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|
// -*- C++ -*-
//===------------------------------ span ---------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//
#ifndef _LIBCPP_SPAN
#define _LIBCPP_SPAN
/*
span synopsis
namespace std {
// constants
inline constexpr ptrdiff_t dynamic_extent = -1;
// [views.span], class template span
template <class ElementType, ptrdiff_t Extent = dynamic_extent>
class span;
// [span.comparison], span comparison operators
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator==(span<T, X> l, span<U, Y> r);
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator!=(span<T, X> l, span<U, Y> r);
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator<(span<T, X> l, span<U, Y> r);
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator<=(span<T, X> l, span<U, Y> r);
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator>(span<T, X> l, span<U, Y> r);
template <class T, ptrdiff_t X, class U, ptrdiff_t Y>
constexpr bool operator>=(span<T, X> l, span<U, Y> r);
// [span.objectrep], views of object representation
template <class ElementType, ptrdiff_t Extent>
span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
(static_cast<ptrdiff_t>(sizeof(ElementType)) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
template <class ElementType, ptrdiff_t Extent>
span< byte, ((Extent == dynamic_extent) ? dynamic_extent :
(static_cast<ptrdiff_t>(sizeof(ElementType)) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
namespace std {
template <class ElementType, ptrdiff_t Extent = dynamic_extent>
class span {
public:
// constants and types
using element_type = ElementType;
using value_type = remove_cv_t<ElementType>;
using index_type = ptrdiff_t;
using difference_type = ptrdiff_t;
using pointer = element_type*;
using reference = element_type&;
using iterator = implementation-defined;
using const_iterator = implementation-defined;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
static constexpr index_type extent = Extent;
// [span.cons], span constructors, copy, assignment, and destructor
constexpr span() noexcept;
constexpr span(pointer ptr, index_type count);
constexpr span(pointer firstElem, pointer lastElem);
template <size_t N>
constexpr span(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 Container>
constexpr span(Container& cont);
template <class Container>
constexpr span(const Container& cont);
constexpr span(const span& other) noexcept = default;
template <class OtherElementType, ptrdiff_t OtherExtent>
constexpr span(const span<OtherElementType, OtherExtent>& s) noexcept;
~span() noexcept = default;
constexpr span& operator=(const span& other) noexcept = default;
// [span.sub], span subviews
template <ptrdiff_t Count>
constexpr span<element_type, Count> first() const;
template <ptrdiff_t Count>
constexpr span<element_type, Count> last() const;
template <ptrdiff_t Offset, ptrdiff_t Count = dynamic_extent>
constexpr span<element_type, see below> subspan() const;
constexpr span<element_type, dynamic_extent> first(index_type count) const;
constexpr span<element_type, dynamic_extent> last(index_type count) const;
constexpr span<element_type, dynamic_extent> subspan(index_type offset, index_type count = dynamic_extent) const;
// [span.obs], span observers
constexpr index_type size() const noexcept;
constexpr index_type size_bytes() const noexcept;
constexpr bool empty() const noexcept;
// [span.elem], span element access
constexpr reference operator[](index_type idx) const;
constexpr reference operator()(index_type idx) const;
constexpr pointer data() const noexcept;
// [span.iterators], span iterator support
constexpr iterator begin() const noexcept;
constexpr iterator end() const noexcept;
constexpr const_iterator cbegin() const noexcept;
constexpr const_iterator cend() const noexcept;
constexpr reverse_iterator rbegin() const noexcept;
constexpr reverse_iterator rend() const noexcept;
constexpr const_reverse_iterator crbegin() const noexcept;
constexpr const_reverse_iterator crend() const noexcept;
private:
pointer data_; // exposition only
index_type size_; // exposition only
};
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 Container>
span(Container&) -> span<typename Container::value_type>;
template<class Container>
span(const Container&) -> span<const typename Container::value_type>;
} // namespace std
*/
#include <__config>
#include <cstddef> // for ptrdiff_t
#include <iterator> // for iterators
#include <array> // for array
#include <type_traits> // for remove_cv, etc
#include <cstddef> // for byte
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
inline constexpr ptrdiff_t dynamic_extent = -1;
template <typename _Tp, ptrdiff_t _Extent = dynamic_extent> class span;
