Difference between revisions of "cpp/container/span"
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Revision as of 23:58, 21 June 2020
| Defined in header <span>
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| template< class T, |
(since C++20) | |
The class template span describes an object that can refer to a contiguous sequence of objects with the first element of the sequence at position zero. A span can either have a static extent, in which case the number of elements in the sequence is known and encoded in the type, or a dynamic extent.
A typical implementation holds only two members: a pointer to T and a size.
Contents |
Template parameters
| T | - | element type; must be a complete type that is not an abstract class type |
| Extent | - | the number of elements in the sequence, or std::dynamic_extent if dynamic
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Member types
| Member type | Definition |
element_type
|
T
|
value_type
|
std::remove_cv_t<T> |
size_type
|
std::size_t |
difference_type
|
std::ptrdiff_t |
pointer
|
T*
|
const_pointer
|
const T*
|
reference
|
T&
|
const_reference
|
const T&
|
iterator
|
implementation-defined LegacyRandomAccessIterator, ConstexprIterator, and LegacyContiguousIterator whose value_type is value_type
|
reverse_iterator
|
std::reverse_iterator<iterator> |
Note: iterator is a mutable iterator if T is not const-qualified.
All requirements on the iterator types of a Container apply to the iterator type of span as well.
Member constant
| static constexpr std::size_t extent = Extent; |
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Member functions
constructs a span (public member function) | |
assigns a span (public member function) | |
Iterators | |
| (C++23) |
returns an iterator to the beginning (public member function) |
| (C++23) |
returns an iterator to the end (public member function) |
| (C++23) |
returns a reverse iterator to the beginning (public member function) |
| (C++23) |
returns a reverse iterator to the end (public member function) |
Element access | |
| access the first element (public member function) | |
| access the last element (public member function) | |
Observers | |
| (C++20) |
returns the number of elements in the sequence (public member function) |
| returns the size of the sequence in bytes (public member function) | |
| checks if the sequence is empty (public member function) | |
Subviews | |
obtains a subspan consisting of the first N elements of the sequence (public member function) | |
obtains a subspan consisting of the last N elements of the sequence (public member function) | |
| obtains a subspan (public member function) | |
Non-member functions
| (C++20) |
converts a span into a view of its underlying bytes (function template) |
Non-member constant
| (C++20) |
a constant of type std::size_t signifying that the span has dynamic extent (constant) |
Helper templates
| template<class T, std::size_t Extent> inline constexpr bool ranges::enable_borrowed_range<std::span<T, Extent>> = true; |
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This specialization of std::ranges::enable_borrowed_range makes span satisfy borrowed_range.
| template<class T, std::size_t Extent> inline constexpr bool ranges::enable_view<std::span<T, Extent>> = |
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This specialization of std::ranges::enable_view makes span of zero or dynamic extent satisfy view. Spans of nonzero static extent are not default_initializable and therefore not views.
