std::extents, std::dextents, std::dims - cppreference.com (original) (raw)

Defined in header
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)
template< std::size_t Rank, class IndexType = std::size_t > using dims = std::dextents<IndexType, Rank>; (3) (since C++26)

  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).

  3. A convenient alias template for an all-dynamic extents with std::size_t as the default index type.

Each specialization of extents models regular and is TriviallyCopyable.

Contents

[edit] 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

[edit] Member types

[edit] Data members

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

[edit] Member functions

(constructor) constructs an extents (public member function) [edit]
Observers
rank[static] returns the static rank of an extents (public static member function) [edit]
rank_dynamic[static] returns the dynamic rank of an extents (public static member function) [edit]
static_extent[static] returns static extent size of an extents at a certain rank index (public static member function) [edit]
extent returns dynamic extent size of an extents at a certain rank index (public member function) [edit]
Helpers
fwd-prod-of-extents returns the product of extent size in range [​0​, i)(exposition-only member function*)[edit]
rev-prod-of-extents returns the product of extents size in range [i + 1, rank())(exposition-only member function*)[edit]
index-cast casts the input into an integer type(exposition-only member function*)[edit]
dynamic-index(private) returns the number of dynamic extents below a certain rank index(exposition-only member function*)[edit]
dynamic-index-inv(private) 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*)[edit]

[edit] Non-member functions

| | compare underlying extents in each dimension of two extents (function) [edit] | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

[edit] Deduction guides(C++23)

[edit] Example

[edit] See also

| | obtains the number of dimensions of an array type (class template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | obtains the size of an array type along a specified dimension (class template) [edit] |