Standard library header <span>
This header is part of the container library.
Classes |
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(C++20)
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a non-owning view over a contiguous sequence of objects (class template) |
Constants |
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(C++20)
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a constant of type size_t signifying that the span has dynamic extent (constant) |
Functions |
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(C++20)
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converts a span into a view of its underlying bytes (function template) |
Range access |
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(C++11)(C++14)
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returns an iterator to the beginning of a container or array (function template) |
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(C++11)(C++14)
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returns an iterator to the end of a container or array (function template) |
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(C++14)
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returns a reverse iterator to the beginning of a container or array (function template) |
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(C++14)
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returns a reverse end iterator for a container or array (function template) |
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(C++17)(C++20)
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returns the size of a container or array (function template) |
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(C++17)
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checks whether the container is empty (function template) |
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(C++17)
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obtains the pointer to the underlying array (function template) |
Synopsis
namespace std {
// constants
inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
// class template span
template<class ElementType, size_t Extent = dynamic_extent>
class span;
template<class ElementType, size_t Extent>
inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
// views of object representation
template<class ElementType, size_t Extent>
span<const byte,
Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
as_bytes(span<ElementType, Extent> s) noexcept;
template<class ElementType, size_t Extent>
span<byte, Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
as_writable_bytes(span<ElementType, Extent> s) noexcept;
}
Class template std::span
namespace std {
template<class ElementType, size_t Extent = dynamic_extent>
class span {
public:
// constants and types
using element_type = ElementType;
using value_type = remove_cv_t<ElementType>;
using size_type = size_t;
using difference_type = ptrdiff_t;
using pointer = element_type*;
using const_pointer = const element_type*;
using reference = element_type&;
using const_reference = const element_type&;
using iterator = /* implementation-defined */;
using reverse_iterator = std::reverse_iterator<iterator>;
static constexpr size_type extent = Extent;
// constructors, copy, and assignment
constexpr span() noexcept;
template<class It>
constexpr explicit(extent != dynamic_extent) span(It first, size_type count);
template<class It, class End>
constexpr explicit(extent != dynamic_extent) span(It first, End last);
template<size_t N>
constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
template<class T, size_t N>
constexpr span(array<T, N>& arr) noexcept;
template<class T, size_t N>
constexpr span(const array<T, N>& arr) noexcept;
template<class R>
constexpr explicit(extent != dynamic_extent) span(R&& r);
constexpr span(const span& other) noexcept = default;
template<class OtherElementType, size_t OtherExtent>
constexpr explicit(/* see description */)
span(const span<OtherElementType, OtherExtent>& s) noexcept;
~span() noexcept = default;
constexpr span& operator=(const span& other) noexcept = default;
// subviews
template<size_t Count>
constexpr span<element_type, Count> first() const;
template<size_t Count>
constexpr span<element_type, Count> last() const;
template<size_t Offset, size_t Count = dynamic_extent>
constexpr span<element_type, /* see description */> subspan() const;
constexpr span<element_type, dynamic_extent> first(size_type count) const;
constexpr span<element_type, dynamic_extent> last(size_type count) const;
constexpr span<element_type, dynamic_extent> subspan(
size_type offset, size_type count = dynamic_extent) const;
// observers
constexpr size_type size() const noexcept;
constexpr size_type size_bytes() const noexcept;
[[nodiscard]] constexpr bool empty() const noexcept;
// element access
constexpr reference operator[](size_type idx) const;
constexpr reference front() const;
constexpr reference back() const;
constexpr pointer data() const noexcept;
// iterator support
constexpr iterator begin() const noexcept;
constexpr iterator end() const noexcept;
constexpr reverse_iterator rbegin() const noexcept;
constexpr reverse_iterator rend() const noexcept;
private:
pointer data_; // exposition only
size_type size_; // exposition only
};
template<class It, class EndOrSize>
span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<It>>>;
template<class T, size_t N>
span(T (&)[N]) -> span<T, N>;
template<class T, size_t N>
span(array<T, N>&) -> span<T, N>;
template<class T, size_t N>
span(const array<T, N>&) -> span<const T, N>;
template<class R>
span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
}
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