template <class _Tp>
struct __is_span_impl : public false_type {};
template <class _Tp, ptrdiff_t _Extent>
struct __is_span_impl<span<_Tp, _Extent>> : public true_type {};
template <class _Tp>
struct __is_span : public __is_span_impl<remove_cv_t<_Tp>> {};
template <class _Tp>
struct __is_std_array_impl : public false_type {};
template <class _Tp, size_t _Sz>
struct __is_std_array_impl<array<_Tp, _Sz>> : public true_type {};
template <class _Tp>
struct __is_std_array : public __is_std_array_impl<remove_cv_t<_Tp>> {};
template <class _Tp, class _ElementType, class = void>
struct __is_span_compatible_container : public false_type {};
template <class _Tp, class _ElementType>
struct __is_span_compatible_container<_Tp, _ElementType,
void_t<
// is not a specialization of span
typename enable_if<!__is_span<_Tp>::value, nullptr_t>::type,
// is not a specialization of array
typename enable_if<!__is_std_array<_Tp>::value, nullptr_t>::type,
// is_array_v<Container> is false,
typename enable_if<!is_array_v<_Tp>, nullptr_t>::type,
// data(cont) and size(cont) are well formed
decltype(data(declval<_Tp>())),
decltype(size(declval<_Tp>())),
// remove_pointer_t<decltype(data(cont))>(*)[] is convertible to ElementType(*)[]
typename enable_if<
is_convertible_v<remove_pointer_t<decltype(data(declval<_Tp &>()))>(*)[],
_ElementType(*)[]>,
nullptr_t>::type
>>
: public true_type {};
template <typename _Tp, ptrdiff_t _Extent>
class _LIBCPP_TEMPLATE_VIS span {
public:
// constants and types
using element_type = _Tp;
using value_type = remove_cv_t<_Tp>;
using index_type = ptrdiff_t;
using difference_type = ptrdiff_t;
using pointer = _Tp *;
using const_pointer = const _Tp *; // not in standard
using reference = _Tp &;
using const_reference = const _Tp &; // not in standard
using iterator = __wrap_iter<pointer>;
using const_iterator = __wrap_iter<const_pointer>;
using reverse_iterator = _VSTD::reverse_iterator<iterator>;
using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
static constexpr index_type extent = _Extent;
static_assert (_Extent >= 0, "Can't have a span with an extent < 0");
// [span.cons], span constructors, copy, assignment, and destructor
_LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}
{ static_assert(_Extent == 0, "Can't default construct a statically sized span with size > 0"); }
constexpr span (const span&) noexcept = default;
constexpr span& operator=(const span&) noexcept = default;
_LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, index_type __count) : __data{__ptr}
{ (void)__count; _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (ptr, len)"); }
_LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}
{ (void)__l; _LIBCPP_ASSERT(_Extent == distance(__f, __l), "size mismatch in span's constructor (ptr, ptr)"); }
_LIBCPP_INLINE_VISIBILITY constexpr span(element_type (&__arr)[_Extent]) noexcept : __data{__arr} {}
_LIBCPP_INLINE_VISIBILITY constexpr span( array<value_type, _Extent>& __arr) noexcept : __data{__arr.data()} {}
_LIBCPP_INLINE_VISIBILITY constexpr span(const array<value_type, _Extent>& __arr) noexcept : __data{__arr.data()} {}
template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span( _Container& __c,
enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
: __data{_VSTD::data(__c)}
{ _LIBCPP_ASSERT(_Extent == _VSTD::size(__c), "size mismatch in span's constructor (container))"); }
template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span(const _Container& __c,
enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
: __data{_VSTD::data(__c)}
{ _LIBCPP_ASSERT(_Extent == _VSTD::size(__c), "size mismatch in span's constructor (const container)"); }
template <class _OtherElementType>
inline _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>
inline _LIBCPP_INLINE_VISIBILITY
constexpr 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 <ptrdiff_t _Count>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> first() const noexcept
{
static_assert(_Count >= 0, "Count must be >= 0 in span::first()");
static_assert(_Count <= _Extent, "Count out of range in span::first()");
return {data(), _Count};
}
template <ptrdiff_t _Count>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> last() const noexcept
{
static_assert(_Count >= 0, "Count must be >= 0 in span::last()");
static_assert(_Count <= _Extent, "Count out of range in span::last()");
return {data() + size() - _Count, _Count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> first(index_type __count) const noexcept
{
_LIBCPP_ASSERT(__count >= 0 && __count <= size(), "Count out of range in span::first(count)");
return {data(), __count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> last(index_type __count) const noexcept
{
