2 //===------------------------------ span ---------------------------------===//
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
8 //===---------------------------------------------------------------------===//
19 inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
21 // [views.span], class template span
22 template <class ElementType, size_t Extent = dynamic_extent>
25 // [span.objectrep], views of object representation
26 template <class ElementType, size_t Extent>
27 span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
28 (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
30 template <class ElementType, size_t Extent>
31 span< byte, ((Extent == dynamic_extent) ? dynamic_extent :
32 (sizeof(ElementType) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
36 template <class ElementType, size_t Extent = dynamic_extent>
39 // constants and types
40 using element_type = ElementType;
41 using value_type = remove_cv_t<ElementType>;
42 using size_type = size_t;
43 using difference_type = ptrdiff_t;
44 using pointer = element_type*;
45 using const_pointer = const element_type*;
46 using reference = element_type&;
47 using const_reference = const element_type&;
48 using iterator = implementation-defined;
49 using const_iterator = implementation-defined;
50 using reverse_iterator = std::reverse_iterator<iterator>;
51 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
52 static constexpr size_type extent = Extent;
54 // [span.cons], span constructors, copy, assignment, and destructor
55 constexpr span() noexcept;
56 constexpr span(pointer ptr, size_type count);
57 constexpr span(pointer firstElem, pointer lastElem);
59 constexpr span(element_type (&arr)[N]) noexcept;
61 constexpr span(array<value_type, N>& arr) noexcept;
63 constexpr span(const array<value_type, N>& arr) noexcept;
64 template <class Container>
65 constexpr span(Container& cont);
66 template <class Container>
67 constexpr span(const Container& cont);
68 constexpr span(const span& other) noexcept = default;
69 template <class OtherElementType, size_t OtherExtent>
70 constexpr span(const span<OtherElementType, OtherExtent>& s) noexcept;
71 ~span() noexcept = default;
72 constexpr span& operator=(const span& other) noexcept = default;
74 // [span.sub], span subviews
75 template <size_t Count>
76 constexpr span<element_type, Count> first() const;
77 template <size_t Count>
78 constexpr span<element_type, Count> last() const;
79 template <size_t Offset, size_t Count = dynamic_extent>
80 constexpr span<element_type, see below> subspan() const;
82 constexpr span<element_type, dynamic_extent> first(size_type count) const;
83 constexpr span<element_type, dynamic_extent> last(size_type count) const;
84 constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
86 // [span.obs], span observers
87 constexpr size_type size() const noexcept;
88 constexpr size_type size_bytes() const noexcept;
89 constexpr bool empty() const noexcept;
91 // [span.elem], span element access
92 constexpr reference operator[](size_type idx) const;
93 constexpr reference front() const;
94 constexpr reference back() const;
95 constexpr pointer data() const noexcept;
97 // [span.iterators], span iterator support
98 constexpr iterator begin() const noexcept;
99 constexpr iterator end() const noexcept;
100 constexpr const_iterator cbegin() const noexcept;
101 constexpr const_iterator cend() const noexcept;
102 constexpr reverse_iterator rbegin() const noexcept;
103 constexpr reverse_iterator rend() const noexcept;
104 constexpr const_reverse_iterator crbegin() const noexcept;
105 constexpr const_reverse_iterator crend() const noexcept;
108 pointer data_; // exposition only
109 size_type size_; // exposition only
112 template<class T, size_t N>
113 span(T (&)[N]) -> span<T, N>;
115 template<class T, size_t N>
116 span(array<T, N>&) -> span<T, N>;
118 template<class T, size_t N>
119 span(const array<T, N>&) -> span<const T, N>;
121 template<class Container>
122 span(Container&) -> span<typename Container::value_type>;
124 template<class Container>
125 span(const Container&) -> span<const typename Container::value_type>;
132 #include <cstddef> // for ptrdiff_t
133 #include <iterator> // for iterators
134 #include <array> // for array
135 #include <type_traits> // for remove_cv, etc
136 #include <cstddef> // for byte
138 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
139 #pragma GCC system_header
142 _LIBCPP_BEGIN_NAMESPACE_STD
144 #if _LIBCPP_STD_VER > 17
146 inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
147 template <typename _Tp, size_t _Extent = dynamic_extent> class span;
151 struct __is_span_impl : public false_type {};
153 template <class _Tp, size_t _Extent>
154 struct __is_span_impl<span<_Tp, _Extent>> : public true_type {};
157 struct __is_span : public __is_span_impl<remove_cv_t<_Tp>> {};
160 struct __is_std_array_impl : public false_type {};
162 template <class _Tp, size_t _Sz>
