| // -*- C++ -*- | 
 | //===------------------------------ span ---------------------------------===// | 
 | // | 
 | // 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; | 
 |  | 
 | // [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; | 
 |  | 
 |  | 
 | 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; | 
 |  | 
 |     // [span.cons], span constructors, copy, assignment, and destructor | 
 |     constexpr span() noexcept; | 
 |     constexpr explicit(Extent != dynamic_extent) span(pointer ptr, size_type count); | 
 |     constexpr explicit(Extent != dynamic_extent) 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 explicit(Extent != dynamic_extent) span(Container& cont); | 
 |     template <class Container> | 
 |         constexpr explicit(Extent != dynamic_extent) span(const Container& cont); | 
 |     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; | 
 |     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 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 <array>        // for array | 
 | #include <cstddef>      // for byte | 
 | #include <iterator>     // for iterators | 
 | #include <type_traits>  // for remove_cv, etc | 
 |  | 
 | #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 | 
 |  | 
 | inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max(); | 
 | template <typename _Tp, size_t _Extent = dynamic_extent> class span; | 
 |  | 
 |  | 
 | template <class _Tp> | 
 | struct __is_span_impl : public false_type {}; | 
 |  | 
 | template <class _Tp, size_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, 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 &; | 
 |     using iterator               =  __wrap_iter<pointer>; | 
 |     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; | 
 |  | 
 |     _LIBCPP_INLINE_VISIBILITY constexpr explicit span(pointer __ptr, size_type __count) : __data{__ptr} | 
 |         { (void)__count; _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (ptr, len)"); } | 
 |     _LIBCPP_INLINE_VISIBILITY constexpr explicit 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} {} | 
 |  | 
 |     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()} {} | 
 |  | 
 |     template <class _Container> | 
 |     _LIBCPP_INLINE_VISIBILITY | 
 |         constexpr explicit 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 (range)"); | 
 |         } | 
 |  | 
 |     template <class _Container> | 
 |     _LIBCPP_INLINE_VISIBILITY | 
 |         constexpr explicit 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 (range)"); | 
 |         } | 
 |  | 
 |     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); } | 
 |     _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 &; | 
 |     using iterator               =  __wrap_iter<pointer>; | 
 |     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; | 
 |  | 
 |     _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}, __size{__count} {} | 
 |     _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}, __size{static_cast<size_t>(distance(__f, __l))} {} | 
 |  | 
 |     template <size_t _Sz> | 
 |     _LIBCPP_INLINE_VISIBILITY | 
 |     constexpr span(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} {} | 
 |  | 
 |     template <class _Container> | 
 |     _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{(size_type) _VSTD::size(__c)} {} | 
 |  | 
 |     template <class _Container> | 
 |     _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{(size_type) _VSTD::size(__c)} {} | 
 |  | 
 |  | 
 |     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); } | 
 |     _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; | 
 | }; | 
 |  | 
 | //  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(); } | 
 |  | 
 | //  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 | 
 |  | 
 | _LIBCPP_POP_MACROS | 
 |  | 
 | #endif // _LIBCPP_SPAN |