_LIBCPP_ASSERT(__count >= 0 && __count <= size(), "Count out of range in span::last(count)");
return {data() + size() - __count, __count};
}
template <ptrdiff_t _Offset, ptrdiff_t _Count = dynamic_extent>
inline _LIBCPP_INLINE_VISIBILITY
constexpr auto subspan() const noexcept
-> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>
{
_LIBCPP_ASSERT(_Offset >= 0 && _Offset <= size(), "Offset out of range in span::subspan()");
return {data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
}
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent>
subspan(index_type __offset, index_type __count = dynamic_extent) const noexcept
{
_LIBCPP_ASSERT( __offset >= 0 && __offset <= size(), "Offset out of range in span::subspan(offset, count)");
_LIBCPP_ASSERT((__count >= 0 && __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(__offset + __count <= size(), "count + offset out of range in span::subspan(offset, count)");
return {data() + __offset, __count};
}
_LIBCPP_INLINE_VISIBILITY constexpr index_type size() const noexcept { return _Extent; }
_LIBCPP_INLINE_VISIBILITY constexpr index_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
_LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; }
_LIBCPP_INLINE_VISIBILITY constexpr reference operator[](index_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T,N>[] index out of bounds");
return __data[__idx];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference operator()(index_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T,N>() index out of bounds");
return __data[__idx];
}
_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 const_iterator cbegin() const noexcept { return const_iterator(data()); }
_LIBCPP_INLINE_VISIBILITY constexpr const_iterator cend() const noexcept { return const_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 constexpr const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(cend()); }
_LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crend() const noexcept { return const_reverse_iterator(cbegin()); }
_LIBCPP_INLINE_VISIBILITY constexpr void swap(span &__other) noexcept
{
pointer __p = __data;
__data = __other.__data;
__other.__data = __p;
}
_LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept
{ return {reinterpret_cast<const byte *>(data()), size_bytes()}; }
_LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writeable_bytes() const noexcept
{ return {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 index_type = ptrdiff_t;
using difference_type = ptrdiff_t;
using pointer = _Tp *;
using const_pointer = const _Tp *; // not in standard
using reference = _Tp &;
using const_reference = const _Tp &; // not in standard
using iterator = __wrap_iter<pointer>;
using const_iterator = __wrap_iter<const_pointer>;
using reverse_iterator = _VSTD::reverse_iterator<iterator>;
using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
static constexpr index_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;
_LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, index_type __count) : __data{__ptr}, __size{__count} {}
_LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}, __size{distance(__f, __l)} {}
template <size_t _Sz>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span(element_type (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {}
template <size_t _Sz>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span(array<value_type, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
template <size_t _Sz>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span(const array<value_type, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span( _Container& __c,
enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
: __data{_VSTD::data(__c)}, __size{(index_type) _VSTD::size(__c)} {}
template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span(const _Container& __c,
enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
: __data{_VSTD::data(__c)}, __size{(index_type) _VSTD::size(__c)} {}
template <class _OtherElementType, ptrdiff_t _OtherExtent>
inline _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 <ptrdiff_t _Count>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> first() const noexcept
{
static_assert(_Count >= 0);
_LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()");
return {data(), _Count};
}
template <ptrdiff_t _Count>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, _Count> last() const noexcept
{
static_assert(_Count >= 0);
_LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()");
return {data() + size() - _Count, _Count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> first(index_type __count) const noexcept
{
_LIBCPP_ASSERT(__count >= 0 && __count <= size(), "Count out of range in span::first(count)");