163 struct __is_std_array_impl<array<_Tp, _Sz>> : public true_type {};
166 struct __is_std_array : public __is_std_array_impl<remove_cv_t<_Tp>> {};
168 template <class _Tp, class _ElementType, class = void>
169 struct __is_span_compatible_container : public false_type {};
171 template <class _Tp, class _ElementType>
172 struct __is_span_compatible_container<_Tp, _ElementType,
174 // is not a specialization of span
175 typename enable_if<!__is_span<_Tp>::value, nullptr_t>::type,
176 // is not a specialization of array
177 typename enable_if<!__is_std_array<_Tp>::value, nullptr_t>::type,
178 // is_array_v<Container> is false,
179 typename enable_if<!is_array_v<_Tp>, nullptr_t>::type,
180 // data(cont) and size(cont) are well formed
181 decltype(data(declval<_Tp>())),
182 decltype(size(declval<_Tp>())),
183 // remove_pointer_t<decltype(data(cont))>(*)[] is convertible to ElementType(*)[]
185 is_convertible_v<remove_pointer_t<decltype(data(declval<_Tp &>()))>(*)[],
189 : public true_type {};
192 template <typename _Tp, size_t _Extent>
193 class _LIBCPP_TEMPLATE_VIS span {
195 // constants and types
196 using element_type = _Tp;
197 using value_type = remove_cv_t<_Tp>;
198 using size_type = size_t;
199 using difference_type = ptrdiff_t;
200 using pointer = _Tp *;
201 using const_pointer = const _Tp *;
202 using reference = _Tp &;
203 using const_reference = const _Tp &;
204 using iterator = __wrap_iter<pointer>;
205 using const_iterator = __wrap_iter<const_pointer>;
206 using reverse_iterator = _VSTD::reverse_iterator<iterator>;
207 using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
209 static constexpr size_type extent = _Extent;
211 // [span.cons], span constructors, copy, assignment, and destructor
212 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}
213 { static_assert(_Extent == 0, "Can't default construct a statically sized span with size > 0"); }
215 constexpr span (const span&) noexcept = default;
216 constexpr span& operator=(const span&) noexcept = default;
218 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}
219 { (void)__count; _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (ptr, len)"); }
220 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}
221 { (void)__l; _LIBCPP_ASSERT(_Extent == distance(__f, __l), "size mismatch in span's constructor (ptr, ptr)"); }
223 _LIBCPP_INLINE_VISIBILITY constexpr span(element_type (&__arr)[_Extent]) noexcept : __data{__arr} {}
224 _LIBCPP_INLINE_VISIBILITY constexpr span( array<value_type, _Extent>& __arr) noexcept : __data{__arr.data()} {}
225 _LIBCPP_INLINE_VISIBILITY constexpr span(const array<value_type, _Extent>& __arr) noexcept : __data{__arr.data()} {}
227 template <class _OtherElementType>
228 _LIBCPP_INLINE_VISIBILITY
229 constexpr span(const span<_OtherElementType, _Extent>& __other,
231 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
232 nullptr_t> = nullptr)
233 : __data{__other.data()} {}
235 template <class _OtherElementType>
236 _LIBCPP_INLINE_VISIBILITY
237 constexpr span(const span<_OtherElementType, dynamic_extent>& __other,
239 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
240 nullptr_t> = nullptr) noexcept
241 : __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); }
244 // ~span() noexcept = default;
246 template <size_t _Count>
247 _LIBCPP_INLINE_VISIBILITY
248 constexpr span<element_type, _Count> first() const noexcept
250 static_assert(_Count <= _Extent, "Count out of range in span::first()");
251 return {data(), _Count};
254 template <size_t _Count>
255 _LIBCPP_INLINE_VISIBILITY
256 constexpr span<element_type, _Count> last() const noexcept
258 static_assert(_Count <= _Extent, "Count out of range in span::last()");
259 return {data() + size() - _Count, _Count};
262 _LIBCPP_INLINE_VISIBILITY
263 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
265 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
266 return {data(), __count};
269 _LIBCPP_INLINE_VISIBILITY
270 constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept
272 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
273 return {data() + size() - __count, __count};
276 template <size_t _Offset, size_t _Count = dynamic_extent>
277 _LIBCPP_INLINE_VISIBILITY
278 constexpr auto subspan() const noexcept
279 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>
281 static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()");
282 return {data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
286 _LIBCPP_INLINE_VISIBILITY
287 constexpr span<element_type, dynamic_extent>
288 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
290 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
291 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)");
292 if (__count == dynamic_extent)
293 return {data() + __offset, size() - __offset};
294 _LIBCPP_ASSERT(__offset <= size() - __count, "count + offset out of range in span::subspan(offset, count)");
295 return {data() + __offset, __count};
