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

 

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std::mdspan

Member functions mdspan::mdspan mdspan::operator= Element access mdspan::operator[] Observers mdspan::rank mdspan::rank_dynamic mdspan::static_extent mdspan::extent mdspan::size mdspan::empty mdspan::stride mdspan::extents mdspan::data_handle mdspan::mapping mdspan::accessor mdspan::is_uniquemdspan::is_exhaustivemdspan::is_stridedmdspan::is_always_uniquemdspan::is_always_exhaustivemdspan::is_always_strided

Non-member functions swap(std::mdspan) Subviews submdspan (C++26) submdspan_extents (C++26) Helper types and templates extentsdextents dims (C++26) default_accessor aligned_accessor (C++26) Layout mapping policies layout_left layout_right layout_stride layout_left_padded (C++26) layout_right_padded (C++26) Subviews helpers full_extent (C++26) strided_slice (C++26) submdspan_mapping_result (C++26) Deduction guides

 

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)

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.

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

Effects

For the data members listed in the table below:

• If the corresponding initializer is empty, the data member is value-initialized.
• If the corresponding intiializer is not empty, the data member is direct-non-list-initialized with that initializer.

Overload	Initializer for...
	ptr_	map_	acc_
(1)	(empty)
(2)	std::move(p)	extents_type (static_cast<index_type> (std::move(exts))...)	(empty)
(3)		extents_type(exts)
(4)
(5)		ext
(6)		m
(7)			a
(8)	other.ptr_	other.map_	other.acc_

Constraints and supplement information

1) This overload participates in overload resolution only if all following values are true:

• rank_dynamic() > 0
• std::is_default_constructible_v<data_handle_type>
• std::is_default_constructible_v<mapping_type>
• std::is_default_constructible_v<accessor_type>

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, the behavior is undefined.

2) This overload participates in overload resolution only if all following values are true:

• (std::is_convertible_v<OtherIndexTypes, index_type> && ...)
• (std::is_nothrow_constructible<index_type, OtherIndexTypes> && ...)
• sizeof...(OtherIndexTypes) == rank() || sizeof...(OtherIndexTypes) == rank_dynamic()
• std::is_constructible_v<mapping_type, extents_type>
• std::is_default_constructible_v<accessor_type>

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 these constructors, the behavior is undefined.

3,4) These overloads participate in overload resolution only if all following values are true:

• std::is_convertible_v<const OtherIndexType&, index_type>
• std::is_nothrow_constructible_v<index_type, const OtherIndexType&>
• N == rank() || N == rank_dynamic()
• std::is_constructible_v<mapping_type, extents_type>
• std::is_default_constructible_v<accessor_type>

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 these constructors, the behavior is undefined.

5) This overload participates in overload resolution only if all following values are true:

• std::is_constructible_v<mapping_type, const extents_type&>
• std::is_default_constructible_v<accessor_type>

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 these constructors, the behavior is undefined.

6) This overload participates in overload resolution only if std::is_default_constructible_v<accessor_type> is true.

If [0, m.required_span_size()) is an accessible range of p and acc_ for the value of acc_ after the invocation of this constructor, the behavior is undefined.

7) If [0, m.required_span_size()) is not an accessible range of p and a, the behavior is undefined.

8) 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>.

This overload participates in overload resolution only if all following values are true:

• std::is_constructible_v
<mapping_type, const OtherLayoutPolicy::template mapping<OtherExtents>&>
• std::is_default_constructible_v<accessor_type>

If any of the following values is false, the program is ill-formed:

• std::is_constructible_v<data_handle_type, const OtherAccessor::data_handle_type&>
• std::is_constructible_v<extents_type, OtherExtents>

If [0, map_ .required_span_size()) is not an accessible range of ptr_ and acc_ for the values of ptr_, map_ and acc_ after the invocation of this constructor, the behavior is undefined.

If static_extent(r) == std::dynamic_extent || static_extent(r) == other.extent(r) is false for some rank index r of extents_type, the behavior is undefined.	(until C++26)
If static_extent(r) == std::dynamic_extent || static_extent(r) == other.extent(r) is false for some rank index r of extents_type: If the implementation is hardened, a contract violation occurs. If the implementation is not hardened, the behavior is undefined.	(since C++26)

Example

References

• C++23 standard (ISO/IEC 14882:2024):

• 24.7.3.6.2 Constructors [mdspan.mdspan.cons]

See also