1 // Components for manipulating non-owning sequences of characters -*- C++ -*-
3 // Copyright (C) 2013-2023 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file include/string_view
26 * This is a Standard C++ Library header.
30 // N3762 basic_string_view library
33 #ifndef _GLIBCXX_STRING_VIEW
34 #define _GLIBCXX_STRING_VIEW 1
36 #pragma GCC system_header
38 #define __glibcxx_want_constexpr_char_traits
39 #define __glibcxx_want_string_view
40 #define __glibcxx_want_constexpr_string_view
41 #define __glibcxx_want_starts_ends_with
42 #define __glibcxx_want_string_contains
43 #include <bits/version.h>
45 #if __cplusplus >= 201703L
47 #include <bits/char_traits.h>
48 #include <bits/functexcept.h>
49 #include <bits/functional_hash.h>
50 #include <bits/range_access.h>
51 #include <bits/stl_algobase.h>
52 #include <ext/numeric_traits.h>
54 #if __cplusplus >= 202002L
55 # include <bits/ranges_base.h>
60 # include <bits/ostream_insert.h>
63 namespace std _GLIBCXX_VISIBILITY(default)
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
67 // Helper for basic_string and basic_string_view members.
69 __sv_check(size_t __size, size_t __pos, const char* __s)
72 __throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > __size "
73 "(which is %zu)"), __s, __pos, __size);
77 // Helper for basic_string members.
78 // NB: __sv_limit doesn't check for a bad __pos value.
80 __sv_limit(size_t __size, size_t __pos, size_t __off) noexcept
82 const bool __testoff = __off < __size - __pos;
83 return __testoff ? __off : __size - __pos;
87 * @class basic_string_view <string_view>
88 * @brief A non-owning reference to a string.
93 * @tparam _CharT Type of character
94 * @tparam _Traits Traits for character type, defaults to
95 * char_traits<_CharT>.
97 * A basic_string_view looks like this:
104 template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
105 class basic_string_view
107 static_assert(!is_array_v<_CharT>);
108 static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>);
109 static_assert(is_same_v<_CharT, typename _Traits::char_type>);
114 using traits_type = _Traits;
115 using value_type = _CharT;
116 using pointer = value_type*;
117 using const_pointer = const value_type*;
118 using reference = value_type&;
119 using const_reference = const value_type&;
120 using const_iterator = const value_type*;
121 using iterator = const_iterator;
122 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
123 using reverse_iterator = const_reverse_iterator;
124 using size_type = size_t;
125 using difference_type = ptrdiff_t;
126 static constexpr size_type npos = size_type(-1);
128 // [string.view.cons], construction and assignment
131 basic_string_view() noexcept
132 : _M_len{0}, _M_str{nullptr}
135 constexpr basic_string_view(const basic_string_view&) noexcept = default;
137 [[__gnu__::__nonnull__]]
139 basic_string_view(const _CharT* __str) noexcept
140 : _M_len{traits_type::length(__str)},
145 basic_string_view(const _CharT* __str, size_type __len) noexcept
146 : _M_len{__len}, _M_str{__str}
149 #if __cplusplus >= 202002L && __cpp_lib_concepts
150 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
151 requires same_as<iter_value_t<_It>, _CharT>
152 && (!convertible_to<_End, size_type>)
154 basic_string_view(_It __first, _End __last)
155 noexcept(noexcept(__last - __first))
156 : _M_len(__last - __first), _M_str(std::to_address(__first))
159 #if __cplusplus > 202002L
160 template<typename _Range, typename _DRange = remove_cvref_t<_Range>>
161 requires (!is_same_v<_DRange, basic_string_view>)
162 && ranges::contiguous_range<_Range>
163 && ranges::sized_range<_Range>
164 && is_same_v<ranges::range_value_t<_Range>, _CharT>
165 && (!is_convertible_v<_Range, const _CharT*>)
166 && (!requires (_DRange& __d) {
167 __d.operator ::std::basic_string_view<_CharT, _Traits>();
169 && (!requires { typename _DRange::traits_type; }
170 || is_same_v<typename _DRange::traits_type, _Traits>)
172 basic_string_view(_Range&& __r)
173 noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r)))
174 : _M_len(ranges::size(__r)), _M_str(ranges::data(__r))
177 basic_string_view(nullptr_t) = delete;
181 constexpr basic_string_view&
182 operator=(const basic_string_view&) noexcept = default;
184 // [string.view.iterators], iterator support
187 constexpr const_iterator
188 begin() const noexcept
189 { return this->_M_str; }
192 constexpr const_iterator
194 { return this->_M_str + this->_M_len; }
197 constexpr const_iterator
198 cbegin() const noexcept
199 { return this->_M_str; }
202 constexpr const_iterator
203 cend() const noexcept
204 { return this->_M_str + this->_M_len; }
207 constexpr const_reverse_iterator
208 rbegin() const noexcept
