std::extents, std::dextents

 

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std::mdspan

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mdspan::mdspan (C++23)

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Observers

mdspan::size (C++23)

mdspan::empty (C++23)

mdspan::stride (C++23)

mdspan::extents (C++23)

mdspan::data_handle (C++23)

mdspan::mapping (C++23)

mdspan::accessor (C++23)

mdspan::is_uniquemdspan::is_exhaustivemdspan::is_stridedmdspan::is_always_uniquemdspan::is_always_exhaustivemdspan::is_always_strided (C++23)(C++23)(C++23)(C++23)(C++23)(C++23)

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swap (C++23)

Helper types and templates

extentsdextents (C++23)(C++23)

layout_right (C++23)

layout_left (C++23)

layout_stride (C++23)

default_accessor (C++23)

Deduction guides(C++23)

 

Defined in header <mdspan>
template< class IndexType, std::size_t... Extents > class extents;	(1)	(since C++23)
template< class IndexType, std::size_t Rank > using dextents = /* see below */	(2)	(since C++23)

1) Represents a multidimensional index space of rank equal to sizeof...(Extents).

2) A convenient alias template for an all-dynamic extents. Let d denote std::dynamic_extent, each specialization of it dextents<TypeIndex, Rank> is equivalent to extents<IndexType, /* d, d, ..., d (d repeats Rank times in total)*/>.

Each specialization of extents models regular and is TriviallyCopyable.

Template parameters

IndexType	-	the type of each non-dynamic Extents. Shall be a signed or unsigned integer type. Otherwise, the program is ill-formed.
Extents	-	represents extent (size of an integer interval) for each rank index. Each element of it is either equal to std::dynamic_extent (in this case, it represents a dynamic extent and the extent size will be determined dynamically), or is representable as a value of type IndexType (then it represents a static extent and the extent size is just the value of it), or else the program is ill-formed.
Rank	-	denotes the rank of an all-dynamic extents.

Member types

Member type	Definition
index_type	IndexType
size_type	std::make_unsigned_t<index_type>
rank_type	std::size_t

Data members

Typical implementations hold only one non-static data member:

• dynamic-extents of type std::array<index_type, rank_dynamic()>, which stores the size of each dynamic extents. The name is for exposition only.

Member functions

(constructor)	constructs an extents (public member function)
Observers
rank [static]	returns the static rank of an extents (public static member function)
rank_dynamic [static]	returns the dynamic rank of an extents (public static member function)
static_extent [static]	returns static extent size of an extents at a certain rank index (public static member function)
extent	returns dynamic extent size of an extents at a certain rank index (public member function)
Public exposition-only helpers
fwd-prod-of-extents	returns the product of extent size in range [​0​, i) (exposition-only member function*)
rev-prod-of-extents	returns the product of extents size in range [i + 1, rank()) (exposition-only member function*)
index-cast	casts the input into an integer type (exposition-only member function*)
Private exposition-only helpers
dynamic-index	returns the number of dynamic extents below a certain rank index (exposition-only member function*)
dynamic-index-inv	returns the number r such that in range [​0​, r + 1) there is exactly i + 1 dynamic extents for a certain argument i (exposition-only member function*)

Non-member functions

operator== (C++23)

compare underlying extents in each dimension of two extents (function)

See also

rank (C++11)	obtains the number of dimensions of an array type (class template)
extent (C++11)	obtains the size of an array type along a specified dimension (class template)