return {data(), __count};
}
_LIBCPP_INLINE_VISIBILITY
constexpr span<element_type, dynamic_extent> last (index_type __count) const noexcept
{
_LIBCPP_ASSERT(__count >= 0 && __count <= size(), "Count out of range in span::last(count)");
return {data() + size() - __count, __count};
}
template <ptrdiff_t _Offset, ptrdiff_t _Count = dynamic_extent>
inline _LIBCPP_INLINE_VISIBILITY
constexpr span<_Tp, dynamic_extent> subspan() const noexcept
{
_LIBCPP_ASSERT(_Offset >= 0 && _Offset <= size(), "Offset out of range in span::subspan()");
_LIBCPP_ASSERT(_Count == dynamic_extent || _Offset + _Count <= size(), "Count out of range in span::subspan()");
return {data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
}
constexpr span<element_type, dynamic_extent>
inline _LIBCPP_INLINE_VISIBILITY
subspan(index_type __offset, index_type __count = dynamic_extent) const noexcept
{
_LIBCPP_ASSERT( __offset >= 0 && __offset <= size(), "Offset out of range in span::subspan(offset, count)");
_LIBCPP_ASSERT((__count >= 0 && __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(__offset + __count <= size(), "Offset + count out of range in span::subspan(offset, count)");
return {data() + __offset, __count};
}
_LIBCPP_INLINE_VISIBILITY constexpr index_type size() const noexcept { return __size; }
_LIBCPP_INLINE_VISIBILITY constexpr index_type size_bytes() const noexcept { return __size * sizeof(element_type); }
_LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; }
_LIBCPP_INLINE_VISIBILITY constexpr reference operator[](index_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T>[] index out of bounds");
return __data[__idx];
}
_LIBCPP_INLINE_VISIBILITY constexpr reference operator()(index_type __idx) const noexcept
{
_LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T>() index out of bounds");
return __data[__idx];
}
_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 const_iterator cbegin() const noexcept { return const_iterator(data()); }
_LIBCPP_INLINE_VISIBILITY constexpr const_iterator cend() const noexcept { return const_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 constexpr const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(cend()); }
_LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crend() const noexcept { return const_reverse_iterator(cbegin()); }
_LIBCPP_INLINE_VISIBILITY constexpr void swap(span &__other) noexcept
{
pointer __p = __data;
__data = __other.__data;
__other.__data = __p;
index_type __sz = __size;
__size = __other.__size;
__other.__size = __sz;
}
_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_writeable_bytes() const noexcept
{ return {reinterpret_cast<byte *>(data()), size_bytes()}; }
private:
pointer __data;
index_type __size;
};
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator==(const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return equal(__lhs.begin(), __lhs.end(), __rhs.begin(), __rhs.end()); }
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator!=(const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return !(__rhs == __lhs); }
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator< (const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return lexicographical_compare (__lhs.begin(), __lhs.end(), __rhs.begin(), __rhs.end()); }
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator<=(const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return !(__rhs < __lhs); }
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator> (const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return __rhs < __lhs; }
template <class _Tp1, ptrdiff_t _Extent1, class _Tp2, ptrdiff_t _Extent2>
constexpr bool
operator>=(const span<_Tp1, _Extent1>& __lhs, const span<_Tp2, _Extent2>& __rhs)
{ return !(__lhs < __rhs); }
// as_bytes & as_writeable_bytes
template <class _Tp, ptrdiff_t _Extent>
auto as_bytes(span<_Tp, _Extent> __s) noexcept
-> decltype(__s.__as_bytes())
{ return __s.__as_bytes(); }
template <class _Tp, ptrdiff_t _Extent>
auto as_writeable_bytes(span<_Tp, _Extent> __s) noexcept
-> typename enable_if<!is_const_v<_Tp>, decltype(__s.__as_writeable_bytes())>::type
{ return __s.__as_writeable_bytes(); }
template <class _Tp, ptrdiff_t _Extent>
constexpr void swap(span<_Tp, _Extent> &__lhs, span<_Tp, _Extent> &__rhs) noexcept
{ __lhs.swap(__rhs); }
// Deduction guides
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>;
template<class _Container>
span(_Container&) -> span<typename _Container::value_type>;
template<class _Container>
span(const _Container&) -> span<const typename _Container::value_type>;
#endif // _LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_SPAN
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