298 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; }
299 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
300 _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; }
302 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
304 _LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T,N>[] index out of bounds");
305 return __data[__idx];
308 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
310 static_assert(_Extent > 0, "span<T,N>[].front() on empty span");
314 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
316 static_assert(_Extent > 0, "span<T,N>[].back() on empty span");
317 return __data[size()-1];
320 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
322 // [span.iter], span iterator support
323 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
324 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
325 _LIBCPP_INLINE_VISIBILITY constexpr const_iterator cbegin() const noexcept { return const_iterator(data()); }
326 _LIBCPP_INLINE_VISIBILITY constexpr const_iterator cend() const noexcept { return const_iterator(data() + size()); }
327 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
328 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
329 _LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(cend()); }
330 _LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crend() const noexcept { return const_reverse_iterator(cbegin()); }
332 _LIBCPP_INLINE_VISIBILITY constexpr void swap(span &__other) noexcept
334 pointer __p = __data;
335 __data = __other.__data;
336 __other.__data = __p;
339 _LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept
340 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; }
342 _LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept
343 { return {reinterpret_cast<byte *>(data()), size_bytes()}; }
351 template <typename _Tp>
352 class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
356 // constants and types
357 using element_type = _Tp;
358 using value_type = remove_cv_t<_Tp>;
359 using size_type = size_t;
360 using difference_type = ptrdiff_t;
361 using pointer = _Tp *;
362 using const_pointer = const _Tp *;
363 using reference = _Tp &;
364 using const_reference = const _Tp &;
365 using iterator = __wrap_iter<pointer>;
366 using const_iterator = __wrap_iter<const_pointer>;
367 using reverse_iterator = _VSTD::reverse_iterator<iterator>;
368 using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
370 static constexpr size_type extent = dynamic_extent;
372 // [span.cons], span constructors, copy, assignment, and destructor
373 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {}
375 constexpr span (const span&) noexcept = default;
376 constexpr span& operator=(const span&) noexcept = default;
378 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}, __size{__count} {}
379 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}, __size{static_cast<size_t>(distance(__f, __l))} {}
381 template <size_t _Sz>
382 _LIBCPP_INLINE_VISIBILITY
383 constexpr span(element_type (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {}
385 template <size_t _Sz>
386 _LIBCPP_INLINE_VISIBILITY
387 constexpr span(array<value_type, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
389 template <size_t _Sz>
390 _LIBCPP_INLINE_VISIBILITY
391 constexpr span(const array<value_type, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
393 template <class _Container>
394 _LIBCPP_INLINE_VISIBILITY
395 constexpr span( _Container& __c,
396 enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
397 : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
399 template <class _Container>
400 _LIBCPP_INLINE_VISIBILITY
401 constexpr span(const _Container& __c,
402 enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
403 : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
406 template <class _OtherElementType, size_t _OtherExtent>
407 _LIBCPP_INLINE_VISIBILITY
408 constexpr span(const span<_OtherElementType, _OtherExtent>& __other,
410 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
411 nullptr_t> = nullptr) noexcept
412 : __data{__other.data()}, __size{__other.size()} {}
414 // ~span() noexcept = default;
416 template <size_t _Count>
417 _LIBCPP_INLINE_VISIBILITY
418 constexpr span<element_type, _Count> first() const noexcept
420 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()");
421 return {data(), _Count};
424 template <size_t _Count>
425 _LIBCPP_INLINE_VISIBILITY
426 constexpr span<element_type, _Count> last() const noexcept
428 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()");
429 return {data() + size() - _Count, _Count};
432 _LIBCPP_INLINE_VISIBILITY
433 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
435 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
436 return {data(), __count};
439 _LIBCPP_INLINE_VISIBILITY
440 constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept
442 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
443 return {data() + size() - __count, __count};
