std::extents, std::dextents
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Defined in header
<mdspan> |
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template< class IndexType, std::size_t... Extents >
class extents; |
(1) | (since C++23) |
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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-extentsof 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) |
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Observers |
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[static]
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returns the static rank of an extents(public static member function) |
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[static]
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returns the dynamic rank of an extents(public static member function) |
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[static]
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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) |
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Public exposition-only helpers |
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returns the product of extent size in range [0, i)(exposition-only member function*) |
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returns the product of extents size in range [i + 1, rank())(exposition-only member function*) |
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| casts the input into an integer type (exposition-only member function*) |
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Private exposition-only helpers |
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| returns the number of dynamic extents below a certain rank index (exposition-only member function*) |
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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*) |
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Non-member functions
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(C++23)
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compare underlying extents in each dimension of two extents(function) |
Deduction guides(C++23)
Example
| This section is incomplete Reason: no example |
See also
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(C++11)
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obtains the number of dimensions of an array type (class template) |
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(C++11)
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obtains the size of an array type along a specified dimension (class template) |