209 { return const_reverse_iterator(this->end()); }
212 constexpr const_reverse_iterator
213 rend() const noexcept
214 { return const_reverse_iterator(this->begin()); }
217 constexpr const_reverse_iterator
218 crbegin() const noexcept
219 { return const_reverse_iterator(this->end()); }
222 constexpr const_reverse_iterator
223 crend() const noexcept
224 { return const_reverse_iterator(this->begin()); }
226 // [string.view.capacity], capacity
230 size() const noexcept
231 { return this->_M_len; }
235 length() const noexcept
240 max_size() const noexcept
242 return (npos - sizeof(size_type) - sizeof(void*))
243 / sizeof(value_type) / 4;
248 empty() const noexcept
249 { return this->_M_len == 0; }
251 // [string.view.access], element access
254 constexpr const_reference
255 operator[](size_type __pos) const noexcept
257 __glibcxx_assert(__pos < this->_M_len);
258 return *(this->_M_str + __pos);
262 constexpr const_reference
263 at(size_type __pos) const
266 __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
267 "(which is %zu) >= this->size() "
268 "(which is %zu)"), __pos, this->size());
269 return *(this->_M_str + __pos);
273 constexpr const_reference
274 front() const noexcept
276 __glibcxx_assert(this->_M_len > 0);
277 return *this->_M_str;
281 constexpr const_reference
282 back() const noexcept
284 __glibcxx_assert(this->_M_len > 0);
285 return *(this->_M_str + this->_M_len - 1);
289 constexpr const_pointer
290 data() const noexcept
291 { return this->_M_str; }
293 // [string.view.modifiers], modifiers:
296 remove_prefix(size_type __n) noexcept
298 __glibcxx_assert(this->_M_len >= __n);
304 remove_suffix(size_type __n) noexcept
306 __glibcxx_assert(this->_M_len >= __n);
311 swap(basic_string_view& __sv) noexcept
318 // [string.view.ops], string operations:
322 copy(_CharT* __str, size_type __n, size_type __pos = 0) const
324 __glibcxx_requires_string_len(__str, __n);
325 __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
326 const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
327 // _GLIBCXX_RESOLVE_LIB_DEFECTS
328 // 2777. basic_string_view::copy should use char_traits::copy
329 traits_type::copy(__str, data() + __pos, __rlen);
334 constexpr basic_string_view
335 substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
337 __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
338 const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
339 return basic_string_view{_M_str + __pos, __rlen};
344 compare(basic_string_view __str) const noexcept
346 const size_type __rlen = std::min(this->_M_len, __str._M_len);
347 int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
349 __ret = _S_compare(this->_M_len, __str._M_len);
355 compare(size_type __pos1, size_type __n1, basic_string_view __str) const
356 { return this->substr(__pos1, __n1).compare(__str); }
360 compare(size_type __pos1, size_type __n1,
361 basic_string_view __str, size_type __pos2, size_type __n2) const
363 return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
366 [[nodiscard, __gnu__::__nonnull__]]
368 compare(const _CharT* __str) const noexcept
369 { return this->compare(basic_string_view{__str}); }
371 [[nodiscard, __gnu__::__nonnull__]]
373 compare(size_type __pos1, size_type __n1, const _CharT* __str) const
374 { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
378 compare(size_type __pos1, size_type __n1,
379 const _CharT* __str, size_type __n2) const noexcept(false)
381 return this->substr(__pos1, __n1)
382 .compare(basic_string_view(__str, __n2));
385 #ifdef __cpp_lib_starts_ends_with // C++ >= 20
388 starts_with(basic_string_view __x) const noexcept
389 { return this->substr(0, __x.size()) == __x; }
393 starts_with(_CharT __x) const noexcept
394 { return !this->empty() && traits_type::eq(this->front(), __x); }
396 [[nodiscard, __gnu__::__nonnull__]]
398 starts_with(const _CharT* __x) const noexcept
399 { return this->starts_with(basic_string_view(__x)); }
403 ends_with(basic_string_view __x) const noexcept
405 const auto __len = this->size();
406 const auto __xlen = __x.size();
407 return __len >= __xlen
408 && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
413 ends_with(_CharT __x) const noexcept
414 { return !this->empty() && traits_type::eq(this->back(), __x); }
416 [[nodiscard, __gnu__::__nonnull__]]
418 ends_with(const _CharT* __x) const noexcept
419 { return this->ends_with(basic_string_view(__x)); }
420 #endif // __cpp_lib_starts_ends_with
422 #if __cplusplus > 202002L
423 #if _GLIBCXX_HOSTED && !defined(__cpp_lib_string_contains)
424 // This FTM is not freestanding as it also implies matching <string>
425 // support, and <string> is omitted from the freestanding subset.
