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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===---------------------------------------------------------------------===//
#ifndef _LIBCPP_SPAN
#define _LIBCPP_SPAN
/*
span synopsis
namespace std {
// constants
inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
// [views.span], class template span
template <class ElementType, size_t Extent = dynamic_extent>
class span;
template<class ElementType, size_t Extent>
inline constexpr bool ranges::enable_view<span<ElementType, Extent>> = true;
template<class ElementType, size_t Extent>
inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
// [span.objectrep], 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;
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;
// [span.cons], span constructors, copy, assignment, and destructor
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 <size_t N>
constexpr span(array<value_type, N>& arr) noexcept;
template <size_t N>
constexpr span(const array<value_type, 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(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept;
~span() noexcept = default;
constexpr span& operator=(const span& other) noexcept = default;
// [span.sub], span 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 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;
// [span.obs], span observers
constexpr size_type size() const noexcept;
constexpr size_type size_bytes() const noexcept;
[[nodiscard]] constexpr bool empty() const noexcept;
// [span.elem], span element access
constexpr reference operator[](size_type idx) const;
constexpr reference front() const;
constexpr reference back() const;
constexpr pointer data() const noexcept;
// [span.iterators], span 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>>>;
} // namespace std
*/
#include <__assert> // all public C++ headers provide the assertion handler
#include <__config>
#include <__debug>
#include <__fwd/span.h>
#include <__iterator/concepts.h>
#include <__iterator/wrap_iter.h>
#include <__ranges/concepts.h>
#include <__ranges/data.h>
#include <__ranges/enable_borrowed_range.h>
#include <__ranges/enable_view.h>
#include <__ranges/size.h>
#include <__utility/forward.h>
#include <array> // for array
#include <cstddef> // for byte
#include <iterator> // for iterators
#include <limits>
#include <type_traits> // for remove_cv, etc
#include <version>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
template <class _Tp>
struct __is_std_array : false_type {};
template <class _Tp, size_t _Sz>
struct __is_std_array<array<_Tp, _Sz>> : true_type {};
template <class _Tp>
struct __is_std_span : false_type {};
template <class _Tp, size_t _Sz>
struct __is_std_span<span<_Tp, _Sz>> : true_type {};
#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
// This is a temporary workaround until we ship <ranges> -- we've unfortunately been
// shipping <span> before its API was finalized, and we used to provide a constructor
// from container types that had the requirements below. To avoid breaking code that
// has started relying on the range-based constructor until we ship all of <ranges>,
// we emulate the constructor requirements like this.
template <class _Range, class _ElementType>
concept __span_compatible_range =
!__is_std_span<remove_cvref_t<_Range>>::value &&
!__is_std_array<remove_cvref_t<_Range>>::value &&
!is_array_v<remove_cvref_t<_Range>> &&
requires (_Range&& __r) {
data(std::forward<_Range>(__r));
size(std::forward<_Range>(__r));
} &&
is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>;
#else
template <class _Range, class _ElementType>
concept __span_compatible_range =
ranges::contiguous_range<_Range> &&
ranges::sized_range<_Range> &&
(ranges::borrowed_range<_Range> || is_const_v<_ElementType>) &&
!__is_std_span<remove_cvref_t<_Range>>::value &&
!__is_std_array<remove_cvref_t<_Range>>::value &&
!is_array_v<remove_cvref_t<_Range>> &&
is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>;
#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
template <typename _Tp, size_t _Extent>
class _LIBCPP_TEMPLATE_VIS span {
public:
// constants and types
using element_type = _Tp;
using value_type = remove_cv_t<_Tp>;
using size_type = size_t;
using difference_type = ptrdiff_t;
using pointer = _Tp *;
using const_pointer = const _Tp *;
using reference = _Tp &;
using const_reference = const _Tp &;
#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS)
using iterator = pointer;
#else
using iterator = __wrap_iter<pointer>;
#endif
using reverse_iterator = _VSTD::reverse_iterator<iterator>;
static constexpr size_type extent = _Extent;
// [span.cons], span constructors, copy, assignment, and destructor
template <size_t _Sz = _Extent, enable_if_t<_Sz == 0, nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr} {}
constexpr span (const span&) noexcept = default;
constexpr span& operator=(const span&) noexcept = default;
template <class _It,
enable_if_t<contiguous_iterator<_It> &&
is_convertible_v<remove_reference_t<iter_reference_t<_It>>(*)[], element_type (*)[]>,
nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(_It __first, size_type __count)
: __data{_VSTD::to_address(__first)} {
(void)__count;
_LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
}
template <
class _It, class _End,
enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> &&
contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>,
nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(_It __first, _End __last) : __data{_VSTD::to_address(__first)} {
(void)__last;
_LIBCPP_ASSERT((__last - __first >= 0), "invalid range in span's constructor (iterator, sentinel)");
_LIBCPP_ASSERT(__last - __first == _Extent,
