basic_string.h source code [include/c++/12/bits/basic_string.h]

1	// Components for manipulating sequences of characters -- C++ --
2
3	// Copyright (C) 1997-2022 Free Software Foundation, Inc.
4	//
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)
9	// any later version.
10
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.
15
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.
19
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/>.
24
25	/* @file bits/basic_string.h*
26	* This is an internal header file, included by other library headers.
27	* Do not attempt to use it directly. @headername{string}
28	*/
29
30	//
31	// ISO C++ 14882: 21 Strings library
32	//
33
34	#ifndef _BASIC_STRING_H
35	#define _BASIC_STRING_H 1
36
37	#pragma GCC system_header
38
39	#include <ext/alloc_traits.h>
40	#include <debug/debug.h>
41
42	#if __cplusplus >= 201103L
43	#include <initializer_list>
44	#endif
45
46	#if __cplusplus >= 201703L
47	# include <string_view>
48	#endif
49
50	#if ! _GLIBCXX_USE_CXX11_ABI
51	# include "cow_string.h"
52	#else
53	namespace std _GLIBCXX_VISIBILITY(default)
54	{
55	_GLIBCXX_BEGIN_NAMESPACE_VERSION
56	_GLIBCXX_BEGIN_NAMESPACE_CXX11
57
58	#ifdef __cpp_lib_is_constant_evaluated
59	// Support P0980R1 in C++20.
60	# define __cpp_lib_constexpr_string 201907L
61	#elif __cplusplus >= 201703L && _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
62	// Support P0426R1 changes to char_traits in C++17.
63	# define __cpp_lib_constexpr_string 201611L
64	#endif
65
66	/**
67	* @class basic_string basic_string.h <string>
68	* @brief Managing sequences of characters and character-like objects.
69	*
70	* @ingroup strings
71	* @ingroup sequences
72	*
73	* @tparam _CharT Type of character
74	* @tparam _Traits Traits for character type, defaults to
75	* char_traits<_CharT>.
76	* @tparam _Alloc Allocator type, defaults to allocator<_CharT>.
77	*
78	* Meets the requirements of a <a href="tables.html#65">container</a>, a
79	* <a href="tables.html#66">reversible container</a>, and a
80	* <a href="tables.html#67">sequence</a>. Of the
81	* <a href="tables.html#68">optional sequence requirements</a>, only
82	* @c push_back, @c at, and @c %array access are supported.
83	*/
84	template<typename _CharT, typename _Traits, typename _Alloc>
85	class basic_string
86	{
87	typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
88	rebind<_CharT>::other _Char_alloc_type;
89
90	#if __cpp_lib_constexpr_string < 201907L
91	typedef __gnu_cxx::__alloc_traits<_Char_alloc_type> _Alloc_traits;
92	#else
93	template<typename _Traits2, typename _Dummy_for_PR85282>
94	struct _Alloc_traits_impl : __gnu_cxx::__alloc_traits<_Char_alloc_type>
95	{
96	typedef __gnu_cxx::__alloc_traits<_Char_alloc_type> _Base;
97
98	[[__gnu__::__always_inline__]]
99	static constexpr typename _Base::pointer
100	allocate(_Char_alloc_type& __a, typename _Base::size_type __n)
101	{
102	pointer __p = _Base::allocate(__a, __n);
103	if (std::is_constant_evaluated())
104	// Begin the lifetime of characters in allocated storage.
105	for (size_type __i = `0`; __i < __n; ++__i)
106	std::construct_at(__builtin_addressof(__p[__i]));
107	return __p;
108	}
109	};
110
111	template<typename _Dummy_for_PR85282>
112	struct _Alloc_traits_impl<char_traits<_CharT>, _Dummy_for_PR85282>
113	: __gnu_cxx::__alloc_traits<_Char_alloc_type>
114	{
115	// std::char_traits begins the lifetime of characters.
116	};
117
118	using _Alloc_traits = _Alloc_traits_impl<_Traits, void>;
119	#endif
120
121	// Types:
122	public:
123	typedef _Traits traits_type;
124	typedef typename _Traits::char_type value_type;
125	typedef _Char_alloc_type allocator_type;
126	typedef typename _Alloc_traits::size_type size_type;
127	typedef typename _Alloc_traits::difference_type difference_type;
128	typedef typename _Alloc_traits::reference reference;
129	typedef typename _Alloc_traits::const_reference const_reference;
130	typedef typename _Alloc_traits::pointer pointer;
131	typedef typename _Alloc_traits::const_pointer const_pointer;
132	typedef __gnu_cxx::__normal_iterator<pointer, basic_string> iterator;
133	typedef __gnu_cxx::__normal_iterator<const_pointer, basic_string>
134	const_iterator;
135	typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
136	typedef std::reverse_iterator<iterator> reverse_iterator;
137
138	/// Value returned by various member functions when they fail.
139	static const size_type npos = static_cast<size_type>(-`1`);
140
141	protected:
142	// type used for positions in insert, erase etc.
143	#if __cplusplus < 201103L
144	typedef iterator __const_iterator;
145	#else
146	typedef const_iterator __const_iterator;
147	#endif
148
149	private:
150	#if __cplusplus >= 201703L
151	// A helper type for avoiding boiler-plate.
152	typedef basic_string_view<_CharT, _Traits> __sv_type;
153
154	template<typename _Tp, typename _Res>
155	using _If_sv = enable_if_t<
156	__and_<is_convertible<const _Tp&, __sv_type>,
157	__not_<is_convertible<const _Tp, const* basic_string*>>,
158	__not_<is_convertible<const _Tp&, const _CharT*>>>::value,
159	_Res>;
160
161	// Allows an implicit conversion to __sv_type.
162	_GLIBCXX20_CONSTEXPR
163	static __sv_type
164	_S_to_string_view(__sv_type __svt) noexcept
165	{ return __svt; }
166
167	// Wraps a string_view by explicit conversion and thus
168	// allows to add an internal constructor that does not
169	// participate in overload resolution when a string_view
170	// is provided.
171	struct __sv_wrapper
172	{
173	_GLIBCXX20_CONSTEXPR explicit
174	__sv_wrapper(__sv_type __sv) noexcept : _M_sv(__sv) { }
175
176	__sv_type _M_sv;
177	};
178
179	/**
180	* @brief Only internally used: Construct string from a string view
181	* wrapper.
182	* @param __svw string view wrapper.
183	* @param __a Allocator to use.
184	*/
185	_GLIBCXX20_CONSTEXPR
186	explicit
187	basic_string(__sv_wrapper __svw, const _Alloc& __a)
188	: basic_string(__svw._M_sv.data(), __svw._M_sv.size(), __a) { }
189	#endif
190
191	// Use empty-base optimization: http://www.cantrip.org/emptyopt.html
192	struct _Alloc_hider : allocator_type // TODO check __is_final
193	{
194	#if __cplusplus < 201103L
195	_Alloc_hider(pointer __dat, const _Alloc& __a = _Alloc())
196	: allocator_type(__a), _M_p(__dat) { }
197	#else
198	_GLIBCXX20_CONSTEXPR
199	_Alloc_hider(pointer __dat, const _Alloc& __a)
200	: allocator_type(__a), _M_p(__dat) { }
201
202	_GLIBCXX20_CONSTEXPR
203	_Alloc_hider(pointer __dat, _Alloc&& __a = _Alloc())
204	: allocator_type(std::move(__a)), _M_p(__dat) { }
205	#endif
206
207	pointer _M_p; // The actual data.
208	};
209
210	_Alloc_hider _M_dataplus;
211	size_type _M_string_length;
212
213	enum { _S_local_capacity = `15` / sizeof(_CharT) };
214
215	union
216	{
217	_CharT _M_local_buf[_S_local_capacity + `1`];
218	size_type _M_allocated_capacity;
219	};
220
221	_GLIBCXX20_CONSTEXPR
222	void
223	_M_data(pointer __p)
224	{ _M_dataplus._M_p = __p; }
225
226	_GLIBCXX20_CONSTEXPR
227	void
228	_M_length(size_type __length)
229	{ _M_string_length = __length; }
230
231	_GLIBCXX20_CONSTEXPR
232	pointer
233	_M_data() const
234	{ return _M_dataplus._M_p; }
235
236	_GLIBCXX20_CONSTEXPR
237	pointer
238	_M_local_data()
239	{
240	#if __cplusplus >= 201103L
241	return std::pointer_traits<pointer>::pointer_to(*_M_local_buf);
242	#else
243	return pointer(_M_local_buf);
244	#endif
245	}
246
247	_GLIBCXX20_CONSTEXPR
248	const_pointer
249	_M_local_data() const
250	{
251	#if __cplusplus >= 201103L
252	return std::pointer_traits<const_pointer>::pointer_to(*_M_local_buf);
253	#else
254	return const_pointer(_M_local_buf);
255	#endif
256	}
257
258	_GLIBCXX20_CONSTEXPR
259	void
260	_M_capacity(size_type __capacity)
261	{ _M_allocated_capacity = __capacity; }
262
263	_GLIBCXX20_CONSTEXPR
264	void
265	_M_set_length(size_type __n)
266	{
267	_M_length(__n);
268	traits_type::assign(_M_data()[__n], _CharT());
269	}
270
271	_GLIBCXX20_CONSTEXPR
272	bool
273	_M_is_local() const
274	{
275	if (_M_data() == _M_local_data())
276	{
277	if (_M_string_length > _S_local_capacity)
278	__builtin_unreachable();
279	return true;
280	}
281	return false;
282	}
283
284	// Create & Destroy
285	_GLIBCXX20_CONSTEXPR
286	pointer
287	_M_create(size_type&, size_type);
288
289	_GLIBCXX20_CONSTEXPR
290	void
291	_M_dispose()
292	{
293	if (!_M_is_local())
294	_M_destroy(_M_allocated_capacity);
295	}
296
297	_GLIBCXX20_CONSTEXPR
298	void
299	_M_destroy(size_type __size) throw()
300	{ _Alloc_traits::deallocate(_M_get_allocator(), _M_data(), __size + `1`); }
301
302	#if __cplusplus < 201103L \|\| defined _GLIBCXX_DEFINING_STRING_INSTANTIATIONS
303	// _M_construct_aux is used to implement the 21.3.1 para 15 which
304	// requires special behaviour if _InIterator is an integral type
305	template<typename _InIterator>
306	void
307	_M_construct_aux(_InIterator __beg, _InIterator __end,
308	std::__false_type)
309	{
310	typedef typename iterator_traits<_InIterator>::iterator_category _Tag;
311	_M_construct(__beg, __end, _Tag());
312	}
313
314	// _GLIBCXX_RESOLVE_LIB_DEFECTS
315	// 438. Ambiguity in the "do the right thing" clause
316	template<typename _Integer>
317	void
318	_M_construct_aux(_Integer __beg, _Integer __end, std::__true_type)
319	{ _M_construct_aux_2(static_cast<size_type>(__beg), __end); }
320
321	void
322	_M_construct_aux_2(size_type __req, _CharT __c)
323	{ _M_construct(__req, __c); }
324	#endif
325
326	// For Input Iterators, used in istreambuf_iterators, etc.
327	template<typename _InIterator>
328	_GLIBCXX20_CONSTEXPR
329	void
330	_M_construct(_InIterator __beg, _InIterator __end,
331	std::input_iterator_tag);
332
333	// For forward_iterators up to random_access_iterators, used for
334	// string::iterator, _CharT, etc.*
335	template<typename _FwdIterator>
336	_GLIBCXX20_CONSTEXPR
337	void
338	_M_construct(_FwdIterator __beg, _FwdIterator __end,
339	std::forward_iterator_tag);
340
341	_GLIBCXX20_CONSTEXPR
342	void
343	_M_construct(size_type __req, _CharT __c);
344
345	_GLIBCXX20_CONSTEXPR
346	allocator_type&
347	_M_get_allocator()
348	{ return _M_dataplus; }
349
350	_GLIBCXX20_CONSTEXPR
351	const allocator_type&
352	_M_get_allocator() const
353	{ return _M_dataplus; }
354
355	// Ensure that _M_local_buf is the active member of the union.
356	__attribute__((__always_inline__))
357	_GLIBCXX14_CONSTEXPR
358	pointer
359	_M_use_local_data() _GLIBCXX_NOEXCEPT
360	{
361	#if __cpp_lib_is_constant_evaluated
362	if (std::is_constant_evaluated())
363	for (size_type __i = `0`; __i <= _S_local_capacity; ++__i)
364	_M_local_buf[__i] = _CharT();
365	#endif
366	return _M_local_data();
367	}
368
369	private:
370
371	#ifdef _GLIBCXX_DISAMBIGUATE_REPLACE_INST
372	// The explicit instantiations in misc-inst.cc require this due to
373	// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64063
374	template<typename _Tp, bool _Requires =
375	!__are_same<_Tp, _CharT*>::__value
376	&& !__are_same<_Tp, const _CharT*>::__value
377	&& !__are_same<_Tp, iterator>::__value
378	&& !__are_same<_Tp, const_iterator>::__value>
379	struct __enable_if_not_native_iterator
380	{ typedef basic_string& __type; };
381	template<typename _Tp>
382	struct __enable_if_not_native_iterator<_Tp, false> { };
383	#endif
384
385	_GLIBCXX20_CONSTEXPR
386	size_type
387	_M_check(size_type __pos, const char* __s) const
388	{
389	if (__pos > this->size())
390	__throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > "
391	"this->size() (which is %zu)"),
392	__s, __pos, this->size());
393	return __pos;
394	}
395
396	_GLIBCXX20_CONSTEXPR
397	void
398	_M_check_length(size_type __n1, size_type __n2, const char* __s) const
399	{
400	if (this->max_size() - (this->size() - __n1) < __n2)
401	__throw_length_error(__N(__s));
402	}
403
404
405	// NB: _M_limit doesn't check for a bad __pos value.
406	_GLIBCXX20_CONSTEXPR
407	size_type
408	_M_limit(size_type __pos, size_type __off) const _GLIBCXX_NOEXCEPT
409	{
410	const bool __testoff = __off < this->size() - __pos;
411	return __testoff ? __off : this->size() - __pos;
412	}
413
414	// True if _Rep and source do not overlap.
415	bool
416	_M_disjunct(const _CharT* __s) const _GLIBCXX_NOEXCEPT
417	{
418	return (less<const _CharT*>()(__s, _M_data())
419	\|\| less<const _CharT>()(_M_data() + this*->size(), __s));
420	}
421
422	// When __n = 1 way faster than the general multichar
423	// traits_type::copy/move/assign.
424	_GLIBCXX20_CONSTEXPR
425	static void
426	_S_copy(_CharT* __d, const _CharT* __s, size_type __n)
427	{
428	if (__n == `1`)
429	traits_type::assign(__d, __s);
430	else
431	traits_type::copy(__d, __s, __n);
432	}
433
434	_GLIBCXX20_CONSTEXPR
435	static void
436	_S_move(_CharT* __d, const _CharT* __s, size_type __n)
437	{
438	if (__n == `1`)
439	traits_type::assign(__d, __s);
440	else
441	traits_type::move(__d, __s, __n);
442	}
443
444	_GLIBCXX20_CONSTEXPR
445	static void
446	_S_assign(_CharT* __d, size_type __n, _CharT __c)
447	{
448	if (__n == `1`)
449	traits_type::assign(*__d, __c);
450	else
451	traits_type::assign(__d, __n, __c);
452	}
453
454	// _S_copy_chars is a separate template to permit specialization
455	// to optimize for the common case of pointers as iterators.
456	template<class _Iterator>
457	_GLIBCXX20_CONSTEXPR
458	static void
459	_S_copy_chars(_CharT* __p, _Iterator __k1, _Iterator __k2)
460	{
461	for (; __k1 != __k2; ++__k1, (void)++__p)
462	traits_type::assign(__p, __k1); // These types are off.