426 # error "libstdc++ bug: string_contains not defined when it should be"
430 contains(basic_string_view __x) const noexcept
431 { return this->find(__x) != npos; }
435 contains(_CharT __x) const noexcept
436 { return this->find(__x) != npos; }
438 [[nodiscard, __gnu__::__nonnull__]]
440 contains(const _CharT* __x) const noexcept
441 { return this->find(__x) != npos; }
444 // [string.view.find], searching
448 find(basic_string_view __str, size_type __pos = 0) const noexcept
449 { return this->find(__str._M_str, __pos, __str._M_len); }
453 find(_CharT __c, size_type __pos = 0) const noexcept;
457 find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
459 [[nodiscard, __gnu__::__nonnull__]]
461 find(const _CharT* __str, size_type __pos = 0) const noexcept
462 { return this->find(__str, __pos, traits_type::length(__str)); }
466 rfind(basic_string_view __str, size_type __pos = npos) const noexcept
467 { return this->rfind(__str._M_str, __pos, __str._M_len); }
471 rfind(_CharT __c, size_type __pos = npos) const noexcept;
475 rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
477 [[nodiscard, __gnu__::__nonnull__]]
479 rfind(const _CharT* __str, size_type __pos = npos) const noexcept
480 { return this->rfind(__str, __pos, traits_type::length(__str)); }
484 find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
485 { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
489 find_first_of(_CharT __c, size_type __pos = 0) const noexcept
490 { return this->find(__c, __pos); }
494 find_first_of(const _CharT* __str, size_type __pos,
495 size_type __n) const noexcept;
497 [[nodiscard, __gnu__::__nonnull__]]
499 find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
500 { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
504 find_last_of(basic_string_view __str,
505 size_type __pos = npos) const noexcept
506 { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
510 find_last_of(_CharT __c, size_type __pos=npos) const noexcept
511 { return this->rfind(__c, __pos); }
515 find_last_of(const _CharT* __str, size_type __pos,
516 size_type __n) const noexcept;
518 [[nodiscard, __gnu__::__nonnull__]]
520 find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
521 { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
525 find_first_not_of(basic_string_view __str,
526 size_type __pos = 0) const noexcept
527 { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
531 find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
535 find_first_not_of(const _CharT* __str,
536 size_type __pos, size_type __n) const noexcept;
538 [[nodiscard, __gnu__::__nonnull__]]
540 find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
542 return this->find_first_not_of(__str, __pos,
543 traits_type::length(__str));
548 find_last_not_of(basic_string_view __str,
549 size_type __pos = npos) const noexcept
550 { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
554 find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
558 find_last_not_of(const _CharT* __str,
559 size_type __pos, size_type __n) const noexcept;
561 [[nodiscard, __gnu__::__nonnull__]]
563 find_last_not_of(const _CharT* __str,
564 size_type __pos = npos) const noexcept
566 return this->find_last_not_of(__str, __pos,
567 traits_type::length(__str));
573 _S_compare(size_type __n1, size_type __n2) noexcept
575 using __limits = __gnu_cxx::__int_traits<int>;
576 const difference_type __diff = __n1 - __n2;
577 if (__diff > __limits::__max)
578 return __limits::__max;
579 if (__diff < __limits::__min)
580 return __limits::__min;
581 return static_cast<int>(__diff);
585 const _CharT* _M_str;
588 #if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
589 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
590 basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
592 #if __cplusplus > 202002L
593 template<ranges::contiguous_range _Range>
594 basic_string_view(_Range&&)
595 -> basic_string_view<ranges::range_value_t<_Range>>;
599 // [string.view.comparison], non-member basic_string_view comparison function
