std::extents, std::dextents

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< cpp‎ | container‎ | mdspan
 
 
 
 
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

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

Non-member functions

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

Deduction guides(C++23)

Example

See also

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