463	}
464
465	_GLIBCXX20_CONSTEXPR
466	static void
467	_S_copy_chars(_CharT* __p, iterator __k1, iterator __k2) _GLIBCXX_NOEXCEPT
468	{ _S_copy_chars(__p, __k1.base(), __k2.base()); }
469
470	_GLIBCXX20_CONSTEXPR
471	static void
472	_S_copy_chars(_CharT* __p, const_iterator __k1, const_iterator __k2)
473	_GLIBCXX_NOEXCEPT
474	{ _S_copy_chars(__p, __k1.base(), __k2.base()); }
475
476	_GLIBCXX20_CONSTEXPR
477	static void
478	_S_copy_chars(_CharT* __p, _CharT* __k1, _CharT* __k2) _GLIBCXX_NOEXCEPT
479	{ _S_copy(__p, __k1, __k2 - __k1); }
480
481	_GLIBCXX20_CONSTEXPR
482	static void
483	_S_copy_chars(_CharT* __p, const _CharT* __k1, const _CharT* __k2)
484	_GLIBCXX_NOEXCEPT
485	{ _S_copy(__p, __k1, __k2 - __k1); }
486
487	_GLIBCXX20_CONSTEXPR
488	static int
489	_S_compare(size_type __n1, size_type __n2) _GLIBCXX_NOEXCEPT
490	{
491	const difference_type __d = difference_type(__n1 - __n2);
492
493	if (__d > __gnu_cxx::__numeric_traits<int>::__max)
494	return __gnu_cxx::__numeric_traits<int>::__max;
495	else if (__d < __gnu_cxx::__numeric_traits<int>::__min)
496	return __gnu_cxx::__numeric_traits<int>::__min;
497	else
498	return int(__d);
499	}
500
501	_GLIBCXX20_CONSTEXPR
502	void
503	_M_assign(const basic_string&);
504
505	_GLIBCXX20_CONSTEXPR
506	void
507	_M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
508	size_type __len2);
509
510	_GLIBCXX20_CONSTEXPR
511	void
512	_M_erase(size_type __pos, size_type __n);
513
514	public:
515	// Construct/copy/destroy:
516	// NB: We overload ctors in some cases instead of using default
517	// arguments, per 17.4.4.4 para. 2 item 2.
518
519	/**
520	* @brief Default constructor creates an empty string.
521	*/
522	_GLIBCXX20_CONSTEXPR
523	basic_string()
524	_GLIBCXX_NOEXCEPT_IF(is_nothrow_default_constructible<_Alloc>::value)
525	: _M_dataplus(_M_local_data())
526	{
527	_M_use_local_data();
528	_M_set_length(`0`);
529	}
530
531	/**
532	* @brief Construct an empty string using allocator @a a.
533	*/
534	_GLIBCXX20_CONSTEXPR
535	explicit
536	basic_string(const _Alloc& __a) _GLIBCXX_NOEXCEPT
537	: _M_dataplus(_M_local_data(), __a)
538	{
539	_M_use_local_data();
540	_M_set_length(`0`);
541	}
542
543	/**
544	* @brief Construct string with copy of value of @a __str.
545	* @param __str Source string.
546	*/
547	_GLIBCXX20_CONSTEXPR
548	basic_string(const basic_string& __str)
549	: _M_dataplus(_M_local_data(),
550	_Alloc_traits::_S_select_on_copy(__str._M_get_allocator()))
551	{
552	_M_construct(__str._M_data(), __str._M_data() + __str.length(),
553	std::forward_iterator_tag ());
554	}
555
556	// _GLIBCXX_RESOLVE_LIB_DEFECTS
557	// 2583. no way to supply an allocator for basic_string(str, pos)
558	/**
559	* @brief Construct string as copy of a substring.
560	* @param __str Source string.
561	* @param __pos Index of first character to copy from.
562	* @param __a Allocator to use.
563	*/
564	_GLIBCXX20_CONSTEXPR
565	basic_string(const basic_string& __str, size_type __pos,
566	const _Alloc& __a = _Alloc())
567	: _M_dataplus(_M_local_data(), __a)
568	{
569	const _CharT* __start = __str._M_data()
570	+ __str._M_check(__pos, "basic_string::basic_string");
571	_M_construct(__start, __start + __str._M_limit(__pos, npos),
572	std::forward_iterator_tag ());
573	}
574
575	/**
576	* @brief Construct string as copy of a substring.
577	* @param __str Source string.
578	* @param __pos Index of first character to copy from.
579	* @param __n Number of characters to copy.
580	*/
581	_GLIBCXX20_CONSTEXPR
582	basic_string(const basic_string& __str, size_type __pos,
583	size_type __n)
584	: _M_dataplus(_M_local_data())
585	{
586	const _CharT* __start = __str._M_data()
587	+ __str._M_check(__pos, "basic_string::basic_string");
588	_M_construct(__start, __start + __str._M_limit(__pos, __n),
589	std::forward_iterator_tag ());
590	}
591
592	/**
593	* @brief Construct string as copy of a substring.
594	* @param __str Source string.
595	* @param __pos Index of first character to copy from.
596	* @param __n Number of characters to copy.
597	* @param __a Allocator to use.
598	*/
599	_GLIBCXX20_CONSTEXPR
600	basic_string(const basic_string& __str, size_type __pos,
601	size_type __n, const _Alloc& __a)
602	: _M_dataplus(_M_local_data(), __a)
603	{
604	const _CharT* __start
605	= __str._M_data() + __str._M_check(__pos, "string::string");
606	_M_construct(__start, __start + __str._M_limit(__pos, __n),
607	std::forward_iterator_tag ());
608	}
609
610	/**
611	* @brief Construct string initialized by a character %array.
612	* @param __s Source character %array.
613	* @param __n Number of characters to copy.
614	* @param __a Allocator to use (default is default allocator).
615	*
616	* NB: @a __s must have at least @a __n characters, '\\0'
617	* has no special meaning.
618	*/
619	_GLIBCXX20_CONSTEXPR
620	basic_string(const _CharT* __s, size_type __n,
621	const _Alloc& __a = _Alloc())
622	: _M_dataplus(_M_local_data(), __a)
623	{
624	// NB: Not required, but considered best practice.
625	if (__s == `0` && __n > `0`)
626	std::__throw_logic_error(__N("basic_string: "
627	"construction from null is not valid"));
628	_M_construct(__s, __s + __n, std::forward_iterator_tag ());
629	}
630
631	/**
632	* @brief Construct string as copy of a C string.
633	* @param __s Source C string.
634	* @param __a Allocator to use (default is default allocator).
635	*/
636	#if __cpp_deduction_guides && ! defined _GLIBCXX_DEFINING_STRING_INSTANTIATIONS
637	// _GLIBCXX_RESOLVE_LIB_DEFECTS
638	// 3076. basic_string CTAD ambiguity
639	template<typename = _RequireAllocator<_Alloc>>
640	#endif
641	_GLIBCXX20_CONSTEXPR
642	basic_string(const _CharT* __s, const _Alloc& __a = _Alloc())
643	: _M_dataplus(_M_local_data(), __a)
644	{
645	// NB: Not required, but considered best practice.
646	if (__s == `0`)
647	std::__throw_logic_error(__N("basic_string: "
648	"construction from null is not valid"));
649	const _CharT* __end = __s + traits_type::length(__s);
650	_M_construct(__s, __end, forward_iterator_tag ());
651	}
652
653	/**
654	* @brief Construct string as multiple characters.
655	* @param __n Number of characters.
656	* @param __c Character to use.
657	* @param __a Allocator to use (default is default allocator).
658	*/
659	#if __cpp_deduction_guides && ! defined _GLIBCXX_DEFINING_STRING_INSTANTIATIONS
660	// _GLIBCXX_RESOLVE_LIB_DEFECTS
661	// 3076. basic_string CTAD ambiguity
662	template<typename = _RequireAllocator<_Alloc>>
663	#endif
664	_GLIBCXX20_CONSTEXPR
665	basic_string(size_type __n, _CharT __c, const _Alloc& __a = _Alloc())
666	: _M_dataplus(_M_local_data(), __a)
667	{ _M_construct(__n, __c); }
668
669	#if __cplusplus >= 201103L
670	/**
671	* @brief Move construct string.
672	* @param __str Source string.
673	*
674	* The newly-created string contains the exact contents of @a __str.
675	* @a __str is a valid, but unspecified string.
676	*/
677	_GLIBCXX20_CONSTEXPR
678	basic_string(basic_string&& __str) noexcept
679	: _M_dataplus(_M_local_data(), std::move(__str._M_get_allocator()))
680	{
681	if (__str._M_is_local())
682	{
683	traits_type::copy(_M_local_buf, __str._M_local_buf,
684	__str.length() + `1`);
685	}
686	else
687	{
688	_M_data(__str._M_data());
689	_M_capacity(__str._M_allocated_capacity);
690	}
691
692	// Must use _M_length() here not _M_set_length() because
693	// basic_stringbuf relies on writing into unallocated capacity so
694	// we mess up the contents if we put a '\0' in the string.
695	_M_length(__str.length());
696	__str._M_data(__str._M_local_data());
697	__str._M_set_length(`0`);
698	}
699
700	/**
701	* @brief Construct string from an initializer %list.
702	* @param __l std::initializer_list of characters.
703	* @param __a Allocator to use (default is default allocator).
704	*/
705	_GLIBCXX20_CONSTEXPR
706	basic_string(initializer_list<_CharT> __l, const _Alloc& __a = _Alloc())
707	: _M_dataplus(_M_local_data(), __a)
708	{ _M_construct(__l.begin(), __l.end(), std::forward_iterator_tag ()); }
709
710	_GLIBCXX20_CONSTEXPR
711	basic_string(const basic_string& __str, const _Alloc& __a)
712	: _M_dataplus(_M_local_data(), __a)
713	{ _M_construct(__str.begin(), __str.end(), std::forward_iterator_tag ()); }
714
715	_GLIBCXX20_CONSTEXPR
716	basic_string(basic_string&& __str, const _Alloc& __a)
717	noexcept(_Alloc_traits::_S_always_equal())
718	: _M_dataplus(_M_local_data(), __a)
719	{
720	if (__str._M_is_local())
721	{
722	traits_type::copy(_M_local_buf, __str._M_local_buf,
723	__str.length() + `1`);
724	_M_length(__str.length());
725	__str._M_set_length(`0`);
726	}
727	else if (_Alloc_traits::_S_always_equal()
728	\|\| __str.get_allocator() == __a)
729	{
730	_M_data(__str._M_data());
731	_M_length(__str.length());
732	_M_capacity(__str._M_allocated_capacity);
733	__str._M_data(__str._M_local_buf);
734	__str._M_set_length(`0`);
735	}
736	else
737	_M_construct(__str.begin(), __str.end(), std::forward_iterator_tag ());
738	}
739	#endif // C++11
740
741	#if __cplusplus >= 202100L
742	basic_string(nullptr_t) = delete;
743	basic_string& operator=(nullptr_t) = delete;
744	#endif // C++23
745
746	/**
747	* @brief Construct string as copy of a range.
748	* @param __beg Start of range.
749	* @param __end End of range.
750	* @param __a Allocator to use (default is default allocator).
751	*/
752	#if __cplusplus >= 201103L
753	template<typename _InputIterator,
754	typename = std::_RequireInputIter<_InputIterator>>
755	#else
756	template<typename _InputIterator>
757	#endif
758	_GLIBCXX20_CONSTEXPR
759	basic_string(_InputIterator __beg, _InputIterator __end,
760	const _Alloc& __a = _Alloc())
761	: _M_dataplus(_M_local_data(), __a), _M_string_length(`0`)
762	{
763	#if __cplusplus >= 201103L
764	_M_construct(__beg, __end, std::__iterator_category(__beg));
765	#else
766	typedef typename std::__is_integer<_InputIterator>::__type _Integral;
767	_M_construct_aux(__beg, __end, _Integral());
768	#endif
769	}
770
771	#if __cplusplus >= 201703L
772	/**
773	* @brief Construct string from a substring of a string_view.
774	* @param __t Source object convertible to string view.
775	* @param __pos The index of the first character to copy from __t.
776	* @param __n The number of characters to copy from __t.
777	* @param __a Allocator to use.
778	*/
779	template<typename _Tp,
780	typename = enable_if_t<is_convertible_v<const _Tp&, __sv_type>>>
781	_GLIBCXX20_CONSTEXPR
782	basic_string(const _Tp& __t, size_type __pos, size_type __n,
783	const _Alloc& __a = _Alloc())
784	: basic_string(_S_to_string_view(__t).substr(__pos, __n), __a) { }
785
786	/**
787	* @brief Construct string from a string_view.
788	* @param __t Source object convertible to string view.
789	* @param __a Allocator to use (default is default allocator).
790	*/
791	template<typename _Tp, typename = _If_sv<_Tp, void>>
792	_GLIBCXX20_CONSTEXPR
793	explicit
794	basic_string(const _Tp& __t, const _Alloc& __a = _Alloc())
795	: basic_string(__sv_wrapper(_S_to_string_view(__t)), __a) { }
796	#endif // C++17
797
798	/**
799	* @brief Destroy the string instance.
800	*/
801	_GLIBCXX20_CONSTEXPR
802	~basic_string()
803	{ _M_dispose(); }
804
805	/**
806	* @brief Assign the value of @a str to this string.
807	* @param __str Source string.
808	*/
809	_GLIBCXX20_CONSTEXPR
810	basic_string&
811	operator=(const basic_string& __str)
812	{
813	return this->assign(__str);
814	}
815
816	/**
817	* @brief Copy contents of @a s into this string.
818	* @param __s Source null-terminated string.
819	*/
820	_GLIBCXX20_CONSTEXPR
821	basic_string&
822	operator=(const _CharT* __s)
823	{ return this->assign(__s); }
824
825	/**
826	* @brief Set value to string of length 1.
827	* @param __c Source character.
828	*
829	* Assigning to a character makes this string length 1 and
830	* (*this)[0] == @a c.
831	*/
832	_GLIBCXX20_CONSTEXPR
833	basic_string&
834	operator=(_CharT __c)
835	{
836	this->assign(`1`, __c);
837	return *this;
838	}
839
840	#if __cplusplus >= 201103L
841	/**
842	* @brief Move assign the value of @a str to this string.
843	* @param __str Source string.
844	*
845	* The contents of @a str are moved into this string (without copying).
846	* @a str is a valid, but unspecified string.
847	*/
848	// _GLIBCXX_RESOLVE_LIB_DEFECTS
849	// 2063. Contradictory requirements for string move assignment
850	_GLIBCXX20_CONSTEXPR
851	basic_string&
852	operator=(basic_string&& __str)
853	noexcept(_Alloc_traits::_S_nothrow_move())
854	{
855	if (!_M_is_local() && _Alloc_traits::_S_propagate_on_move_assign()
856	&& !_Alloc_traits::_S_always_equal()
857	&& _M_get_allocator() != __str._M_get_allocator())
858	{
859	// Destroy existing storage before replacing allocator.
860	_M_destroy(_M_allocated_capacity);
861	_M_data(_M_local_data());
862	_M_set_length(`0`);
863	}
864	// Replace allocator if POCMA is true.
865	std::__alloc_on_move(_M_get_allocator(), __str._M_get_allocator());
866
867	if (__str._M_is_local())
868	{
869	// We've always got room for a short string, just copy it
870	// (unless this is a self-move, because that would violate the
871	// char_traits::copy precondition that the ranges don't overlap).
872	if (__builtin_expect(std::__addressof(__str) != this, true))
873	{
874	if (__str.size())
875	this->_S_copy(_M_data(), __str._M_data(), __str.size());
876	_M_set_length(__str.size());
877	}
878	}
879	else if (_Alloc_traits::_S_propagate_on_move_assign()
880	\|\| _Alloc_traits::_S_always_equal()
881	\|\| _M_get_allocator() == __str._M_get_allocator())
882	{
883	// Just move the allocated pointer, our allocator can free it.
884	pointer __data = nullptr;
885	size_type __capacity;
886	if (!_M_is_local())
887	{
888	if (_Alloc_traits::_S_always_equal())
889	{
890	// __str can reuse our existing storage.