601 // Several of these functions use type_identity_t to create a non-deduced
602 // context, so that only one argument participates in template argument
603 // deduction and the other argument gets implicitly converted to the deduced
606 template<typename _CharT, typename _Traits>
609 operator==(basic_string_view<_CharT, _Traits> __x,
610 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
612 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
614 #if __cpp_lib_three_way_comparison
615 template<typename _CharT, typename _Traits>
618 operator<=>(basic_string_view<_CharT, _Traits> __x,
619 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
621 -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
622 { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
624 template<typename _CharT, typename _Traits>
627 operator==(basic_string_view<_CharT, _Traits> __x,
628 basic_string_view<_CharT, _Traits> __y) noexcept
629 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
631 template<typename _CharT, typename _Traits>
634 operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
635 basic_string_view<_CharT, _Traits> __y) noexcept
636 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
638 template<typename _CharT, typename _Traits>
641 operator!=(basic_string_view<_CharT, _Traits> __x,
642 basic_string_view<_CharT, _Traits> __y) noexcept
643 { return !(__x == __y); }
645 template<typename _CharT, typename _Traits>
648 operator!=(basic_string_view<_CharT, _Traits> __x,
649 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
651 { return !(__x == __y); }
653 template<typename _CharT, typename _Traits>
656 operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
657 basic_string_view<_CharT, _Traits> __y) noexcept
658 { return !(__x == __y); }
660 template<typename _CharT, typename _Traits>
663 operator< (basic_string_view<_CharT, _Traits> __x,
664 basic_string_view<_CharT, _Traits> __y) noexcept
665 { return __x.compare(__y) < 0; }
667 template<typename _CharT, typename _Traits>
670 operator< (basic_string_view<_CharT, _Traits> __x,
671 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
673 { return __x.compare(__y) < 0; }
675 template<typename _CharT, typename _Traits>
678 operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
679 basic_string_view<_CharT, _Traits> __y) noexcept
680 { return __x.compare(__y) < 0; }
682 template<typename _CharT, typename _Traits>
685 operator> (basic_string_view<_CharT, _Traits> __x,
686 basic_string_view<_CharT, _Traits> __y) noexcept
687 { return __x.compare(__y) > 0; }
689 template<typename _CharT, typename _Traits>
692 operator> (basic_string_view<_CharT, _Traits> __x,
693 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
695 { return __x.compare(__y) > 0; }
697 template<typename _CharT, typename _Traits>
700 operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
701 basic_string_view<_CharT, _Traits> __y) noexcept
702 { return __x.compare(__y) > 0; }
704 template<typename _CharT, typename _Traits>
707 operator<=(basic_string_view<_CharT, _Traits> __x,
708 basic_string_view<_CharT, _Traits> __y) noexcept
709 { return __x.compare(__y) <= 0; }
711 template<typename _CharT, typename _Traits>
714 operator<=(basic_string_view<_CharT, _Traits> __x,
715 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
717 { return __x.compare(__y) <= 0; }
719 template<typename _CharT, typename _Traits>
722 operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
723 basic_string_view<_CharT, _Traits> __y) noexcept
724 { return __x.compare(__y) <= 0; }
726 template<typename _CharT, typename _Traits>
729 operator>=(basic_string_view<_CharT, _Traits> __x,
730 basic_string_view<_CharT, _Traits> __y) noexcept
731 { return __x.compare(__y) >= 0; }
733 template<typename _CharT, typename _Traits>
736 operator>=(basic_string_view<_CharT, _Traits> __x,
737 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
739 { return __x.compare(__y) >= 0; }
741 template<typename _CharT, typename _Traits>
