NAME¶

std::mdspan::mdspan - std::mdspan::mdspan

Synopsis¶

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

constexpr explicit(N != rank_dynamic()) (3) (since C++23)

mdspan( data_handle_type p, std::span<OtherIndexType, N>
exts );
template< class OtherIndexType, std::size_t N >

constexpr explicit(N != rank_dynamic()) (4) (since C++23)

mdspan( data_handle_type p, const
std::array<OtherIndexType, N>& exts );
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, (7) (since C++23)
const accessor_type& a );
template< class OtherElementType, class OtherExtents,

class OtherLayoutPolicy, class OtherAccessor >
constexpr explicit(/* see below */) (8) (since C++23)
mdspan( const mdspan<OtherElementType, OtherExtents,

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

Constructs 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) Constructs an empty mdspan. Value-initializes ptr_, map_, and acc_.
* The behavior is undefined if [0, map_.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

* rank_dynamic() > 0 is true,
* std::is_default_constructible_v<data_handle_type> is true,
* std::is_default_constructible_v<mapping_type> is true, and
* std::is_default_constructible_v<accessor_type> is true.
2) Constructs 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 [0, map_.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

* (std::is_convertible_v<OtherIndexTypes, index_type> && ...) is true,
* (std::is_nothrow_constructible<index_type, OtherIndexTypes> && ...) is true,
* N == rank() || N == rank_dynamic() is true,
* std::is_constructible_v<mapping_type, extents_type> is true, and
* std::is_default_constructible_v<accessor_type> is true.
3,4) Constructs 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 [0, map_.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

* std::is_convertible_v<const OtherIndexTypes&, index_type> is true,
* std::is_nothrow_constructible<index_type, const OtherIndexTypes&> is true,
* N == rank() || N == rank_dynamic() is true,
* std::is_constructible_v<mapping_type, extents_type> is true, and
* std::is_default_constructible_v<accessor_type> is true.
5) Constructs 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 [0, map_.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

* std::is_constructible_v<mapping_type, const mapping_type&> is true, and
* std::is_default_constructible_v<accessor_type> is true.
6) Constructs 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 [0, m.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) Constructs 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 [0, m.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 :

* [0, map_.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

* std::is_constructible_v<mapping_type, const OtherLayoutPolicy::
template mapping<OtherExtents>&> is true, and
* std::is_constructible_v<accessor_type, const OtherAccessor&> is true.
* The program is ill-formed if:

* std::is_constructible_v<data_handle_type,
const OtherAccessor::data_handle_type&> is false, or
* std::is_constructible_v<extents_type, OtherExtents> is false.
* 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>
9) Defaulted copy constructor.
10) Defaulted move constructor.

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

Example¶

This section is incomplete
Reason: no example

References¶

* C++23 standard (ISO/IEC 14882:2023):

* 24.7.3.6.2 Constructors [mdspan.mdspan.cons]

See also¶

This section is incomplete

Categories:¶

* Todo no example
* Todo without reason