446 template <size_t _Offset, size_t _Count = dynamic_extent>
447 _LIBCPP_INLINE_VISIBILITY
448 constexpr span<_Tp, dynamic_extent> subspan() const noexcept
450 _LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()");
451 _LIBCPP_ASSERT(_Count == dynamic_extent || _Offset + _Count <= size(), "Count out of range in span::subspan()");
452 return {data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
455 constexpr span<element_type, dynamic_extent>
456 _LIBCPP_INLINE_VISIBILITY
457 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
459 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
460 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)");
461 if (__count == dynamic_extent)
462 return {data() + __offset, size() - __offset};
463 _LIBCPP_ASSERT(__offset <= size() - __count, "Offset + count out of range in span::subspan(offset, count)");
464 return {data() + __offset, __count};
467 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; }
468 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); }
469 _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; }
471 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
473 _LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T>[] index out of bounds");
474 return __data[__idx];
477 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
479 _LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span");
483 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
485 _LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span");
486 return __data[size()-1];
490 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
492 // [span.iter], span iterator support
493 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
494 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
495 _LIBCPP_INLINE_VISIBILITY constexpr const_iterator cbegin() const noexcept { return const_iterator(data()); }
496 _LIBCPP_INLINE_VISIBILITY constexpr const_iterator cend() const noexcept { return const_iterator(data() + size()); }
497 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
498 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
499 _LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(cend()); }
500 _LIBCPP_INLINE_VISIBILITY constexpr const_reverse_iterator crend() const noexcept { return const_reverse_iterator(cbegin()); }
502 _LIBCPP_INLINE_VISIBILITY constexpr void swap(span &__other) noexcept
504 pointer __p = __data;
505 __data = __other.__data;
506 __other.__data = __p;
508 size_type __sz = __size;
509 __size = __other.__size;
510 __other.__size = __sz;
513 _LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept
514 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; }
516 _LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept
517 { return {reinterpret_cast<byte *>(data()), size_bytes()}; }
525 template <class _Tp, size_t _Size>
526 struct _LIBCPP_TEMPLATE_VIS tuple_size<span<_Tp, _Size>>
527 : public integral_constant<size_t, _Size> {};
530 struct _LIBCPP_TEMPLATE_VIS tuple_size<span<_Tp, dynamic_extent>>; // declared but not defined
533 template <size_t _Ip, class _Tp, size_t _Size>
534 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, span<_Tp, _Size>>
536 static_assert( dynamic_extent != _Size, "std::tuple_element<> not supported for std::span<T, dynamic_extent>");
537 static_assert(_Ip < _Size, "Index out of bounds in std::tuple_element<> (std::span)");
541 template <size_t _Ip, class _Tp, size_t _Size>
542 _LIBCPP_INLINE_VISIBILITY constexpr
544 get(span<_Tp, _Size> __s) noexcept
546 static_assert( dynamic_extent != _Size, "std::get<> not supported for std::span<T, dynamic_extent>");
547 static_assert(_Ip < _Size, "Index out of bounds in std::get<> (std::span)");
552 // as_bytes & as_writable_bytes
553 template <class _Tp, size_t _Extent>
554 _LIBCPP_INLINE_VISIBILITY
555 auto as_bytes(span<_Tp, _Extent> __s) noexcept
556 -> decltype(__s.__as_bytes())
557 { return __s.__as_bytes(); }
559 template <class _Tp, size_t _Extent>
560 _LIBCPP_INLINE_VISIBILITY
561 auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept
562 -> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())>
563 { return __s.__as_writable_bytes(); }
565 template <class _Tp, size_t _Extent>
566 _LIBCPP_INLINE_VISIBILITY
567 constexpr void swap(span<_Tp, _Extent> &__lhs, span<_Tp, _Extent> &__rhs) noexcept
568 { __lhs.swap(__rhs); }
572 template<class _Tp, size_t _Sz>
573 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
575 template<class _Tp, size_t _Sz>
576 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
578 template<class _Tp, size_t _Sz>
579 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
581 template<class _Container>
582 span(_Container&) -> span<typename _Container::value_type>;
584 template<class _Container>
585 span(const _Container&) -> span<const typename _Container::value_type>;
587 #endif // _LIBCPP_STD_VER > 17
589 _LIBCPP_END_NAMESPACE_STD
591 #endif // _LIBCPP_SPAN