891	__data = _M_data();
892	__capacity = _M_allocated_capacity;
893	}
894	else // __str can't use it, so free it.
895	_M_destroy(_M_allocated_capacity);
896	}
897
898	_M_data(__str._M_data());
899	_M_length(__str.length());
900	_M_capacity(__str._M_allocated_capacity);
901	if (__data)
902	{
903	__str._M_data(__data);
904	__str._M_capacity(__capacity);
905	}
906	else
907	__str._M_data(__str._M_local_buf);
908	}
909	else // Need to do a deep copy
910	assign(__str);
911	__str.clear();
912	return *this;
913	}
914
915	/**
916	* @brief Set value to string constructed from initializer %list.
917	* @param __l std::initializer_list.
918	*/
919	_GLIBCXX20_CONSTEXPR
920	basic_string&
921	operator=(initializer_list<_CharT> __l)
922	{
923	this->assign(__l.begin(), __l.size());
924	return *this;
925	}
926	#endif // C++11
927
928	#if __cplusplus >= 201703L
929	/**
930	* @brief Set value to string constructed from a string_view.
931	* @param __svt An object convertible to string_view.
932	*/
933	template<typename _Tp>
934	_GLIBCXX20_CONSTEXPR
935	_If_sv<_Tp, basic_string&>
936	operator=(const _Tp& __svt)
937	{ return this->assign(__svt); }
938
939	/**
940	* @brief Convert to a string_view.
941	* @return A string_view.
942	*/
943	_GLIBCXX20_CONSTEXPR
944	operator __sv_type() const noexcept
945	{ return __sv_type(data(), size()); }
946	#endif // C++17
947
948	// Iterators:
949	/**
950	* Returns a read/write iterator that points to the first character in
951	* the %string.
952	*/
953	_GLIBCXX20_CONSTEXPR
954	iterator
955	begin() _GLIBCXX_NOEXCEPT
956	{ return iterator(_M_data()); }
957
958	/**
959	* Returns a read-only (constant) iterator that points to the first
960	* character in the %string.
961	*/
962	_GLIBCXX20_CONSTEXPR
963	const_iterator
964	begin() const _GLIBCXX_NOEXCEPT
965	{ return const_iterator(_M_data()); }
966
967	/**
968	* Returns a read/write iterator that points one past the last
969	* character in the %string.
970	*/
971	_GLIBCXX20_CONSTEXPR
972	iterator
973	end() _GLIBCXX_NOEXCEPT
974	{ return iterator(_M_data() + this->size()); }
975
976	/**
977	* Returns a read-only (constant) iterator that points one past the
978	* last character in the %string.
979	*/
980	_GLIBCXX20_CONSTEXPR
981	const_iterator
982	end() const _GLIBCXX_NOEXCEPT
983	{ return const_iterator(_M_data() + this->size()); }
984
985	/**
986	* Returns a read/write reverse iterator that points to the last
987	* character in the %string. Iteration is done in reverse element
988	* order.
989	*/
990	_GLIBCXX20_CONSTEXPR
991	reverse_iterator
992	rbegin() _GLIBCXX_NOEXCEPT
993	{ return reverse_iterator(this->end()); }
994
995	/**
996	* Returns a read-only (constant) reverse iterator that points
997	* to the last character in the %string. Iteration is done in
998	* reverse element order.
999	*/
1000	_GLIBCXX20_CONSTEXPR
1001	const_reverse_iterator
1002	rbegin() const _GLIBCXX_NOEXCEPT
1003	{ return const_reverse_iterator(this->end()); }
1004
1005	/**
1006	* Returns a read/write reverse iterator that points to one before the
1007	* first character in the %string. Iteration is done in reverse
1008	* element order.
1009	*/
1010	_GLIBCXX20_CONSTEXPR
1011	reverse_iterator
1012	rend() _GLIBCXX_NOEXCEPT
1013	{ return reverse_iterator(this->begin()); }
1014
1015	/**
1016	* Returns a read-only (constant) reverse iterator that points
1017	* to one before the first character in the %string. Iteration
1018	* is done in reverse element order.
1019	*/
1020	_GLIBCXX20_CONSTEXPR
1021	const_reverse_iterator
1022	rend() const _GLIBCXX_NOEXCEPT
1023	{ return const_reverse_iterator(this->begin()); }
1024
1025	#if __cplusplus >= 201103L
1026	/**
1027	* Returns a read-only (constant) iterator that points to the first
1028	* character in the %string.
1029	*/
1030	_GLIBCXX20_CONSTEXPR
1031	const_iterator
1032	cbegin() const noexcept
1033	{ return const_iterator(this->_M_data()); }
1034
1035	/**
1036	* Returns a read-only (constant) iterator that points one past the
1037	* last character in the %string.
1038	*/
1039	_GLIBCXX20_CONSTEXPR
1040	const_iterator
1041	cend() const noexcept
1042	{ return const_iterator(this->_M_data() + this->size()); }
1043
1044	/**
1045	* Returns a read-only (constant) reverse iterator that points
1046	* to the last character in the %string. Iteration is done in
1047	* reverse element order.
1048	*/
1049	_GLIBCXX20_CONSTEXPR
1050	const_reverse_iterator
1051	crbegin() const noexcept
1052	{ return const_reverse_iterator(this->end()); }
1053
1054	/**
1055	* Returns a read-only (constant) reverse iterator that points
1056	* to one before the first character in the %string. Iteration
1057	* is done in reverse element order.
1058	*/
1059	_GLIBCXX20_CONSTEXPR
1060	const_reverse_iterator
1061	crend() const noexcept
1062	{ return const_reverse_iterator(this->begin()); }
1063	#endif
1064
1065	public:
1066	// Capacity:
1067	/// Returns the number of characters in the string, not including any
1068	/// null-termination.
1069	_GLIBCXX20_CONSTEXPR
1070	size_type
1071	size() const _GLIBCXX_NOEXCEPT
1072	{ return _M_string_length; }
1073
1074	/// Returns the number of characters in the string, not including any
1075	/// null-termination.
1076	_GLIBCXX20_CONSTEXPR
1077	size_type
1078	length() const _GLIBCXX_NOEXCEPT
1079	{ return _M_string_length; }
1080
1081	/// Returns the size() of the largest possible %string.
1082	_GLIBCXX20_CONSTEXPR
1083	size_type
1084	max_size() const _GLIBCXX_NOEXCEPT
1085	{ return (_Alloc_traits::max_size(_M_get_allocator()) - `1`) / `2`; }
1086
1087	/**
1088	* @brief Resizes the %string to the specified number of characters.
1089	* @param __n Number of characters the %string should contain.
1090	* @param __c Character to fill any new elements.
1091	*
1092	* This function will %resize the %string to the specified
1093	* number of characters. If the number is smaller than the
1094	* %string's current size the %string is truncated, otherwise
1095	* the %string is extended and new elements are %set to @a __c.
1096	*/
1097	_GLIBCXX20_CONSTEXPR
1098	void
1099	resize(size_type __n, _CharT __c);
1100
1101	/**
1102	* @brief Resizes the %string to the specified number of characters.
1103	* @param __n Number of characters the %string should contain.
1104	*
1105	* This function will resize the %string to the specified length. If
1106	* the new size is smaller than the %string's current size the %string
1107	* is truncated, otherwise the %string is extended and new characters
1108	* are default-constructed. For basic types such as char, this means
1109	* setting them to 0.
1110	*/
1111	_GLIBCXX20_CONSTEXPR
1112	void
1113	resize(size_type __n)
1114	{ this->resize(__n, _CharT()); }
1115
1116	#if __cplusplus >= 201103L
1117	#pragma GCC diagnostic push
1118	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1119	/// A non-binding request to reduce capacity() to size().
1120	_GLIBCXX20_CONSTEXPR
1121	void
1122	shrink_to_fit() noexcept
1123	{ reserve(); }
1124	#pragma GCC diagnostic pop
1125	#endif
1126
1127	#if __cplusplus > 202002L
1128	#define __cpp_lib_string_resize_and_overwrite 202110L
1129	template<typename _Operation>
1130	constexpr void
1131	resize_and_overwrite(size_type __n, _Operation __op);
1132	#endif
1133
1134	/**
1135	* Returns the total number of characters that the %string can hold
1136	* before needing to allocate more memory.
1137	*/
1138	_GLIBCXX20_CONSTEXPR
1139	size_type
1140	capacity() const _GLIBCXX_NOEXCEPT
1141	{
1142	return _M_is_local() ? size_type(_S_local_capacity)
1143	: _M_allocated_capacity;
1144	}
1145
1146	/**
1147	* @brief Attempt to preallocate enough memory for specified number of
1148	* characters.
1149	* @param __res_arg Number of characters required.
1150	* @throw std::length_error If @a __res_arg exceeds @c max_size().
1151	*
1152	* This function attempts to reserve enough memory for the
1153	* %string to hold the specified number of characters. If the
1154	* number requested is more than max_size(), length_error is
1155	* thrown.
1156	*
1157	* The advantage of this function is that if optimal code is a
1158	* necessity and the user can determine the string length that will be
1159	* required, the user can reserve the memory in %advance, and thus
1160	* prevent a possible reallocation of memory and copying of %string
1161	* data.
1162	*/
1163	_GLIBCXX20_CONSTEXPR
1164	void
1165	reserve(size_type __res_arg);
1166
1167	/**
1168	* Equivalent to shrink_to_fit().
1169	*/
1170	#if __cplusplus > 201703L
1171	[[deprecated("use shrink_to_fit() instead")]]
1172	#endif
1173	_GLIBCXX20_CONSTEXPR
1174	void
1175	reserve();
1176
1177	/**
1178	* Erases the string, making it empty.
1179	*/
1180	_GLIBCXX20_CONSTEXPR
1181	void
1182	clear() _GLIBCXX_NOEXCEPT
1183	{ _M_set_length(`0`); }
1184
1185	/**
1186	* Returns true if the %string is empty. Equivalent to
1187	* <code>*this == ""</code>.
1188	*/
1189	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1190	bool
1191	empty() const _GLIBCXX_NOEXCEPT
1192	{ return this->size() == `0`; }
1193
1194	// Element access:
1195	/**
1196	* @brief Subscript access to the data contained in the %string.
1197	* @param __pos The index of the character to access.
1198	* @return Read-only (constant) reference to the character.
1199	*
1200	* This operator allows for easy, array-style, data access.
1201	* Note that data access with this operator is unchecked and
1202	* out_of_range lookups are not defined. (For checked lookups
1203	* see at().)
1204	*/
1205	_GLIBCXX20_CONSTEXPR
1206	const_reference
1207	operator[] (size_type __pos) const _GLIBCXX_NOEXCEPT
1208	{
1209	__glibcxx_assert(__pos <= size());
1210	return _M_data()[__pos];
1211	}
1212
1213	/**
1214	* @brief Subscript access to the data contained in the %string.
1215	* @param __pos The index of the character to access.
1216	* @return Read/write reference to the character.
1217	*
1218	* This operator allows for easy, array-style, data access.
1219	* Note that data access with this operator is unchecked and
1220	* out_of_range lookups are not defined. (For checked lookups
1221	* see at().)
1222	*/
1223	_GLIBCXX20_CONSTEXPR
1224	reference
1225	operator[](size_type __pos)
1226	{
1227	// Allow pos == size() both in C++98 mode, as v3 extension,
1228	// and in C++11 mode.
1229	__glibcxx_assert(__pos <= size());
1230	// In pedantic mode be strict in C++98 mode.
1231	_GLIBCXX_DEBUG_PEDASSERT(__cplusplus >= `201103L` \|\| __pos < size());
1232	return _M_data()[__pos];
1233	}
1234
1235	/**
1236	* @brief Provides access to the data contained in the %string.
1237	* @param __n The index of the character to access.
1238	* @return Read-only (const) reference to the character.
1239	* @throw std::out_of_range If @a n is an invalid index.
1240	*
1241	* This function provides for safer data access. The parameter is
1242	* first checked that it is in the range of the string. The function
1243	* throws out_of_range if the check fails.
1244	*/
1245	_GLIBCXX20_CONSTEXPR
1246	const_reference
1247	at(size_type __n) const
1248	{
1249	if (__n >= this->size())
1250	__throw_out_of_range_fmt(__N("basic_string::at: __n "
1251	"(which is %zu) >= this->size() "
1252	"(which is %zu)"),
1253	__n, this->size());
1254	return _M_data()[__n];
1255	}
1256
1257	/**
1258	* @brief Provides access to the data contained in the %string.
1259	* @param __n The index of the character to access.
1260	* @return Read/write reference to the character.
1261	* @throw std::out_of_range If @a n is an invalid index.
1262	*
1263	* This function provides for safer data access. The parameter is
1264	* first checked that it is in the range of the string. The function
1265	* throws out_of_range if the check fails.
1266	*/
1267	_GLIBCXX20_CONSTEXPR
1268	reference
1269	at(size_type __n)
1270	{
1271	if (__n >= size())
1272	__throw_out_of_range_fmt(__N("basic_string::at: __n "
1273	"(which is %zu) >= this->size() "
1274	"(which is %zu)"),
1275	__n, this->size());
1276	return _M_data()[__n];
1277	}
1278
1279	#if __cplusplus >= 201103L
1280	/**
1281	* Returns a read/write reference to the data at the first
1282	* element of the %string.
1283	*/
1284	_GLIBCXX20_CONSTEXPR
1285	reference
1286	front() noexcept
1287	{
1288	__glibcxx_assert(!empty());
1289	return operator[](`0`);
1290	}
1291
1292	/**
1293	* Returns a read-only (constant) reference to the data at the first
1294	* element of the %string.
1295	*/
1296	_GLIBCXX20_CONSTEXPR
1297	const_reference
1298	front() const noexcept
1299	{
1300	__glibcxx_assert(!empty());
1301	return operator[](`0`);
1302	}
1303
1304	/**
1305	* Returns a read/write reference to the data at the last
1306	* element of the %string.
1307	*/
1308	_GLIBCXX20_CONSTEXPR
1309	reference
1310	back() noexcept
1311	{
1312	__glibcxx_assert(!empty());
1313	return operator[](this->size() - `1`);
1314	}
1315
1316	/**
1317	* Returns a read-only (constant) reference to the data at the
1318	* last element of the %string.
1319	*/
1320	_GLIBCXX20_CONSTEXPR
1321	const_reference
1322	back() const noexcept
1323	{
1324	__glibcxx_assert(!empty());
1325	return operator[](this->size() - `1`);
1326	}
1327	#endif
1328
1329	// Modifiers:
1330	/**
1331	* @brief Append a string to this string.
1332	* @param __str The string to append.
1333	* @return Reference to this string.
1334	*/
1335	_GLIBCXX20_CONSTEXPR
1336	basic_string&
1337	operator+=(const basic_string& __str)
1338	{ return this->append(__str); }
1339
1340	/**
1341	* @brief Append a C string.
1342	* @param __s The C string to append.
1343	* @return Reference to this string.
1344	*/
1345	_GLIBCXX20_CONSTEXPR
1346	basic_string&
1347	operator+=(const _CharT* __s)
1348	{ return this->append(__s); }
1349
1350	/**
1351	* @brief Append a character.
1352	* @param __c The character to append.
1353	* @return Reference to this string.
1354	*/
1355	_GLIBCXX20_CONSTEXPR
1356	basic_string&
1357	operator+=(_CharT __c)
1358	{
1359	this->push_back(__c);
1360	return *this;
1361	}
1362
1363	#if __cplusplus >= 201103L
1364	/**
1365	* @brief Append an initializer_list of characters.
1366	* @param __l The initializer_list of characters to be appended.
1367	* @return Reference to this string.
1368	*/
1369	_GLIBCXX20_CONSTEXPR
1370	basic_string&
1371	operator+=(initializer_list<_CharT> __l)
1372	{ return this->append(__l.begin(), __l.size()); }
1373	#endif // C++11
1374
1375	#if __cplusplus >= 201703L
1376	/**
1377	* @brief Append a string_view.