744 operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
745 basic_string_view<_CharT, _Traits> __y) noexcept
746 { return __x.compare(__y) >= 0; }
747 #endif // three-way comparison
750 // [string.view.io], Inserters and extractors
751 template<typename _CharT, typename _Traits>
752 inline basic_ostream<_CharT, _Traits>&
753 operator<<(basic_ostream<_CharT, _Traits>& __os,
754 basic_string_view<_CharT,_Traits> __str)
755 { return __ostream_insert(__os, __str.data(), __str.size()); }
758 // basic_string_view typedef names
760 using string_view = basic_string_view<char>;
761 using wstring_view = basic_string_view<wchar_t>;
762 #ifdef _GLIBCXX_USE_CHAR8_T
763 using u8string_view = basic_string_view<char8_t>;
765 using u16string_view = basic_string_view<char16_t>;
766 using u32string_view = basic_string_view<char32_t>;
768 // [string.view.hash], hash support:
770 template<typename _Tp>
774 struct hash<string_view>
775 : public __hash_base<size_t, string_view>
779 operator()(const string_view& __str) const noexcept
780 { return std::_Hash_impl::hash(__str.data(), __str.length()); }
784 struct __is_fast_hash<hash<string_view>> : std::false_type
788 struct hash<wstring_view>
789 : public __hash_base<size_t, wstring_view>
793 operator()(const wstring_view& __s) const noexcept
794 { return std::_Hash_impl::hash(__s.data(),
795 __s.length() * sizeof(wchar_t)); }
799 struct __is_fast_hash<hash<wstring_view>> : std::false_type
802 #ifdef _GLIBCXX_USE_CHAR8_T
804 struct hash<u8string_view>
805 : public __hash_base<size_t, u8string_view>
809 operator()(const u8string_view& __str) const noexcept
810 { return std::_Hash_impl::hash(__str.data(), __str.length()); }
814 struct __is_fast_hash<hash<u8string_view>> : std::false_type
819 struct hash<u16string_view>
820 : public __hash_base<size_t, u16string_view>
824 operator()(const u16string_view& __s) const noexcept
825 { return std::_Hash_impl::hash(__s.data(),
826 __s.length() * sizeof(char16_t)); }
830 struct __is_fast_hash<hash<u16string_view>> : std::false_type
834 struct hash<u32string_view>
835 : public __hash_base<size_t, u32string_view>
839 operator()(const u32string_view& __s) const noexcept
840 { return std::_Hash_impl::hash(__s.data(),
841 __s.length() * sizeof(char32_t)); }
845 struct __is_fast_hash<hash<u32string_view>> : std::false_type
848 inline namespace literals
850 inline namespace string_view_literals
852 #pragma GCC diagnostic push
853 #pragma GCC diagnostic ignored "-Wliteral-suffix"
854 inline constexpr basic_string_view<char>
855 operator""sv(const char* __str, size_t __len) noexcept
856 { return basic_string_view<char>{__str, __len}; }
858 inline constexpr basic_string_view<wchar_t>
859 operator""sv(const wchar_t* __str, size_t __len) noexcept
860 { return basic_string_view<wchar_t>{__str, __len}; }
862 #ifdef _GLIBCXX_USE_CHAR8_T
863 inline constexpr basic_string_view<char8_t>
864 operator""sv(const char8_t* __str, size_t __len) noexcept
865 { return basic_string_view<char8_t>{__str, __len}; }
868 inline constexpr basic_string_view<char16_t>
869 operator""sv(const char16_t* __str, size_t __len) noexcept
870 { return basic_string_view<char16_t>{__str, __len}; }
872 inline constexpr basic_string_view<char32_t>
873 operator""sv(const char32_t* __str, size_t __len) noexcept
874 { return basic_string_view<char32_t>{__str, __len}; }
876 #pragma GCC diagnostic pop
877 } // namespace string_literals
878 } // namespace literals
880 #if __cpp_lib_concepts
883 // Opt-in to borrowed_range concept
884 template<typename _CharT, typename _Traits>
885 inline constexpr bool
886 enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
888 // Opt-in to view concept
889 template<typename _CharT, typename _Traits>
890 inline constexpr bool
891 enable_view<basic_string_view<_CharT, _Traits>> = true;
894 _GLIBCXX_END_NAMESPACE_VERSION
897 #include <bits/string_view.tcc>
899 #endif // __cplusplus <= 201402L
901 #endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW