All member functions of
span have constant time complexity
.
namespace std {
template<class ElementType, size_t Extent = dynamic_extent>
class span {
public:
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;
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 below) span(const span<OtherElementType, OtherExtent>& s) noexcept;
~span() noexcept = default;
constexpr span& operator=(const span& other) noexcept = default;
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 below> 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;
constexpr size_type size() const noexcept;
constexpr size_type size_bytes() const noexcept;
[[nodiscard]] constexpr bool empty() const noexcept;
constexpr reference operator[](size_type idx) const;
constexpr reference front() const;
constexpr reference back() const;
constexpr pointer data() const noexcept;
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_;
size_type size_;
};
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>>>;
}