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std::mdspan<T,Extents,LayoutPolicy,AccessorPolicy>::mdspan

From cppreference.com
< cpp‎ | container‎ | mdspan
 
 
 
 
constexpr mdspan();
(1) (since C++23)
template< class... OtherIndexTypes >
    constexpr explicit mdspan( data_handle_type p, OtherIndexTypes... exts );
(2) (since C++23)
template< class OtherIndexType, std::size_t N >

    constexpr explicit(N != rank_dynamic())

        mdspan( data_handle_type p, std::span<OtherIndexType, N> exts );
(3) (since C++23)
template< class OtherIndexType, std::size_t N >

    constexpr explicit(N != rank_dynamic())

        mdspan( data_handle_type p, const std::array<OtherIndexType, N>& exts );
(4) (since C++23)
constexpr mdspan( data_handle_type p, const extents_type& ext );
(5) (since C++23)
constexpr mdspan( data_handle_type p, const mapping_type& m );
(6) (since C++23)
constexpr mdspan( data_handle_type p, const mapping_type& m,
                  const accessor_type& a );
(7) (since C++23)
template< class OtherElementType, class OtherExtents,

          class OtherLayoutPolicy, class OtherAccessor >
    constexpr explicit(/* see below */)
        mdspan( const mdspan<OtherElementType, OtherExtents,

                             OtherLayoutPolicy, OtherAccessor>& other );
(8) (since C++23)
constexpr mdspan( const mdspan& rhs ) = default;
(9) (since C++23)
constexpr mdspan( mdspan&& rhs ) = default;
(10) (since C++23)

Construct an mdspan, optionally using user-supplied data handle p, layout mapping m, and accessor a. If extents exts or ext are supplied, they are converted to extents_type and used to initialize the layout mapping.

1) Construct an empty mdspan. Value-initializes ptr_, map_, and acc_.
  • The behavior is undefined if [0map_.required_span_size()) is not an accessible range of ptr_ and acc_ for the values of map_ and acc_ after the invocation of this constructor.
  • This overload participates in overload resolution only if
2) Construct an mdspan over the underlying data referred by p with extents represented by exts.... Value-initializes acc_, direct-non-list-initializes ptr_ with std::move(p) and map_ with extents_type(static_cast<index_type>(std::move(exts))...).
  • The behavior is undefined if [0map_.required_span_size()) is not an accessible range of ptr_ and acc_ for the values of map_ and acc_ after the invocation of this constructor.
  • Let N be sizeof...(OtherIndexTypes). This overload participates in overload resolution only if
3,4) Construct an mdspan over the underlying data referred by p with extents represented by pack exts. Value-initializes acc_, direct-non-list-initializes ptr_ with std::move(p) and map_ with extents_type(exts).
  • The behavior is undefined if [0map_.required_span_size()) is not an accessible range of ptr_ and acc_ for the values of map_ and acc_ after the invocation of this constructor.
  • This overload participates in overload resolution only if
5) Construct an mdspan over the underlying data referred by p with extents represented by ext. Value-initializes acc_, direct-non-list-initializes ptr_ with std::move(p) and map_ with exts.
  • The behavior is undefined if [0map_.required_span_size()) is not an accessible range of p and acc_ for the values of map_ and acc_ after the invocation of this constructor.
  • This overload participates in overload resolution only if
6) Construct an mdspan over the underlying data referred by p with layout mapping m. Value-initializes acc_, direct-non-list-initializes ptr_ with std::move(p) and map_ with m.
  • The behavior is undefined if [0m.required_span_size()) is not an accessible range of p and acc_ for the values of acc_ after the invocation of this constructor.
  • This overload participates in overload resolution only if std::is_default_constructible_v<accessor_type> is true.
7) Construct an mdspan over the underlying data referred by p with layout mapping m and accessor a. Direct-non-list-initializes ptr_ with std::move(p), map_ with m and acc_ with a.
  • The behavior is undefined if [0m.required_span_size()) is not an accessible range of p and a after the invocation of this constructor.
8) Converting constructor from another mdspan. Direct-non-list-initializes ptr_ with other.ptr_, map_ with other.map_ and acc_ with other.acc_.
  • The behavior is undefined if :
  • [0map_.required_span_size()) is not an accessible range of ptr_ and acc_ for the values of map_ and acc_ after the invocation of this constructor, or
  • for each rank index r of extents_type,    extents_type::static_extent(r) == std::dynamic_extent
    || extents_type::static_extent(r) == other.extent(r)
    is false.
  • This overload participates in overload resolution only if
  • The program is ill-formed if:
  • The expression inside explicit is equivalent to:    !std::is_convertible_v<const OtherLayoutPolicy::
           template mapping<OtherExtents>&, mapping_type>
    || !std::is_convertible_v<const OtherAccessor&, accessor_type>

Contents

[edit] Parameters

p - a handle to the underlying data
m - a layout mapping
a - an accessor
ext - a std::extents object
exts - represents a multi-dimensional extents
other - another mdspan to convert from
rhs - another mdspan to copy or move from

[edit] Example

[edit] References

  • C++23 standard (ISO/IEC 14882:2023):
  • 24.7.3.6.2 Constructors [mdspan.mdspan.cons]

[edit] See also