T::value;}   template<class IndexType, size_t k, class... SliceSpecifiers>constexpr IndexType /*first_*/(SliceSpecifiers... slices);   template<size_t k, class Extents, class... SliceSpecifiers>constexprauto/*last_*/(const Extents& src, SliceSpecifiers... slices);   template<class IndexType, size_t N, class... SliceSpecifiers>constexpr array<IndexType, sizeof...(SliceSpecifiers)>/*src-indices*/(const array<IndexType, N>& indices, SliceSpecifiers... slices);

类模板 std::default_accessor

namespace std {template<class ElementType>struct default_accessor {using offset_policy = default_accessor;using element_type = ElementType;using reference = ElementType&;using data_handle_type = ElementType*;   constexpr default_accessor()noexcept=default;template<class OtherElementType>constexpr default_accessor(default_accessor<OtherElementType>)noexcept;constexpr reference access(data_handle_type p, size_t i)constnoexcept;constexpr data_handle_type offset(data_handle_type p, size_t i)constnoexcept;};}

类模板 std::strided_slice

namespace std {template<class OffsetType, class ExtentType, class StrideType>struct strided_slice {using offset_type = OffsetType;using extent_type = ExtentType;using stride_type = StrideType;   [[no_unique_address]] offset_type offset{};[[no_unique_address]] extent_type extent{};[[no_unique_address]] stride_type stride{};};}

类模板 std::submdspan_mapping_result

namespace std {template<class LayoutMapping>struct submdspan_mapping_result {[[no_unique_address]] LayoutMapping mapping = LayoutMapping(); size_t offset{};};}

参考

• C++23 标准（ISO/IEC 14882:2024）：

• 24.7.4 Header <mdspan> synopsis [mdspan.syn]