NAME¶

std::extents,std::dextents - std::extents,std::dextents

Synopsis¶

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

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<IndexType, Rank> is
equivalent to extents<IndexType /*, d, d, ..., d*/> (i.e. d is repeated a total of
Rank times).

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
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,
Extents - 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

Member objects¶

Member name Definition
An array of type std::array<index_type, rank_dynamic()>,
dynamic-extents (private) which stores the size of each dynamic extents.
(exposition-only member object*)

Member functions¶

constructor constructs an extents
(public member function)

Observers¶

rank returns the static rank of an extents
[static] (public static member function)
rank_dynamic returns the dynamic rank of an extents
[static] (public static member function)
static_extent returns static extent size of an extents at a certain rank index
[static] (public static member function)
returns dynamic extent size of an extents at a certain rank
extent index
(public member function)
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*)
dynamic-index returns the number of dynamic extents below a certain rank index
(private) (exposition-only member function*)
dynamic-index-inv returns the number r such that in range [0, r + 1) there is
(private) exactly i + 1 dynamic extents for a certain argument i
(exposition-only member function*)

Non-member functions¶

operator== compare underlying extents in each dimension of two extents
(C++23) (function)

Deduction guides(C++23)

Example¶

This section is incomplete
Reason: no example

See also¶

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

Category:¶

* Todo no example