"invalid range in span's constructor (iterator, sentinel): last - first != extent");
}
_LIBCPP_INLINE_VISIBILITY constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data{__arr} {}
template <class _OtherElementType,
enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {}
template <class _OtherElementType,
enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {}
#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
template <class _Container>
requires __span_compatible_range<_Container, element_type>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(_Container& __c) : __data{std::data(__c)} {
_LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)");
}
template <class _Container>
requires __span_compatible_range<const _Container, element_type>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(const _Container& __c) : __data{std::data(__c)} {
_LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)");
}
#else
template <__span_compatible_range<element_type> _Range>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(_Range&& __r) : __data{ranges::data(__r)} {
_LIBCPP_ASSERT(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)");
}
#endif
template <class _OtherElementType>
_LIBCPP_INLINE_VISIBILITY
constexpr span(const span<_OtherElementType, _Extent>& __other,
enable_if_t<
is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
nullptr_t> = nullptr)
: __data{__other.data()} {}
template <class _OtherElementType>
_LIBCPP_INLINE_VISIBILITY
constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other,
enable_if_t<
is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
nullptr_t> = nullptr) noexcept
: __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); }
// ~span() noexcept = default;
template <size_t _Count>
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> first() const noexcept
{
static_assert(_Count <= _Extent, "Count out of range in span::first()");
return span<element_type, _Count>{data(), _Count};
}
template <size_t _Count>
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> last() const noexcept
{
static_assert(_Count <= _Extent, "Count out of range in span::last()");
return span<element_type, _Count>{data() + size() - _Count, _Count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
{
_LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
return {data(), __count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept
{
_LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
return {data() + size() - __count, __count};
}
template <size_t _Offset, size_t _Count = dynamic_extent>
_LIBCPP_INLINE_VISIBILITY
constexpr auto subspan() const noexcept
-> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>
{
static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()");
static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, "Offset + count out of range in span::subspan()");
using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent>
subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
{
_LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
_LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)");
if (__count == dynamic_extent)
return {data() + __offset, size() - __offset};
_LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)");
return {data() + __offset, __count};
}
_LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; }
_LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
[[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; }
_LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx < size(), "span<T,N>[] index out of bounds");
return __data[__idx];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
{
_LIBCPP_ASSERT(!empty(), "span<T, N>::front() on empty span");
return __data[0];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
{
_LIBCPP_ASSERT(!empty(), "span<T, N>::back() on empty span");
return __data[size()-1];
}
_LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
// [span.iter], span iterator support
_LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
_LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
_LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
_LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
_LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept
{ return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte *>(data()), size_bytes()}; }
_LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept
{ return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte *>(data()), size_bytes()}; }
private:
pointer __data;
};
template <typename _Tp>
class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
private:
public:
// constants and types
using element_type = _Tp;
using value_type = remove_cv_t<_Tp>;
using size_type = size_t;
using difference_type = ptrdiff_t;
using pointer = _Tp *;
using const_pointer = const _Tp *;
using reference = _Tp &;
using const_reference = const _Tp &;
#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS)
using iterator = pointer;
#else
using iterator = __wrap_iter<pointer>;
#endif
using reverse_iterator = _VSTD::reverse_iterator<iterator>;
static constexpr size_type extent = dynamic_extent;
// [span.cons], span constructors, copy, assignment, and destructor
_LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {}
constexpr span (const span&) noexcept = default;
constexpr span& operator=(const span&) noexcept = default;
template <class _It,
enable_if_t<contiguous_iterator<_It> &&
is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]>,
nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(_It __first, size_type __count)
: __data{_VSTD::to_address(__first)}, __size{__count} {}
template <
class _It, class _End,
enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> &&
contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>,
nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(_It __first, _End __last)
: __data(_VSTD::to_address(__first)), __size(__last - __first) {}
template <size_t _Sz>
_LIBCPP_INLINE_VISIBILITY
constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {}
template <class _OtherElementType, size_t _Sz,
enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
template <class _OtherElementType, size_t _Sz,
enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
_LIBCPP_INLINE_VISIBILITY
constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
template <class _Container>
requires __span_compatible_range<_Container, element_type>
_LIBCPP_INLINE_VISIBILITY
constexpr span(_Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {}
template <class _Container>
requires __span_compatible_range<const _Container, element_type>
_LIBCPP_INLINE_VISIBILITY
constexpr span(const _Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {}
#else
template <__span_compatible_range<element_type> _Range>
_LIBCPP_INLINE_VISIBILITY
constexpr span(_Range&& __r) : __data(ranges::data(__r)), __size{ranges::size(__r)} {}
#endif
template <class _OtherElementType, size_t _OtherExtent>
_LIBCPP_INLINE_VISIBILITY
constexpr span(const span<_OtherElementType, _OtherExtent>& __other,
enable_if_t<
is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
nullptr_t> = nullptr) noexcept
: __data{__other.data()}, __size{__other.size()} {}
// ~span() noexcept = default;
template <size_t _Count>
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> first() const noexcept
{
_LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()");
return span<element_type, _Count>{data(), _Count};
}
template <size_t _Count>
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> last() const noexcept
{
_LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()");
return span<element_type, _Count>{data() + size() - _Count, _Count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
{
_LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
return {data(), __count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept
{
_LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
return {data() + size() - __count, __count};
}
template <size_t _Offset, size_t _Count = dynamic_extent>
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> subspan() const noexcept
{
_LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()");
_LIBCPP_ASSERT(_Count == dynamic_extent || _Count <= size() - _Offset, "Offset + count out of range in span::subspan()");
return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
}
constexpr span<element_type, dynamic_extent>
_LIBCPP_INLINE_VISIBILITY
subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
{
_LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
_LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)");
if (__count == dynamic_extent)
return {data() + __offset, size() - __offset};
_LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)");
return {data() + __offset, __count};
}
_LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; }
_LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); }
[[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; }
_LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx < size(), "span<T>[] index out of bounds");
return __data[__idx];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
{
_LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span");
return __data[0];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
{
_LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span");
return __data[size()-1];
}
_LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
// [span.iter], span iterator support
_LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
_LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
_LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
_LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
_LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept
{ return {reinterpret_cast<const byte *>(data()), size_bytes()}; }
_LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept
{ return {reinterpret_cast<byte *>(data()), size_bytes()}; }
private:
pointer __data;
size_type __size;
};
template <class _Tp, size_t _Extent>
inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true;
template <class _ElementType, size_t _Extent>
inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true;
// as_bytes & as_writable_bytes
template <class _Tp, size_t _Extent>
_LIBCPP_INLINE_VISIBILITY
auto as_bytes(span<_Tp, _Extent> __s) noexcept
-> decltype(__s.__as_bytes())
{ return __s.__as_bytes(); }
template <class _Tp, size_t _Extent>
_LIBCPP_INLINE_VISIBILITY
auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept
-> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())>
{ return __s.__as_writable_bytes(); }
#if _LIBCPP_STD_VER > 17
template<contiguous_iterator _It, class _EndOrSize>
span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
#endif // _LIBCPP_STD_VER > 17
template<class _Tp, size_t _Sz>
span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
template<class _Tp, size_t _Sz>
span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
template<class _Tp, size_t _Sz>
span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
template<class _Container>
span(_Container&) -> span<typename _Container::value_type>;
template<class _Container>
span(const _Container&) -> span<const typename _Container::value_type>;
#else
template<ranges::contiguous_range _Range>
span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>;
#endif
#endif // _LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP_SPAN
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