1378	* @param __svt An object convertible to string_view to be appended.
1379	* @return Reference to this string.
1380	*/
1381	template<typename _Tp>
1382	_GLIBCXX20_CONSTEXPR
1383	_If_sv<_Tp, basic_string&>
1384	operator+=(const _Tp& __svt)
1385	{ return this->append(__svt); }
1386	#endif // C++17
1387
1388	/**
1389	* @brief Append a string to this string.
1390	* @param __str The string to append.
1391	* @return Reference to this string.
1392	*/
1393	_GLIBCXX20_CONSTEXPR
1394	basic_string&
1395	append(const basic_string& __str)
1396	{ return this->append(__str._M_data(), __str.size()); }
1397
1398	/**
1399	* @brief Append a substring.
1400	* @param __str The string to append.
1401	* @param __pos Index of the first character of str to append.
1402	* @param __n The number of characters to append.
1403	* @return Reference to this string.
1404	* @throw std::out_of_range if @a __pos is not a valid index.
1405	*
1406	* This function appends @a __n characters from @a __str
1407	* starting at @a __pos to this string. If @a __n is is larger
1408	* than the number of available characters in @a __str, the
1409	* remainder of @a __str is appended.
1410	*/
1411	_GLIBCXX20_CONSTEXPR
1412	basic_string&
1413	append(const basic_string& __str, size_type __pos, size_type __n = npos)
1414	{ return this->append(__str._M_data()
1415	+ __str._M_check(__pos, "basic_string::append"),
1416	__str._M_limit(__pos, __n)); }
1417
1418	/**
1419	* @brief Append a C substring.
1420	* @param __s The C string to append.
1421	* @param __n The number of characters to append.
1422	* @return Reference to this string.
1423	*/
1424	_GLIBCXX20_CONSTEXPR
1425	basic_string&
1426	append(const _CharT* __s, size_type __n)
1427	{
1428	__glibcxx_requires_string_len(__s, __n);
1429	_M_check_length(size_type(`0`), __n, "basic_string::append");
1430	return _M_append(__s, __n);
1431	}
1432
1433	/**
1434	* @brief Append a C string.
1435	* @param __s The C string to append.
1436	* @return Reference to this string.
1437	*/
1438	_GLIBCXX20_CONSTEXPR
1439	basic_string&
1440	append(const _CharT* __s)
1441	{
1442	__glibcxx_requires_string(__s);
1443	const size_type __n = traits_type::length(__s);
1444	_M_check_length(size_type(`0`), __n, "basic_string::append");
1445	return _M_append(__s, __n);
1446	}
1447
1448	/**
1449	* @brief Append multiple characters.
1450	* @param __n The number of characters to append.
1451	* @param __c The character to use.
1452	* @return Reference to this string.
1453	*
1454	* Appends __n copies of __c to this string.
1455	*/
1456	_GLIBCXX20_CONSTEXPR
1457	basic_string&
1458	append(size_type __n, _CharT __c)
1459	{ return _M_replace_aux(this->size(), size_type(`0`), __n, __c); }
1460
1461	#if __cplusplus >= 201103L
1462	/**
1463	* @brief Append an initializer_list of characters.
1464	* @param __l The initializer_list of characters to append.
1465	* @return Reference to this string.
1466	*/
1467	_GLIBCXX20_CONSTEXPR
1468	basic_string&
1469	append(initializer_list<_CharT> __l)
1470	{ return this->append(__l.begin(), __l.size()); }
1471	#endif // C++11
1472
1473	/**
1474	* @brief Append a range of characters.
1475	* @param __first Iterator referencing the first character to append.
1476	* @param __last Iterator marking the end of the range.
1477	* @return Reference to this string.
1478	*
1479	* Appends characters in the range [__first,__last) to this string.
1480	*/
1481	#if __cplusplus >= 201103L
1482	template<class _InputIterator,
1483	typename = std::_RequireInputIter<_InputIterator>>
1484	_GLIBCXX20_CONSTEXPR
1485	#else
1486	template<class _InputIterator>
1487	#endif
1488	basic_string&
1489	append(_InputIterator __first, _InputIterator __last)
1490	{ return this->replace(end(), end(), __first, __last); }
1491
1492	#if __cplusplus >= 201703L
1493	/**
1494	* @brief Append a string_view.
1495	* @param __svt An object convertible to string_view to be appended.
1496	* @return Reference to this string.
1497	*/
1498	template<typename _Tp>
1499	_GLIBCXX20_CONSTEXPR
1500	_If_sv<_Tp, basic_string&>
1501	append(const _Tp& __svt)
1502	{
1503	__sv_type __sv = __svt;
1504	return this->append(__sv.data(), __sv.size());
1505	}
1506
1507	/**
1508	* @brief Append a range of characters from a string_view.
1509	* @param __svt An object convertible to string_view to be appended from.
1510	* @param __pos The position in the string_view to append from.
1511	* @param __n The number of characters to append from the string_view.
1512	* @return Reference to this string.
1513	*/
1514	template<typename _Tp>
1515	_GLIBCXX20_CONSTEXPR
1516	_If_sv<_Tp, basic_string&>
1517	append(const _Tp& __svt, size_type __pos, size_type __n = npos)
1518	{
1519	__sv_type __sv = __svt;
1520	return _M_append(__sv.data()
1521	+ std::__sv_check(__sv.size(), __pos, "basic_string::append"),
1522	std::__sv_limit(__sv.size(), __pos, __n));
1523	}
1524	#endif // C++17
1525
1526	/**
1527	* @brief Append a single character.
1528	* @param __c Character to append.
1529	*/
1530	_GLIBCXX20_CONSTEXPR
1531	void
1532	push_back(_CharT __c)
1533	{
1534	const size_type __size = this->size();
1535	if (__size + `1` > this->capacity())
1536	this->_M_mutate(__size, size_type(`0`), `0`, size_type(`1`));
1537	traits_type::assign(this->_M_data()[__size], __c);
1538	this->_M_set_length(__size + `1`);
1539	}
1540
1541	/**
1542	* @brief Set value to contents of another string.
1543	* @param __str Source string to use.
1544	* @return Reference to this string.
1545	*/
1546	_GLIBCXX20_CONSTEXPR
1547	basic_string&
1548	assign(const basic_string& __str)
1549	{
1550	#if __cplusplus >= 201103L
1551	if (_Alloc_traits::_S_propagate_on_copy_assign())
1552	{
1553	if (!_Alloc_traits::_S_always_equal() && !_M_is_local()
1554	&& _M_get_allocator() != __str._M_get_allocator())
1555	{
1556	// Propagating allocator cannot free existing storage so must
1557	// deallocate it before replacing current allocator.
1558	if (__str.size() <= _S_local_capacity)
1559	{
1560	_M_destroy(_M_allocated_capacity);
1561	_M_data(_M_use_local_data());
1562	_M_set_length(`0`);
1563	}
1564	else
1565	{
1566	const auto __len = __str.size();
1567	auto __alloc = __str._M_get_allocator();
1568	// If this allocation throws there are no effects:
1569	auto __ptr = _Alloc_traits::allocate(__alloc, __len + `1`);
1570	_M_destroy(_M_allocated_capacity);
1571	_M_data(__ptr);
1572	_M_capacity(__len);
1573	_M_set_length(__len);
1574	}
1575	}
1576	std::__alloc_on_copy(_M_get_allocator(), __str._M_get_allocator());
1577	}
1578	#endif
1579	this->_M_assign(__str);
1580	return *this;
1581	}
1582
1583	#if __cplusplus >= 201103L
1584	/**
1585	* @brief Set value to contents of another string.
1586	* @param __str Source string to use.
1587	* @return Reference to this string.
1588	*
1589	* This function sets this string to the exact contents of @a __str.
1590	* @a __str is a valid, but unspecified string.
1591	*/
1592	_GLIBCXX20_CONSTEXPR
1593	basic_string&
1594	assign(basic_string&& __str)
1595	noexcept(_Alloc_traits::_S_nothrow_move())
1596	{
1597	// _GLIBCXX_RESOLVE_LIB_DEFECTS
1598	// 2063. Contradictory requirements for string move assignment
1599	return *this = std::move(__str);
1600	}
1601	#endif // C++11
1602
1603	/**
1604	* @brief Set value to a substring of a string.
1605	* @param __str The string to use.
1606	* @param __pos Index of the first character of str.
1607	* @param __n Number of characters to use.
1608	* @return Reference to this string.
1609	* @throw std::out_of_range if @a pos is not a valid index.
1610	*
1611	* This function sets this string to the substring of @a __str
1612	* consisting of @a __n characters at @a __pos. If @a __n is
1613	* is larger than the number of available characters in @a
1614	* __str, the remainder of @a __str is used.
1615	*/
1616	_GLIBCXX20_CONSTEXPR
1617	basic_string&
1618	assign(const basic_string& __str, size_type __pos, size_type __n = npos)
1619	{ return _M_replace(size_type(`0`), this->size(), __str._M_data()
1620	+ __str._M_check(__pos, "basic_string::assign"),
1621	__str._M_limit(__pos, __n)); }
1622
1623	/**
1624	* @brief Set value to a C substring.
1625	* @param __s The C string to use.
1626	* @param __n Number of characters to use.
1627	* @return Reference to this string.
1628	*
1629	* This function sets the value of this string to the first @a __n
1630	* characters of @a __s. If @a __n is is larger than the number of
1631	* available characters in @a __s, the remainder of @a __s is used.
1632	*/
1633	_GLIBCXX20_CONSTEXPR
1634	basic_string&
1635	assign(const _CharT* __s, size_type __n)
1636	{
1637	__glibcxx_requires_string_len(__s, __n);
1638	return _M_replace(size_type(`0`), this->size(), __s, __n);
1639	}
1640
1641	/**
1642	* @brief Set value to contents of a C string.
1643	* @param __s The C string to use.
1644	* @return Reference to this string.
1645	*
1646	* This function sets the value of this string to the value of @a __s.
1647	* The data is copied, so there is no dependence on @a __s once the
1648	* function returns.
1649	*/
1650	_GLIBCXX20_CONSTEXPR
1651	basic_string&
1652	assign(const _CharT* __s)
1653	{
1654	__glibcxx_requires_string(__s);
1655	return _M_replace(size_type(`0`), this->size(), __s,
1656	traits_type::length(__s));
1657	}
1658
1659	/**
1660	* @brief Set value to multiple characters.
1661	* @param __n Length of the resulting string.
1662	* @param __c The character to use.
1663	* @return Reference to this string.
1664	*
1665	* This function sets the value of this string to @a __n copies of
1666	* character @a __c.
1667	*/
1668	_GLIBCXX20_CONSTEXPR
1669	basic_string&
1670	assign(size_type __n, _CharT __c)
1671	{ return _M_replace_aux(size_type(`0`), this->size(), __n, __c); }
1672
1673	/**
1674	* @brief Set value to a range of characters.
1675	* @param __first Iterator referencing the first character to append.
1676	* @param __last Iterator marking the end of the range.
1677	* @return Reference to this string.
1678	*
1679	* Sets value of string to characters in the range [__first,__last).
1680	*/
1681	#if __cplusplus >= 201103L
1682	template<class _InputIterator,
1683	typename = std::_RequireInputIter<_InputIterator>>
1684	_GLIBCXX20_CONSTEXPR
1685	#else
1686	template<class _InputIterator>
1687	#endif
1688	basic_string&
1689	assign(_InputIterator __first, _InputIterator __last)
1690	{ return this->replace(begin(), end(), __first, __last); }
1691
1692	#if __cplusplus >= 201103L
1693	/**
1694	* @brief Set value to an initializer_list of characters.
1695	* @param __l The initializer_list of characters to assign.
1696	* @return Reference to this string.
1697	*/
1698	_GLIBCXX20_CONSTEXPR
1699	basic_string&
1700	assign(initializer_list<_CharT> __l)
1701	{ return this->assign(__l.begin(), __l.size()); }
1702	#endif // C++11
1703
1704	#if __cplusplus >= 201703L
1705	/**
1706	* @brief Set value from a string_view.
1707	* @param __svt The source object convertible to string_view.
1708	* @return Reference to this string.
1709	*/
1710	template<typename _Tp>
1711	_GLIBCXX20_CONSTEXPR
1712	_If_sv<_Tp, basic_string&>
1713	assign(const _Tp& __svt)
1714	{
1715	__sv_type __sv = __svt;
1716	return this->assign(__sv.data(), __sv.size());
1717	}
1718
1719	/**
1720	* @brief Set value from a range of characters in a string_view.
1721	* @param __svt The source object convertible to string_view.
1722	* @param __pos The position in the string_view to assign from.
1723	* @param __n The number of characters to assign.
1724	* @return Reference to this string.
1725	*/
1726	template<typename _Tp>
1727	_GLIBCXX20_CONSTEXPR
1728	_If_sv<_Tp, basic_string&>
1729	assign(const _Tp& __svt, size_type __pos, size_type __n = npos)
1730	{
1731	__sv_type __sv = __svt;
1732	return _M_replace(size_type(`0`), this->size(),
1733	__sv.data()
1734	+ std::__sv_check(__sv.size(), __pos, "basic_string::assign"),
1735	std::__sv_limit(__sv.size(), __pos, __n));
1736	}
1737	#endif // C++17
1738
1739	#if __cplusplus >= 201103L
1740	/**
1741	* @brief Insert multiple characters.
1742	* @param __p Const_iterator referencing location in string to
1743	* insert at.
1744	* @param __n Number of characters to insert
1745	* @param __c The character to insert.
1746	* @return Iterator referencing the first inserted char.
1747	* @throw std::length_error If new length exceeds @c max_size().
1748	*
1749	* Inserts @a __n copies of character @a __c starting at the
1750	* position referenced by iterator @a __p. If adding
1751	* characters causes the length to exceed max_size(),
1752	* length_error is thrown. The value of the string doesn't
1753	* change if an error is thrown.
1754	*/
1755	_GLIBCXX20_CONSTEXPR
1756	iterator
1757	insert(const_iterator __p, size_type __n, _CharT __c)
1758	{
1759	_GLIBCXX_DEBUG_PEDASSERT(__p >= begin() && __p <= end());
1760	const size_type __pos = __p - begin();
1761	this->replace(__p, __p, __n, __c);
1762	return iterator(this->_M_data() + __pos);
1763	}
1764	#else
1765	/**
1766	* @brief Insert multiple characters.
1767	* @param __p Iterator referencing location in string to insert at.
1768	* @param __n Number of characters to insert
1769	* @param __c The character to insert.
1770	* @throw std::length_error If new length exceeds @c max_size().
1771	*
1772	* Inserts @a __n copies of character @a __c starting at the
1773	* position referenced by iterator @a __p. If adding
1774	* characters causes the length to exceed max_size(),
1775	* length_error is thrown. The value of the string doesn't
1776	* change if an error is thrown.
1777	*/
1778	void
1779	insert(iterator __p, size_type __n, _CharT __c)
1780	{ this->replace(__p, __p, __n, __c); }
1781	#endif
1782
1783	#if __cplusplus >= 201103L
1784	/**
1785	* @brief Insert a range of characters.
1786	* @param __p Const_iterator referencing location in string to
1787	* insert at.
1788	* @param __beg Start of range.
1789	* @param __end End of range.
1790	* @return Iterator referencing the first inserted char.
1791	* @throw std::length_error If new length exceeds @c max_size().
1792	*
1793	* Inserts characters in range [beg,end). If adding characters
1794	* causes the length to exceed max_size(), length_error is
1795	* thrown. The value of the string doesn't change if an error
1796	* is thrown.
1797	*/
1798	template<class _InputIterator,
1799	typename = std::_RequireInputIter<_InputIterator>>
1800	_GLIBCXX20_CONSTEXPR
1801	iterator
1802	insert(const_iterator __p, _InputIterator __beg, _InputIterator __end)
1803	{
1804	_GLIBCXX_DEBUG_PEDASSERT(__p >= begin() && __p <= end());
1805	const size_type __pos = __p - begin();
1806	this->replace(__p, __p, __beg, __end);
1807	return iterator(this->_M_data() + __pos);
1808	}
1809	#else
1810	/**
1811	* @brief Insert a range of characters.
1812	* @param __p Iterator referencing location in string to insert at.
1813	* @param __beg Start of range.
1814	* @param __end End of range.
1815	* @throw std::length_error If new length exceeds @c max_size().
1816	*
1817	* Inserts characters in range [__beg,__end). If adding
1818	* characters causes the length to exceed max_size(),
1819	* length_error is thrown. The value of the string doesn't
1820	* change if an error is thrown.
1821	*/
1822	template<class _InputIterator>
1823	void
1824	insert(iterator __p, _InputIterator __beg, _InputIterator __end)
1825	{ this->replace(__p, __p, __beg, __end); }
1826	#endif
1827
1828	#if __cplusplus >= 201103L
1829	/**
1830	* @brief Insert an initializer_list of characters.
1831	* @param __p Iterator referencing location in string to insert at.
1832	* @param __l The initializer_list of characters to insert.
1833	* @throw std::length_error If new length exceeds @c max_size().
1834	*/
1835	_GLIBCXX20_CONSTEXPR
1836	iterator
1837	insert(const_iterator __p, initializer_list<_CharT> __l)
1838	{ return this->insert(__p, __l.begin(), __l.end()); }
1839
1840	#ifdef _GLIBCXX_DEFINING_STRING_INSTANTIATIONS
1841	// See PR libstdc++/83328
1842	void
1843	insert(iterator __p, initializer_list<_CharT> __l)
1844	{
1845	_GLIBCXX_DEBUG_PEDASSERT(__p >= begin() && __p <= end());
1846	this->insert(__p - begin(), __l.begin(), __l.size());
1847	}
1848	#endif
1849	#endif // C++11
1850
1851	/**
1852	* @brief Insert value of a string.
1853	* @param __pos1 Position in string to insert at.
1854	* @param __str The string to insert.
1855	* @return Reference to this string.
1856	* @throw std::length_error If new length exceeds @c max_size().
1857	*
1858	* Inserts value of @a __str starting at @a __pos1. If adding
1859	* characters causes the length to exceed max_size(),
1860	* length_error is thrown. The value of the string doesn't
1861	* change if an error is thrown.
1862	*/
1863	_GLIBCXX20_CONSTEXPR
1864	basic_string&
1865	insert(size_type __pos1, const basic_string& __str)
1866	{ return this->replace(__pos1, size_type(`0`),
1867	__str._M_data(), __str.size()); }
1868
1869	/**
1870	* @brief Insert a substring.
1871	* @param __pos1 Position in string to insert at.
1872	* @param __str The string to insert.
1873	* @param __pos2 Start of characters in str to insert.
1874	* @param __n Number of characters to insert.
1875	* @return Reference to this string.
1876	* @throw std::length_error If new length exceeds @c max_size().
1877	* @throw std::out_of_range If @a pos1 > size() or
1878	* @a __pos2 > @a str.size().
1879	*
1880	* Starting at @a pos1, insert @a __n character of @a __str
1881	* beginning with @a __pos2. If adding characters causes the
1882	* length to exceed max_size(), length_error is thrown. If @a
1883	* __pos1 is beyond the end of this string or @a __pos2 is
1884	* beyond the end of @a __str, out_of_range is thrown. The
1885	* value of the string doesn't change if an error is thrown.
1886	*/
1887	_GLIBCXX20_CONSTEXPR
1888	basic_string&
1889	insert(size_type __pos1, const basic_string& __str,
1890	size_type __pos2, size_type __n = npos)
1891	{ return this->replace(__pos1, size_type(`0`), __str._M_data()
1892	+ __str._M_check(__pos2, "basic_string::insert"),
1893	__str._M_limit(__pos2, __n)); }
1894
1895	/**
1896	* @brief Insert a C substring.
1897	* @param __pos Position in string to insert at.
1898	* @param __s The C string to insert.
1899	* @param __n The number of characters to insert.
1900	* @return Reference to this string.
1901	* @throw std::length_error If new length exceeds @c max_size().
1902	* @throw std::out_of_range If @a __pos is beyond the end of this
1903	* string.
1904	*
1905	* Inserts the first @a __n characters of @a __s starting at @a
1906	* __pos. If adding characters causes the length to exceed
1907	* max_size(), length_error is thrown. If @a __pos is beyond
1908	* end(), out_of_range is thrown. The value of the string
1909	* doesn't change if an error is thrown.
1910	*/
1911	_GLIBCXX20_CONSTEXPR
1912	basic_string&
1913	insert(size_type __pos, const _CharT* __s, size_type __n)
1914	{ return this->replace(__pos, size_type(`0`), __s, __n); }
1915
1916	/**
1917	* @brief Insert a C string.
1918	* @param __pos Position in string to insert at.
1919	* @param __s The C string to insert.
1920	* @return Reference to this string.
1921	* @throw std::length_error If new length exceeds @c max_size().
1922	* @throw std::out_of_range If @a pos is beyond the end of this
1923	* string.
1924	*
1925	* Inserts the first @a n characters of @a __s starting at @a __pos. If
1926	* adding characters causes the length to exceed max_size(),
1927	* length_error is thrown. If @a __pos is beyond end(), out_of_range is
1928	* thrown. The value of the string doesn't change if an error is
1929	* thrown.
1930	*/
1931	_GLIBCXX20_CONSTEXPR
1932	basic_string&
1933	insert(size_type __pos, const _CharT* __s)
1934	{
1935	__glibcxx_requires_string(__s);
1936	return this->replace(__pos, size_type(`0`), __s,
1937	traits_type::length(__s));
1938	}
1939
1940	/**
1941	* @brief Insert multiple characters.
1942	* @param __pos Index in string to insert at.
1943	* @param __n Number of characters to insert
1944	* @param __c The character to insert.
1945	* @return Reference to this string.
1946	* @throw std::length_error If new length exceeds @c max_size().
1947	* @throw std::out_of_range If @a __pos is beyond the end of this
1948	* string.
1949	*
1950	* Inserts @a __n copies of character @a __c starting at index
1951	* @a __pos. If adding characters causes the length to exceed
1952	* max_size(), length_error is thrown. If @a __pos > length(),
1953	* out_of_range is thrown. The value of the string doesn't
1954	* change if an error is thrown.
1955	*/
1956	_GLIBCXX20_CONSTEXPR
1957	basic_string&
1958	insert(size_type __pos, size_type __n, _CharT __c)
1959	{ return _M_replace_aux(_M_check(__pos, "basic_string::insert"),
1960	size_type(`0`), __n, __c); }
1961
1962	/**
1963	* @brief Insert one character.
1964	* @param __p Iterator referencing position in string to insert at.
1965	* @param __c The character to insert.
1966	* @return Iterator referencing newly inserted char.
1967	* @throw std::length_error If new length exceeds @c max_size().
1968	*
1969	* Inserts character @a __c at position referenced by @a __p.
1970	* If adding character causes the length to exceed max_size(),
1971	* length_error is thrown. If @a __p is beyond end of string,
1972	* out_of_range is thrown. The value of the string doesn't
1973	* change if an error is thrown.
1974	*/
1975	_GLIBCXX20_CONSTEXPR
1976	iterator
1977	insert(__const_iterator __p, _CharT __c)
1978	{
1979	_GLIBCXX_DEBUG_PEDASSERT(__p >= begin() && __p <= end());
1980	const size_type __pos = __p - begin();
1981	_M_replace_aux(__pos, size_type(`0`), size_type(`1`), __c);
1982	return iterator(_M_data() + __pos);
1983	}
1984
1985	#if __cplusplus >= 201703L
1986	/**
1987	* @brief Insert a string_view.
1988	* @param __pos Position in string to insert at.
1989	* @param __svt The object convertible to string_view to insert.
1990	* @return Reference to this string.
1991	*/
1992	template<typename _Tp>
1993	_GLIBCXX20_CONSTEXPR
1994	_If_sv<_Tp, basic_string&>
1995	insert(size_type __pos, const _Tp& __svt)
1996	{
1997	__sv_type __sv = __svt;
1998	return this->insert(__pos, __sv.data(), __sv.size());
1999	}
2000
2001	/**
2002	* @brief Insert a string_view.
2003	* @param __pos1 Position in string to insert at.
2004	* @param __svt The object convertible to string_view to insert from.
2005	* @param __pos2 Start of characters in str to insert.
2006	* @param __n The number of characters to insert.
2007	* @return Reference to this string.
2008	*/
2009	template<typename _Tp>
2010	_GLIBCXX20_CONSTEXPR
2011	_If_sv<_Tp, basic_string&>
2012	insert(size_type __pos1, const _Tp& __svt,
2013	size_type __pos2, size_type __n = npos)
2014	{
2015	__sv_type __sv = __svt;
2016	return this->replace(__pos1, size_type(`0`),
2017	__sv.data()
2018	+ std::__sv_check(__sv.size(), __pos2, "basic_string::insert"),
2019	std::__sv_limit(__sv.size(), __pos2, __n));
2020	}
2021	#endif // C++17
2022
2023	/**
2024	* @brief Remove characters.
2025	* @param __pos Index of first character to remove (default 0).
2026	* @param __n Number of characters to remove (default remainder).
2027	* @return Reference to this string.
2028	* @throw std::out_of_range If @a pos is beyond the end of this
2029	* string.
2030	*
2031	* Removes @a __n characters from this string starting at @a
2032	* __pos. The length of the string is reduced by @a __n. If
2033	* there are < @a __n characters to remove, the remainder of
2034	* the string is truncated. If @a __p is beyond end of string,
2035	* out_of_range is thrown. The value of the string doesn't
2036	* change if an error is thrown.
2037	*/
2038	_GLIBCXX20_CONSTEXPR
2039	basic_string&
2040	erase(size_type __pos = `0`, size_type __n = npos)
2041	{
2042	_M_check(__pos, "basic_string::erase");
2043	if (__n == npos)
2044	this->_M_set_length(__pos);
2045	else if (__n != `0`)
2046	this->_M_erase(__pos, _M_limit(__pos, __n));
2047	return *this;
2048	}
2049
2050	/**
2051	* @brief Remove one character.
2052	* @param __position Iterator referencing the character to remove.
2053	* @return iterator referencing same location after removal.
2054	*
2055	* Removes the character at @a __position from this string. The value
2056	* of the string doesn't change if an error is thrown.
2057	*/
2058	_GLIBCXX20_CONSTEXPR
2059	iterator
2060	erase(__const_iterator __position)
2061	{
2062	_GLIBCXX_DEBUG_PEDASSERT(__position >= begin()
2063	&& __position < end());
2064	const size_type __pos = __position - begin();
2065	this->_M_erase(__pos, size_type(`1`));
2066	return iterator(_M_data() + __pos);
2067	}
2068
2069	/**
2070	* @brief Remove a range of characters.
2071	* @param __first Iterator referencing the first character to remove.
2072	* @param __last Iterator referencing the end of the range.
2073	* @return Iterator referencing location of first after removal.
2074	*
2075	* Removes the characters in the range [first,last) from this string.
2076	* The value of the string doesn't change if an error is thrown.
2077	*/
2078	_GLIBCXX20_CONSTEXPR
2079	iterator
2080	erase(__const_iterator __first, __const_iterator __last)
2081	{
2082	_GLIBCXX_DEBUG_PEDASSERT(__first >= begin() && __first <= __last
2083	&& __last <= end());
2084	const size_type __pos = __first - begin();
2085	if (__last == end())
2086	this->_M_set_length(__pos);
2087	else
2088	this->_M_erase(__pos, __last - __first);
2089	return iterator(this->_M_data() + __pos);
2090	}
2091
2092	#if __cplusplus >= 201103L
2093	/**
2094	* @brief Remove the last character.
2095	*
2096	* The string must be non-empty.
2097	*/
2098	_GLIBCXX20_CONSTEXPR
2099	void
2100	pop_back() noexcept
2101	{
2102	__glibcxx_assert(!empty());
2103	_M_erase(size() - `1`, `1`);
2104	}
2105	#endif // C++11
2106
2107	/**
2108	* @brief Replace characters with value from another string.
2109	* @param __pos Index of first character to replace.
2110	* @param __n Number of characters to be replaced.
2111	* @param __str String to insert.
2112	* @return Reference to this string.
2113	* @throw std::out_of_range If @a pos is beyond the end of this
2114	* string.
2115	* @throw std::length_error If new length exceeds @c max_size().
2116	*
2117	* Removes the characters in the range [__pos,__pos+__n) from
2118	* this string. In place, the value of @a __str is inserted.
2119	* If @a __pos is beyond end of string, out_of_range is thrown.
2120	* If the length of the result exceeds max_size(), length_error
2121	* is thrown. The value of the string doesn't change if an
2122	* error is thrown.
2123	*/
2124	_GLIBCXX20_CONSTEXPR
2125	basic_string&
2126	replace(size_type __pos, size_type __n, const basic_string& __str)
2127	{ return this->replace(__pos, __n, __str._M_data(), __str.size()); }
2128
2129	/**
2130	* @brief Replace characters with value from another string.
2131	* @param __pos1 Index of first character to replace.
2132	* @param __n1 Number of characters to be replaced.
2133	* @param __str String to insert.
2134	* @param __pos2 Index of first character of str to use.
2135	* @param __n2 Number of characters from str to use.
2136	* @return Reference to this string.
2137	* @throw std::out_of_range If @a __pos1 > size() or @a __pos2 >
2138	* __str.size().
2139	* @throw std::length_error If new length exceeds @c max_size().
2140	*
2141	* Removes the characters in the range [__pos1,__pos1 + n) from this
2142	* string. In place, the value of @a __str is inserted. If @a __pos is
2143	* beyond end of string, out_of_range is thrown. If the length of the
2144	* result exceeds max_size(), length_error is thrown. The value of the
2145	* string doesn't change if an error is thrown.
2146	*/
2147	_GLIBCXX20_CONSTEXPR
2148	basic_string&
2149	replace(size_type __pos1, size_type __n1, const basic_string& __str,
2150	size_type __pos2, size_type __n2 = npos)
2151	{ return this->replace(__pos1, __n1, __str._M_data()
2152	+ __str._M_check(__pos2, "basic_string::replace"),
2153	__str._M_limit(__pos2, __n2)); }
2154
2155	/**
2156	* @brief Replace characters with value of a C substring.
2157	* @param __pos Index of first character to replace.
2158	* @param __n1 Number of characters to be replaced.
2159	* @param __s C string to insert.
2160	* @param __n2 Number of characters from @a s to use.
2161	* @return Reference to this string.
2162	* @throw std::out_of_range If @a pos1 > size().
2163	* @throw std::length_error If new length exceeds @c max_size().
2164	*
2165	* Removes the characters in the range [__pos,__pos + __n1)
2166	* from this string. In place, the first @a __n2 characters of
2167	* @a __s are inserted, or all of @a __s if @a __n2 is too large. If
2168	* @a __pos is beyond end of string, out_of_range is thrown. If
2169	* the length of result exceeds max_size(), length_error is
2170	* thrown. The value of the string doesn't change if an error
2171	* is thrown.
2172	*/
2173	_GLIBCXX20_CONSTEXPR
2174	basic_string&
2175	replace(size_type __pos, size_type __n1, const _CharT* __s,
2176	size_type __n2)
2177	{
2178	__glibcxx_requires_string_len(__s, __n2);
2179	return _M_replace(_M_check(__pos, "basic_string::replace"),
2180	_M_limit(__pos, __n1), __s, __n2);
2181	}
2182
2183	/**
2184	* @brief Replace characters with value of a C string.
2185	* @param __pos Index of first character to replace.
2186	* @param __n1 Number of characters to be replaced.
2187	* @param __s C string to insert.
2188	* @return Reference to this string.
2189	* @throw std::out_of_range If @a pos > size().
2190	* @throw std::length_error If new length exceeds @c max_size().
2191	*
2192	* Removes the characters in the range [__pos,__pos + __n1)
2193	* from this string. In place, the characters of @a __s are
2194	* inserted. If @a __pos is beyond end of string, out_of_range
2195	* is thrown. If the length of result exceeds max_size(),
2196	* length_error is thrown. The value of the string doesn't
2197	* change if an error is thrown.
2198	*/
2199	_GLIBCXX20_CONSTEXPR
2200	basic_string&
2201	replace(size_type __pos, size_type __n1, const _CharT* __s)
2202	{
2203	__glibcxx_requires_string(__s);
2204	return this->replace(__pos, __n1, __s, traits_type::length(__s));
2205	}
2206
2207	/**
2208	* @brief Replace characters with multiple characters.
2209	* @param __pos Index of first character to replace.
2210	* @param __n1 Number of characters to be replaced.
2211	* @param __n2 Number of characters to insert.
2212	* @param __c Character to insert.
2213	* @return Reference to this string.
2214	* @throw std::out_of_range If @a __pos > size().
2215	* @throw std::length_error If new length exceeds @c max_size().
2216	*
2217	* Removes the characters in the range [pos,pos + n1) from this
2218	* string. In place, @a __n2 copies of @a __c are inserted.
2219	* If @a __pos is beyond end of string, out_of_range is thrown.
2220	* If the length of result exceeds max_size(), length_error is
2221	* thrown. The value of the string doesn't change if an error
2222	* is thrown.
2223	*/
2224	_GLIBCXX20_CONSTEXPR
2225	basic_string&
2226	replace(size_type __pos, size_type __n1, size_type __n2, _CharT __c)
2227	{ return _M_replace_aux(_M_check(__pos, "basic_string::replace"),
2228	_M_limit(__pos, __n1), __n2, __c); }
2229
2230	/**
2231	* @brief Replace range of characters with string.
2232	* @param __i1 Iterator referencing start of range to replace.
2233	* @param __i2 Iterator referencing end of range to replace.
2234	* @param __str String value to insert.
2235	* @return Reference to this string.
2236	* @throw std::length_error If new length exceeds @c max_size().
2237	*
2238	* Removes the characters in the range [__i1,__i2). In place,
2239	* the value of @a __str is inserted. If the length of result
2240	* exceeds max_size(), length_error is thrown. The value of
2241	* the string doesn't change if an error is thrown.
2242	*/
2243	_GLIBCXX20_CONSTEXPR
2244	basic_string&
2245	replace(__const_iterator __i1, __const_iterator __i2,
2246	const basic_string& __str)
2247	{ return this->replace(__i1, __i2, __str._M_data(), __str.size()); }
2248
2249	/**
2250	* @brief Replace range of characters with C substring.
2251	* @param __i1 Iterator referencing start of range to replace.
2252	* @param __i2 Iterator referencing end of range to replace.
2253	* @param __s C string value to insert.
2254	* @param __n Number of characters from s to insert.
2255	* @return Reference to this string.
2256	* @throw std::length_error If new length exceeds @c max_size().
2257	*
2258	* Removes the characters in the range [__i1,__i2). In place,
2259	* the first @a __n characters of @a __s are inserted. If the
2260	* length of result exceeds max_size(), length_error is thrown.
2261	* The value of the string doesn't change if an error is
2262	* thrown.
2263	*/
2264	_GLIBCXX20_CONSTEXPR
2265	basic_string&
2266	replace(__const_iterator __i1, __const_iterator __i2,
2267	const _CharT* __s, size_type __n)
2268	{
2269	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2270	&& __i2 <= end());
2271	return this->replace(__i1 - begin(), __i2 - __i1, __s, __n);
2272	}
2273
2274	/**
2275	* @brief Replace range of characters with C string.
2276	* @param __i1 Iterator referencing start of range to replace.
2277	* @param __i2 Iterator referencing end of range to replace.
2278	* @param __s C string value to insert.
2279	* @return Reference to this string.
2280	* @throw std::length_error If new length exceeds @c max_size().
2281	*
2282	* Removes the characters in the range [__i1,__i2). In place,
2283	* the characters of @a __s are inserted. If the length of
2284	* result exceeds max_size(), length_error is thrown. The
2285	* value of the string doesn't change if an error is thrown.
2286	*/
2287	_GLIBCXX20_CONSTEXPR
2288	basic_string&
2289	replace(__const_iterator __i1, __const_iterator __i2, const _CharT* __s)
2290	{
2291	__glibcxx_requires_string(__s);
2292	return this->replace(__i1, __i2, __s, traits_type::length(__s));
2293	}
2294
2295	/**
2296	* @brief Replace range of characters with multiple characters
2297	* @param __i1 Iterator referencing start of range to replace.
2298	* @param __i2 Iterator referencing end of range to replace.
2299	* @param __n Number of characters to insert.
2300	* @param __c Character to insert.
2301	* @return Reference to this string.
2302	* @throw std::length_error If new length exceeds @c max_size().
2303	*
2304	* Removes the characters in the range [__i1,__i2). In place,
2305	* @a __n copies of @a __c are inserted. If the length of
2306	* result exceeds max_size(), length_error is thrown. The
2307	* value of the string doesn't change if an error is thrown.
2308	*/
2309	_GLIBCXX20_CONSTEXPR
2310	basic_string&
2311	replace(__const_iterator __i1, __const_iterator __i2, size_type __n,
2312	_CharT __c)
2313	{
2314	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2315	&& __i2 <= end());
2316	return _M_replace_aux(__i1 - begin(), __i2 - __i1, __n, __c);
2317	}
2318
2319	/**
2320	* @brief Replace range of characters with range.
2321	* @param __i1 Iterator referencing start of range to replace.
2322	* @param __i2 Iterator referencing end of range to replace.
2323	* @param __k1 Iterator referencing start of range to insert.
2324	* @param __k2 Iterator referencing end of range to insert.
2325	* @return Reference to this string.
2326	* @throw std::length_error If new length exceeds @c max_size().
2327	*
2328	* Removes the characters in the range [__i1,__i2). In place,
2329	* characters in the range [__k1,__k2) are inserted. If the
2330	* length of result exceeds max_size(), length_error is thrown.
2331	* The value of the string doesn't change if an error is
2332	* thrown.
2333	*/
2334	#if __cplusplus >= 201103L
2335	template<class _InputIterator,
2336	typename = std::_RequireInputIter<_InputIterator>>
2337	_GLIBCXX20_CONSTEXPR
2338	basic_string&
2339	replace(const_iterator __i1, const_iterator __i2,
2340	_InputIterator __k1, _InputIterator __k2)
2341	{
2342	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2343	&& __i2 <= end());
2344	__glibcxx_requires_valid_range(__k1, __k2);
2345	return this->_M_replace_dispatch(__i1, __i2, __k1, __k2,
2346	std::__false_type ());
2347	}
2348	#else
2349	template<class _InputIterator>
2350	#ifdef _GLIBCXX_DISAMBIGUATE_REPLACE_INST
2351	typename __enable_if_not_native_iterator<_InputIterator>::__type
2352	#else
2353	basic_string&
2354	#endif
2355	replace(iterator __i1, iterator __i2,
2356	_InputIterator __k1, _InputIterator __k2)
2357	{
2358	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2359	&& __i2 <= end());
2360	__glibcxx_requires_valid_range(__k1, __k2);
2361	typedef typename std::__is_integer<_InputIterator>::__type _Integral;
2362	return _M_replace_dispatch(__i1, __i2, __k1, __k2, _Integral());
2363	}
2364	#endif
2365
2366	// Specializations for the common case of pointer and iterator:
2367	// useful to avoid the overhead of temporary buffering in _M_replace.
2368	_GLIBCXX20_CONSTEXPR
2369	basic_string&
2370	replace(__const_iterator __i1, __const_iterator __i2,
2371	_CharT* __k1, _CharT* __k2)
2372	{
2373	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2374	&& __i2 <= end());
2375	__glibcxx_requires_valid_range(__k1, __k2);
2376	return this->replace(__i1 - begin(), __i2 - __i1,
2377	__k1, __k2 - __k1);
2378	}
2379
2380	_GLIBCXX20_CONSTEXPR
2381	basic_string&
2382	replace(__const_iterator __i1, __const_iterator __i2,
2383	const _CharT* __k1, const _CharT* __k2)
2384	{
2385	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2386	&& __i2 <= end());
2387	__glibcxx_requires_valid_range(__k1, __k2);
2388	return this->replace(__i1 - begin(), __i2 - __i1,
2389	__k1, __k2 - __k1);
2390	}
2391
2392	_GLIBCXX20_CONSTEXPR
2393	basic_string&
2394	replace(__const_iterator __i1, __const_iterator __i2,
2395	iterator __k1, iterator __k2)
2396	{
2397	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2398	&& __i2 <= end());
2399	__glibcxx_requires_valid_range(__k1, __k2);
2400	return this->replace(__i1 - begin(), __i2 - __i1,
2401	__k1.base(), __k2 - __k1);
2402	}
2403
2404	_GLIBCXX20_CONSTEXPR
2405	basic_string&
2406	replace(__const_iterator __i1, __const_iterator __i2,
2407	const_iterator __k1, const_iterator __k2)
2408	{
2409	_GLIBCXX_DEBUG_PEDASSERT(begin() <= __i1 && __i1 <= __i2
2410	&& __i2 <= end());
2411	__glibcxx_requires_valid_range(__k1, __k2);
2412	return this->replace(__i1 - begin(), __i2 - __i1,
2413	__k1.base(), __k2 - __k1);
2414	}
2415
2416	#if __cplusplus >= 201103L
2417	/**
2418	* @brief Replace range of characters with initializer_list.
2419	* @param __i1 Iterator referencing start of range to replace.
2420	* @param __i2 Iterator referencing end of range to replace.
2421	* @param __l The initializer_list of characters to insert.
2422	* @return Reference to this string.
2423	* @throw std::length_error If new length exceeds @c max_size().
2424	*
2425	* Removes the characters in the range [__i1,__i2). In place,
2426	* characters in the range [__k1,__k2) are inserted. If the
2427	* length of result exceeds max_size(), length_error is thrown.
2428	* The value of the string doesn't change if an error is
2429	* thrown.
2430	*/
2431	_GLIBCXX20_CONSTEXPR
2432	basic_string& replace(const_iterator __i1, const_iterator __i2,
2433	initializer_list<_CharT> __l)
2434	{ return this->replace(__i1, __i2, __l.begin(), __l.size()); }
2435	#endif // C++11
2436
2437	#if __cplusplus >= 201703L
2438	/**
2439	* @brief Replace range of characters with string_view.
2440	* @param __pos The position to replace at.
2441	* @param __n The number of characters to replace.
2442	* @param __svt The object convertible to string_view to insert.
2443	* @return Reference to this string.
2444	*/
2445	template<typename _Tp>
2446	_GLIBCXX20_CONSTEXPR
2447	_If_sv<_Tp, basic_string&>
2448	replace(size_type __pos, size_type __n, const _Tp& __svt)
2449	{
2450	__sv_type __sv = __svt;
2451	return this->replace(__pos, __n, __sv.data(), __sv.size());
2452	}
2453
2454	/**
2455	* @brief Replace range of characters with string_view.
2456	* @param __pos1 The position to replace at.
2457	* @param __n1 The number of characters to replace.
2458	* @param __svt The object convertible to string_view to insert from.
2459	* @param __pos2 The position in the string_view to insert from.
2460	* @param __n2 The number of characters to insert.
2461	* @return Reference to this string.
2462	*/
2463	template<typename _Tp>
2464	_GLIBCXX20_CONSTEXPR
2465	_If_sv<_Tp, basic_string&>
2466	replace(size_type __pos1, size_type __n1, const _Tp& __svt,
2467	size_type __pos2, size_type __n2 = npos)
2468	{
2469	__sv_type __sv = __svt;
2470	return this->replace(__pos1, __n1,
2471	__sv.data()
2472	+ std::__sv_check(__sv.size(), __pos2, "basic_string::replace"),
2473	std::__sv_limit(__sv.size(), __pos2, __n2));
2474	}
2475
2476	/**
2477	* @brief Replace range of characters with string_view.
2478	* @param __i1 An iterator referencing the start position
2479	to replace at.
2480	* @param __i2 An iterator referencing the end position
2481	for the replace.
2482	* @param __svt The object convertible to string_view to insert from.
2483	* @return Reference to this string.
2484	*/
2485	template<typename _Tp>
2486	_GLIBCXX20_CONSTEXPR
2487	_If_sv<_Tp, basic_string&>
2488	replace(const_iterator __i1, const_iterator __i2, const _Tp& __svt)
2489	{
2490	__sv_type __sv = __svt;
2491	return this->replace(__i1 - begin(), __i2 - __i1, __sv);
2492	}
2493	#endif // C++17
2494
2495	private:
2496	template<class _Integer>
2497	_GLIBCXX20_CONSTEXPR
2498	basic_string&
2499	_M_replace_dispatch(const_iterator __i1, const_iterator __i2,
2500	_Integer __n, _Integer __val, __true_type)
2501	{ return _M_replace_aux(__i1 - begin(), __i2 - __i1, __n, __val); }
2502
2503	template<class _InputIterator>
2504	_GLIBCXX20_CONSTEXPR
2505	basic_string&
2506	_M_replace_dispatch(const_iterator __i1, const_iterator __i2,
2507	_InputIterator __k1, _InputIterator __k2,
2508	__false_type);
2509
2510	_GLIBCXX20_CONSTEXPR
2511	basic_string&
2512	_M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
2513	_CharT __c);
2514
2515	_GLIBCXX20_CONSTEXPR
2516	basic_string&
2517	_M_replace(size_type __pos, size_type __len1, const _CharT* __s,
2518	const size_type __len2);
2519
2520	_GLIBCXX20_CONSTEXPR
2521	basic_string&
2522	_M_append(const _CharT* __s, size_type __n);
2523
2524	public:
2525
2526	/**
2527	* @brief Copy substring into C string.
2528	* @param __s C string to copy value into.
2529	* @param __n Number of characters to copy.
2530	* @param __pos Index of first character to copy.
2531	* @return Number of characters actually copied
2532	* @throw std::out_of_range If __pos > size().
2533	*
2534	* Copies up to @a __n characters starting at @a __pos into the
2535	* C string @a __s. If @a __pos is %greater than size(),
2536	* out_of_range is thrown.
2537	*/
2538	_GLIBCXX20_CONSTEXPR
2539	size_type
2540	copy(_CharT* __s, size_type __n, size_type __pos = `0`) const;
2541
2542	/**
2543	* @brief Swap contents with another string.
2544	* @param __s String to swap with.
2545	*
2546	* Exchanges the contents of this string with that of @a __s in constant
2547	* time.
2548	*/
2549	_GLIBCXX20_CONSTEXPR
2550	void
2551	swap(basic_string& __s) _GLIBCXX_NOEXCEPT;
2552
2553	// String operations:
2554	/**
2555	* @brief Return const pointer to null-terminated contents.
2556	*
2557	* This is a handle to internal data. Do not modify or dire things may
2558	* happen.
2559	*/
2560	_GLIBCXX20_CONSTEXPR
2561	const _CharT*
2562	c_str() const _GLIBCXX_NOEXCEPT
2563	{ return _M_data(); }
2564
2565	/**
2566	* @brief Return const pointer to contents.
2567	*
2568	* This is a pointer to internal data. It is undefined to modify
2569	* the contents through the returned pointer. To get a pointer that
2570	* allows modifying the contents use @c &str[0] instead,
2571	* (or in C++17 the non-const @c str.data() overload).
2572	*/
2573	_GLIBCXX20_CONSTEXPR
2574	const _CharT*
2575	data() const _GLIBCXX_NOEXCEPT
2576	{ return _M_data(); }
2577
2578	#if __cplusplus >= 201703L
2579	/**
2580	* @brief Return non-const pointer to contents.
2581	*
2582	* This is a pointer to the character sequence held by the string.
2583	* Modifying the characters in the sequence is allowed.
2584	*/
2585	_GLIBCXX20_CONSTEXPR
2586	_CharT*
2587	data() noexcept
2588	{ return _M_data(); }
2589	#endif
2590
2591	/**
2592	* @brief Return copy of allocator used to construct this string.
2593	*/
2594	_GLIBCXX20_CONSTEXPR
2595	allocator_type
2596	get_allocator() const _GLIBCXX_NOEXCEPT
2597	{ return _M_get_allocator(); }
2598
2599	/**
2600	* @brief Find position of a C substring.
2601	* @param __s C string to locate.
2602	* @param __pos Index of character to search from.
2603	* @param __n Number of characters from @a s to search for.
2604	* @return Index of start of first occurrence.
2605	*
2606	* Starting from @a __pos, searches forward for the first @a
2607	* __n characters in @a __s within this string. If found,
2608	* returns the index where it begins. If not found, returns
2609	* npos.
2610	*/
2611	_GLIBCXX20_CONSTEXPR
2612	size_type
2613	find(const _CharT* __s, size_type __pos, size_type __n) const
2614	_GLIBCXX_NOEXCEPT;
2615
2616	/**
2617	* @brief Find position of a string.
2618	* @param __str String to locate.
2619	* @param __pos Index of character to search from (default 0).
2620	* @return Index of start of first occurrence.
2621	*
2622	* Starting from @a __pos, searches forward for value of @a __str within
2623	* this string. If found, returns the index where it begins. If not
2624	* found, returns npos.
2625	*/
2626	_GLIBCXX20_CONSTEXPR
2627	size_type
2628	find(const basic_string& __str, size_type __pos = `0`) const
2629	_GLIBCXX_NOEXCEPT
2630	{ return this->find(__str.data(), __pos, __str.size()); }
2631
2632	#if __cplusplus >= 201703L
2633	/**
2634	* @brief Find position of a string_view.
2635	* @param __svt The object convertible to string_view to locate.
2636	* @param __pos Index of character to search from (default 0).
2637	* @return Index of start of first occurrence.
2638	*/
2639	template<typename _Tp>
2640	_GLIBCXX20_CONSTEXPR
2641	_If_sv<_Tp, size_type>
2642	find(const _Tp& __svt, size_type __pos = `0`) const
2643	noexcept(is_same<_Tp, __sv_type>::value)
2644	{
2645	__sv_type __sv = __svt;
2646	return this->find(__sv.data(), __pos, __sv.size());
2647	}
2648	#endif // C++17
2649
2650	/**
2651	* @brief Find position of a C string.
2652	* @param __s C string to locate.
2653	* @param __pos Index of character to search from (default 0).
2654	* @return Index of start of first occurrence.
2655	*
2656	* Starting from @a __pos, searches forward for the value of @a
2657	* __s within this string. If found, returns the index where
2658	* it begins. If not found, returns npos.
2659	*/
2660	_GLIBCXX20_CONSTEXPR
2661	size_type
2662	find(const _CharT* __s, size_type __pos = `0`) const _GLIBCXX_NOEXCEPT
2663	{
2664	__glibcxx_requires_string(__s);
2665	return this->find(__s, __pos, traits_type::length(__s));
2666	}
2667
2668	/**
2669	* @brief Find position of a character.
2670	* @param __c Character to locate.
2671	* @param __pos Index of character to search from (default 0).
2672	* @return Index of first occurrence.
2673	*
2674	* Starting from @a __pos, searches forward for @a __c within
2675	* this string. If found, returns the index where it was
2676	* found. If not found, returns npos.
2677	*/
2678	_GLIBCXX20_CONSTEXPR
2679	size_type
2680	find(_CharT __c, size_type __pos = `0`) const _GLIBCXX_NOEXCEPT;
2681
2682	/**
2683	* @brief Find last position of a string.
2684	* @param __str String to locate.
2685	* @param __pos Index of character to search back from (default end).
2686	* @return Index of start of last occurrence.
2687	*
2688	* Starting from @a __pos, searches backward for value of @a
2689	* __str within this string. If found, returns the index where
2690	* it begins. If not found, returns npos.
2691	*/
2692	_GLIBCXX20_CONSTEXPR
2693	size_type
2694	rfind(const basic_string& __str, size_type __pos = npos) const
2695	_GLIBCXX_NOEXCEPT
2696	{ return this->rfind(__str.data(), __pos, __str.size()); }
2697
2698	#if __cplusplus >= 201703L
2699	/**
2700	* @brief Find last position of a string_view.
2701	* @param __svt The object convertible to string_view to locate.
2702	* @param __pos Index of character to search back from (default end).
2703	* @return Index of start of last occurrence.
2704	*/
2705	template<typename _Tp>
2706	_GLIBCXX20_CONSTEXPR
2707	_If_sv<_Tp, size_type>
2708	rfind(const _Tp& __svt, size_type __pos = npos) const
2709	noexcept(is_same<_Tp, __sv_type>::value)
2710	{
2711	__sv_type __sv = __svt;
2712	return this->rfind(__sv.data(), __pos, __sv.size());
2713	}
2714	#endif // C++17
2715
2716	/**
2717	* @brief Find last position of a C substring.
2718	* @param __s C string to locate.
2719	* @param __pos Index of character to search back from.
2720	* @param __n Number of characters from s to search for.
2721	* @return Index of start of last occurrence.
2722	*
2723	* Starting from @a __pos, searches backward for the first @a
2724	* __n characters in @a __s within this string. If found,
2725	* returns the index where it begins. If not found, returns
2726	* npos.
2727	*/
2728	_GLIBCXX20_CONSTEXPR
2729	size_type
2730	rfind(const _CharT* __s, size_type __pos, size_type __n) const
2731	_GLIBCXX_NOEXCEPT;
2732
2733	/**
2734	* @brief Find last position of a C string.
2735	* @param __s C string to locate.
2736	* @param __pos Index of character to start search at (default end).
2737	* @return Index of start of last occurrence.
2738	*
2739	* Starting from @a __pos, searches backward for the value of
2740	* @a __s within this string. If found, returns the index
2741	* where it begins. If not found, returns npos.
2742	*/
2743	_GLIBCXX20_CONSTEXPR
2744	size_type
2745	rfind(const _CharT* __s, size_type __pos = npos) const
2746	{
2747	__glibcxx_requires_string(__s);
2748	return this->rfind(__s, __pos, traits_type::length(__s));
2749	}
2750
2751	/**
2752	* @brief Find last position of a character.
2753	* @param __c Character to locate.
2754	* @param __pos Index of character to search back from (default end).
2755	* @return Index of last occurrence.
2756	*
2757	* Starting from @a __pos, searches backward for @a __c within
2758	* this string. If found, returns the index where it was
2759	* found. If not found, returns npos.
2760	*/
2761	_GLIBCXX20_CONSTEXPR
2762	size_type
2763	rfind(_CharT __c, size_type __pos = npos) const _GLIBCXX_NOEXCEPT;
2764
2765	/**
2766	* @brief Find position of a character of string.
2767	* @param __str String containing characters to locate.
2768	* @param __pos Index of character to search from (default 0).
2769	* @return Index of first occurrence.
2770	*
2771	* Starting from @a __pos, searches forward for one of the
2772	* characters of @a __str within this string. If found,
2773	* returns the index where it was found. If not found, returns
2774	* npos.
2775	*/
2776	_GLIBCXX20_CONSTEXPR
2777	size_type
2778	find_first_of(const basic_string& __str, size_type __pos = `0`) const
2779	_GLIBCXX_NOEXCEPT
2780	{ return this->find_first_of(__str.data(), __pos, __str.size()); }
2781
2782	#if __cplusplus >= 201703L
2783	/**
2784	* @brief Find position of a character of a string_view.
2785	* @param __svt An object convertible to string_view containing
2786	* characters to locate.
2787	* @param __pos Index of character to search from (default 0).
2788	* @return Index of first occurrence.
2789	*/
2790	template<typename _Tp>
2791	_GLIBCXX20_CONSTEXPR
2792	_If_sv<_Tp, size_type>
2793	find_first_of(const _Tp& __svt, size_type __pos = `0`) const
2794	noexcept(is_same<_Tp, __sv_type>::value)
2795	{
2796	__sv_type __sv = __svt;
2797	return this->find_first_of(__sv.data(), __pos, __sv.size());
2798	}
2799	#endif // C++17
2800
2801	/**
2802	* @brief Find position of a character of C substring.
2803	* @param __s String containing characters to locate.
2804	* @param __pos Index of character to search from.
2805	* @param __n Number of characters from s to search for.
2806	* @return Index of first occurrence.
2807	*
2808	* Starting from @a __pos, searches forward for one of the
2809	* first @a __n characters of @a __s within this string. If
2810	* found, returns the index where it was found. If not found,
2811	* returns npos.
2812	*/
2813	_GLIBCXX20_CONSTEXPR
2814	size_type
2815	find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
2816	_GLIBCXX_NOEXCEPT;
2817
2818	/**
2819	* @brief Find position of a character of C string.
2820	* @param __s String containing characters to locate.
2821	* @param __pos Index of character to search from (default 0).
2822	* @return Index of first occurrence.
2823	*
2824	* Starting from @a __pos, searches forward for one of the
2825	* characters of @a __s within this string. If found, returns
2826	* the index where it was found. If not found, returns npos.
2827	*/
2828	_GLIBCXX20_CONSTEXPR
2829	size_type
2830	find_first_of(const _CharT* __s, size_type __pos = `0`) const
2831	_GLIBCXX_NOEXCEPT
2832	{
2833	__glibcxx_requires_string(__s);
2834	return this->find_first_of(__s, __pos, traits_type::length(__s));
2835	}
2836
2837	/**
2838	* @brief Find position of a character.
2839	* @param __c Character to locate.
2840	* @param __pos Index of character to search from (default 0).
2841	* @return Index of first occurrence.
2842	*
2843	* Starting from @a __pos, searches forward for the character
2844	* @a __c within this string. If found, returns the index
2845	* where it was found. If not found, returns npos.
2846	*
2847	* Note: equivalent to find(__c, __pos).
2848	*/
2849	_GLIBCXX20_CONSTEXPR
2850	size_type
2851	find_first_of(_CharT __c, size_type __pos = `0`) const _GLIBCXX_NOEXCEPT
2852	{ return this->find(__c, __pos); }
2853
2854	/**
2855	* @brief Find last position of a character of string.
2856	* @param __str String containing characters to locate.
2857	* @param __pos Index of character to search back from (default end).
2858	* @return Index of last occurrence.
2859	*
2860	* Starting from @a __pos, searches backward for one of the
2861	* characters of @a __str within this string. If found,
2862	* returns the index where it was found. If not found, returns
2863	* npos.
2864	*/
2865	_GLIBCXX20_CONSTEXPR
2866	size_type
2867	find_last_of(const basic_string& __str, size_type __pos = npos) const
2868	_GLIBCXX_NOEXCEPT
2869	{ return this->find_last_of(__str.data(), __pos, __str.size()); }
2870
2871	#if __cplusplus >= 201703L
2872	/**
2873	* @brief Find last position of a character of string.
2874	* @param __svt An object convertible to string_view containing
2875	* characters to locate.
2876	* @param __pos Index of character to search back from (default end).
2877	* @return Index of last occurrence.
2878	*/
2879	template<typename _Tp>
2880	_GLIBCXX20_CONSTEXPR
2881	_If_sv<_Tp, size_type>
2882	find_last_of(const _Tp& __svt, size_type __pos = npos) const
2883	noexcept(is_same<_Tp, __sv_type>::value)
2884	{
2885	__sv_type __sv = __svt;
2886	return this->find_last_of(__sv.data(), __pos, __sv.size());
2887	}
2888	#endif // C++17
2889
2890	/**
2891	* @brief Find last position of a character of C substring.
2892	* @param __s C string containing characters to locate.
2893	* @param __pos Index of character to search back from.
2894	* @param __n Number of characters from s to search for.
2895	* @return Index of last occurrence.
2896	*
2897	* Starting from @a __pos, searches backward for one of the
2898	* first @a __n characters of @a __s within this string. If
2899	* found, returns the index where it was found. If not found,
2900	* returns npos.
2901	*/
2902	_GLIBCXX20_CONSTEXPR
2903	size_type
2904	find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
2905	_GLIBCXX_NOEXCEPT;
2906
2907	/**
2908	* @brief Find last position of a character of C string.
2909	* @param __s C string containing characters to locate.
2910	* @param __pos Index of character to search back from (default end).
2911	* @return Index of last occurrence.
2912	*
2913	* Starting from @a __pos, searches backward for one of the
2914	* characters of @a __s within this string. If found, returns
2915	* the index where it was found. If not found, returns npos.
2916	*/
2917	_GLIBCXX20_CONSTEXPR
2918	size_type
2919	find_last_of(const _CharT* __s, size_type __pos = npos) const
2920	_GLIBCXX_NOEXCEPT
2921	{
2922	__glibcxx_requires_string(__s);
2923	return this->find_last_of(__s, __pos, traits_type::length(__s));
2924	}
2925
2926	/**
2927	* @brief Find last position of a character.
2928	* @param __c Character to locate.
2929	* @param __pos Index of character to search back from (default end).
2930	* @return Index of last occurrence.
2931	*
2932	* Starting from @a __pos, searches backward for @a __c within
2933	* this string. If found, returns the index where it was
2934	* found. If not found, returns npos.
2935	*
2936	* Note: equivalent to rfind(__c, __pos).
2937	*/
2938	_GLIBCXX20_CONSTEXPR
2939	size_type
2940	find_last_of(_CharT __c, size_type __pos = npos) const _GLIBCXX_NOEXCEPT
2941	{ return this->rfind(__c, __pos); }
2942
2943	/**
2944	* @brief Find position of a character not in string.
2945	* @param __str String containing characters to avoid.
2946	* @param __pos Index of character to search from (default 0).
2947	* @return Index of first occurrence.
2948	*
2949	* Starting from @a __pos, searches forward for a character not contained
2950	* in @a __str within this string. If found, returns the index where it
2951	* was found. If not found, returns npos.
2952	*/
2953	_GLIBCXX20_CONSTEXPR
2954	size_type
2955	find_first_not_of(const basic_string& __str, size_type __pos = `0`) const
2956	_GLIBCXX_NOEXCEPT
2957	{ return this->find_first_not_of(__str.data(), __pos, __str.size()); }
2958
2959	#if __cplusplus >= 201703L
2960	/**
2961	* @brief Find position of a character not in a string_view.
2962	* @param __svt A object convertible to string_view containing
2963	* characters to avoid.
2964	* @param __pos Index of character to search from (default 0).
2965	* @return Index of first occurrence.
2966	*/
2967	template<typename _Tp>
2968	_If_sv<_Tp, size_type>
2969	_GLIBCXX20_CONSTEXPR
2970	find_first_not_of(const _Tp& __svt, size_type __pos = `0`) const
2971	noexcept(is_same<_Tp, __sv_type>::value)
2972	{
2973	__sv_type __sv = __svt;
2974	return this->find_first_not_of(__sv.data(), __pos, __sv.size());
2975	}
2976	#endif // C++17
2977
2978	/**
2979	* @brief Find position of a character not in C substring.
2980	* @param __s C string containing characters to avoid.
2981	* @param __pos Index of character to search from.
2982	* @param __n Number of characters from __s to consider.
2983	* @return Index of first occurrence.
2984	*
2985	* Starting from @a __pos, searches forward for a character not
2986	* contained in the first @a __n characters of @a __s within
2987	* this string. If found, returns the index where it was
2988	* found. If not found, returns npos.
2989	*/
2990	_GLIBCXX20_CONSTEXPR
2991	size_type
2992	find_first_not_of(const _CharT* __s, size_type __pos,
2993	size_type __n) const _GLIBCXX_NOEXCEPT;
2994
2995	/**
2996	* @brief Find position of a character not in C string.
2997	* @param __s C string containing characters to avoid.
2998	* @param __pos Index of character to search from (default 0).
2999	* @return Index of first occurrence.
3000	*
3001	* Starting from @a __pos, searches forward for a character not
3002	* contained in @a __s within this string. If found, returns
3003	* the index where it was found. If not found, returns npos.
3004	*/
3005	_GLIBCXX20_CONSTEXPR
3006	size_type
3007	find_first_not_of(const _CharT* __s, size_type __pos = `0`) const
3008	_GLIBCXX_NOEXCEPT
3009	{
3010	__glibcxx_requires_string(__s);
3011	return this->find_first_not_of(__s, __pos, traits_type::length(__s));
3012	}
3013
3014	/**
3015	* @brief Find position of a different character.
3016	* @param __c Character to avoid.
3017	* @param __pos Index of character to search from (default 0).
3018	* @return Index of first occurrence.
3019	*
3020	* Starting from @a __pos, searches forward for a character
3021	* other than @a __c within this string. If found, returns the
3022	* index where it was found. If not found, returns npos.
3023	*/
3024	_GLIBCXX20_CONSTEXPR
3025	size_type
3026	find_first_not_of(_CharT __c, size_type __pos = `0`) const
3027	_GLIBCXX_NOEXCEPT;
3028
3029	/**
3030	* @brief Find last position of a character not in string.
3031	* @param __str String containing characters to avoid.
3032	* @param __pos Index of character to search back from (default end).
3033	* @return Index of last occurrence.
3034	*
3035	* Starting from @a __pos, searches backward for a character
3036	* not contained in @a __str within this string. If found,
3037	* returns the index where it was found. If not found, returns
3038	* npos.
3039	*/
3040	_GLIBCXX20_CONSTEXPR
3041	size_type
3042	find_last_not_of(const basic_string& __str, size_type __pos = npos) const
3043	_GLIBCXX_NOEXCEPT
3044	{ return this->find_last_not_of(__str.data(), __pos, __str.size()); }
3045
3046	#if __cplusplus >= 201703L
3047	/**
3048	* @brief Find last position of a character not in a string_view.
3049	* @param __svt An object convertible to string_view containing
3050	* characters to avoid.
3051	* @param __pos Index of character to search back from (default end).
3052	* @return Index of last occurrence.
3053	*/
3054	template<typename _Tp>
3055	_GLIBCXX20_CONSTEXPR
3056	_If_sv<_Tp, size_type>
3057	find_last_not_of(const _Tp& __svt, size_type __pos = npos) const
3058	noexcept(is_same<_Tp, __sv_type>::value)
3059	{
3060	__sv_type __sv = __svt;
3061	return this->find_last_not_of(__sv.data(), __pos, __sv.size());
3062	}
3063	#endif // C++17
3064
3065	/**
3066	* @brief Find last position of a character not in C substring.
3067	* @param __s C string containing characters to avoid.
3068	* @param __pos Index of character to search back from.
3069	* @param __n Number of characters from s to consider.
3070	* @return Index of last occurrence.
3071	*
3072	* Starting from @a __pos, searches backward for a character not
3073	* contained in the first @a __n characters of @a __s within this string.
3074	* If found, returns the index where it was found. If not found,
3075	* returns npos.
3076	*/
3077	_GLIBCXX20_CONSTEXPR
3078	size_type
3079	find_last_not_of(const _CharT* __s, size_type __pos,
3080	size_type __n) const _GLIBCXX_NOEXCEPT;
3081	/**
3082	* @brief Find last position of a character not in C string.
3083	* @param __s C string containing characters to avoid.
3084	* @param __pos Index of character to search back from (default end).
3085	* @return Index of last occurrence.
3086	*
3087	* Starting from @a __pos, searches backward for a character
3088	* not contained in @a __s within this string. If found,
3089	* returns the index where it was found. If not found, returns
3090	* npos.
3091	*/
3092	_GLIBCXX20_CONSTEXPR
3093	size_type
3094	find_last_not_of(const _CharT* __s, size_type __pos = npos) const
3095	_GLIBCXX_NOEXCEPT
3096	{
3097	__glibcxx_requires_string(__s);
3098	return this->find_last_not_of(__s, __pos, traits_type::length(__s));
3099	}
3100
3101	/**
3102	* @brief Find last position of a different character.
3103	* @param __c Character to avoid.
3104	* @param __pos Index of character to search back from (default end).
3105	* @return Index of last occurrence.
3106	*
3107	* Starting from @a __pos, searches backward for a character other than
3108	* @a __c within this string. If found, returns the index where it was
3109	* found. If not found, returns npos.
3110	*/
3111	_GLIBCXX20_CONSTEXPR
3112	size_type
3113	find_last_not_of(_CharT __c, size_type __pos = npos) const
3114	_GLIBCXX_NOEXCEPT;
3115
3116	/**
3117	* @brief Get a substring.
3118	* @param __pos Index of first character (default 0).
3119	* @param __n Number of characters in substring (default remainder).
3120	* @return The new string.
3121	* @throw std::out_of_range If __pos > size().
3122	*
3123	* Construct and return a new string using the @a __n
3124	* characters starting at @a __pos. If the string is too
3125	* short, use the remainder of the characters. If @a __pos is
3126	* beyond the end of the string, out_of_range is thrown.
3127	*/
3128	_GLIBCXX20_CONSTEXPR
3129	basic_string
3130	substr(size_type __pos = `0`, size_type __n = npos) const
3131	{ return basic_string(*this,
3132	_M_check(__pos, "basic_string::substr"), __n); }
3133
3134	/**
3135	* @brief Compare to a string.
3136	* @param __str String to compare against.
3137	* @return Integer < 0, 0, or > 0.
3138	*
3139	* Returns an integer < 0 if this string is ordered before @a
3140	* __str, 0 if their values are equivalent, or > 0 if this
3141	* string is ordered after @a __str. Determines the effective
3142	* length rlen of the strings to compare as the smallest of
3143	* size() and str.size(). The function then compares the two
3144	* strings by calling traits::compare(data(), str.data(),rlen).
3145	* If the result of the comparison is nonzero returns it,
3146	* otherwise the shorter one is ordered first.
3147	*/
3148	_GLIBCXX20_CONSTEXPR
3149	int
3150	compare(const basic_string& __str) const
3151	{
3152	const size_type __size = this->size();
3153	const size_type __osize = __str.size();
3154	const size_type __len = std::min(__size, __osize);
3155
3156	int __r = traits_type::compare(_M_data(), __str.data(), __len);
3157	if (!__r)
3158	__r = _S_compare(__size, __osize);
3159	return __r;
3160	}
3161
3162	#if __cplusplus >= 201703L
3163	/**
3164	* @brief Compare to a string_view.
3165	* @param __svt An object convertible to string_view to compare against.
3166	* @return Integer < 0, 0, or > 0.
3167	*/
3168	template<typename _Tp>
3169	_GLIBCXX20_CONSTEXPR
3170	_If_sv<_Tp, int>
3171	compare(const _Tp& __svt) const
3172	noexcept(is_same<_Tp, __sv_type>::value)
3173	{
3174	__sv_type __sv = __svt;
3175	const size_type __size = this->size();
3176	const size_type __osize = __sv.size();
3177	const size_type __len = std::min(__size, __osize);
3178
3179	int __r = traits_type::compare(_M_data(), __sv.data(), __len);
3180	if (!__r)
3181	__r = _S_compare(__size, __osize);
3182	return __r;
3183	}
3184
3185	/**
3186	* @brief Compare to a string_view.
3187	* @param __pos A position in the string to start comparing from.
3188	* @param __n The number of characters to compare.
3189	* @param __svt An object convertible to string_view to compare
3190	* against.
3191	* @return Integer < 0, 0, or > 0.
3192	*/
3193	template<typename _Tp>
3194	_GLIBCXX20_CONSTEXPR
3195	_If_sv<_Tp, int>
3196	compare(size_type __pos, size_type __n, const _Tp& __svt) const
3197	noexcept(is_same<_Tp, __sv_type>::value)
3198	{
3199	__sv_type __sv = __svt;
3200	return __sv_type(*this).substr(__pos, __n).compare(__sv);
3201	}
3202
3203	/**
3204	* @brief Compare to a string_view.
3205	* @param __pos1 A position in the string to start comparing from.
3206	* @param __n1 The number of characters to compare.
3207	* @param __svt An object convertible to string_view to compare
3208	* against.
3209	* @param __pos2 A position in the string_view to start comparing from.
3210	* @param __n2 The number of characters to compare.
3211	* @return Integer < 0, 0, or > 0.
3212	*/
3213	template<typename _Tp>
3214	_GLIBCXX20_CONSTEXPR
3215	_If_sv<_Tp, int>
3216	compare(size_type __pos1, size_type __n1, const _Tp& __svt,
3217	size_type __pos2, size_type __n2 = npos) const
3218	noexcept(is_same<_Tp, __sv_type>::value)
3219	{
3220	__sv_type __sv = __svt;
3221	return __sv_type(*this)
3222	.substr(__pos1, __n1).compare(__sv.substr(__pos2, __n2));
3223	}
3224	#endif // C++17
3225
3226	/**
3227	* @brief Compare substring to a string.
3228	* @param __pos Index of first character of substring.
3229	* @param __n Number of characters in substring.
3230	* @param __str String to compare against.
3231	* @return Integer < 0, 0, or > 0.
3232	*
3233	* Form the substring of this string from the @a __n characters
3234	* starting at @a __pos. Returns an integer < 0 if the
3235	* substring is ordered before @a __str, 0 if their values are
3236	* equivalent, or > 0 if the substring is ordered after @a
3237	* __str. Determines the effective length rlen of the strings
3238	* to compare as the smallest of the length of the substring
3239	* and @a __str.size(). The function then compares the two
3240	* strings by calling
3241	* traits::compare(substring.data(),str.data(),rlen). If the
3242	* result of the comparison is nonzero returns it, otherwise
3243	* the shorter one is ordered first.
3244	*/
3245	_GLIBCXX20_CONSTEXPR
3246	int
3247	compare(size_type __pos, size_type __n, const basic_string& __str) const;
3248
3249	/**
3250	* @brief Compare substring to a substring.
3251	* @param __pos1 Index of first character of substring.
3252	* @param __n1 Number of characters in substring.
3253	* @param __str String to compare against.
3254	* @param __pos2 Index of first character of substring of str.
3255	* @param __n2 Number of characters in substring of str.
3256	* @return Integer < 0, 0, or > 0.
3257	*
3258	* Form the substring of this string from the @a __n1
3259	* characters starting at @a __pos1. Form the substring of @a
3260	* __str from the @a __n2 characters starting at @a __pos2.
3261	* Returns an integer < 0 if this substring is ordered before
3262	* the substring of @a __str, 0 if their values are equivalent,
3263	* or > 0 if this substring is ordered after the substring of
3264	* @a __str. Determines the effective length rlen of the
3265	* strings to compare as the smallest of the lengths of the
3266	* substrings. The function then compares the two strings by
3267	* calling
3268	* traits::compare(substring.data(),str.substr(pos2,n2).data(),rlen).
3269	* If the result of the comparison is nonzero returns it,
3270	* otherwise the shorter one is ordered first.
3271	*/
3272	_GLIBCXX20_CONSTEXPR
3273	int
3274	compare(size_type __pos1, size_type __n1, const basic_string& __str,
3275	size_type __pos2, size_type __n2 = npos) const;
3276
3277	/**
3278	* @brief Compare to a C string.
3279	* @param __s C string to compare against.
3280	* @return Integer < 0, 0, or > 0.
3281	*
3282	* Returns an integer < 0 if this string is ordered before @a __s, 0 if
3283	* their values are equivalent, or > 0 if this string is ordered after
3284	* @a __s. Determines the effective length rlen of the strings to
3285	* compare as the smallest of size() and the length of a string
3286	* constructed from @a __s. The function then compares the two strings
3287	* by calling traits::compare(data(),s,rlen). If the result of the
3288	* comparison is nonzero returns it, otherwise the shorter one is
3289	* ordered first.
3290	*/
3291	_GLIBCXX20_CONSTEXPR
3292	int
3293	compare(const _CharT* __s) const _GLIBCXX_NOEXCEPT;
3294
3295	// _GLIBCXX_RESOLVE_LIB_DEFECTS
3296	// 5 String::compare specification questionable
3297	/**
3298	* @brief Compare substring to a C string.
3299	* @param __pos Index of first character of substring.
3300	* @param __n1 Number of characters in substring.
3301	* @param __s C string to compare against.
3302	* @return Integer < 0, 0, or > 0.
3303	*
3304	* Form the substring of this string from the @a __n1
3305	* characters starting at @a pos. Returns an integer < 0 if
3306	* the substring is ordered before @a __s, 0 if their values
3307	* are equivalent, or > 0 if the substring is ordered after @a
3308	* __s. Determines the effective length rlen of the strings to
3309	* compare as the smallest of the length of the substring and
3310	* the length of a string constructed from @a __s. The
3311	* function then compares the two string by calling
3312	* traits::compare(substring.data(),__s,rlen). If the result of
3313	* the comparison is nonzero returns it, otherwise the shorter
3314	* one is ordered first.
3315	*/
3316	_GLIBCXX20_CONSTEXPR
3317	int
3318	compare(size_type __pos, size_type __n1, const _CharT* __s) const;
3319
3320	/**
3321	* @brief Compare substring against a character %array.
3322	* @param __pos Index of first character of substring.
3323	* @param __n1 Number of characters in substring.
3324	* @param __s character %array to compare against.
3325	* @param __n2 Number of characters of s.
3326	* @return Integer < 0, 0, or > 0.
3327	*
3328	* Form the substring of this string from the @a __n1
3329	* characters starting at @a __pos. Form a string from the
3330	* first @a __n2 characters of @a __s. Returns an integer < 0
3331	* if this substring is ordered before the string from @a __s,
3332	* 0 if their values are equivalent, or > 0 if this substring
3333	* is ordered after the string from @a __s. Determines the
3334	* effective length rlen of the strings to compare as the
3335	* smallest of the length of the substring and @a __n2. The
3336	* function then compares the two strings by calling
3337	* traits::compare(substring.data(),s,rlen). If the result of
3338	* the comparison is nonzero returns it, otherwise the shorter
3339	* one is ordered first.
3340	*
3341	* NB: s must have at least n2 characters, '\\0' has
3342	* no special meaning.
3343	*/
3344	_GLIBCXX20_CONSTEXPR
3345	int
3346	compare(size_type __pos, size_type __n1, const _CharT* __s,
3347	size_type __n2) const;
3348
3349	#if __cplusplus >= 202002L
3350	constexpr bool
3351	starts_with(basic_string_view<_CharT, _Traits> __x) const noexcept
3352	{ return __sv_type(this->data(), this->size()).starts_with(__x); }
3353
3354	constexpr bool
3355	starts_with(_CharT __x) const noexcept
3356	{ return __sv_type(this->data(), this->size()).starts_with(__x); }
3357
3358	constexpr bool
3359	starts_with(const _CharT* __x) const noexcept
3360	{ return __sv_type(this->data(), this->size()).starts_with(__x); }
3361
3362	constexpr bool
3363	ends_with(basic_string_view<_CharT, _Traits> __x) const noexcept
3364	{ return __sv_type(this->data(), this->size()).ends_with(__x); }
3365
3366	constexpr bool
3367	ends_with(_CharT __x) const noexcept
3368	{ return __sv_type(this->data(), this->size()).ends_with(__x); }
3369
3370	constexpr bool
3371	ends_with(const _CharT* __x) const noexcept
3372	{ return __sv_type(this->data(), this->size()).ends_with(__x); }
3373	#endif // C++20
3374
3375	#if __cplusplus > 202002L
3376	constexpr bool
3377	contains(basic_string_view<_CharT, _Traits> __x) const noexcept
3378	{ return __sv_type(this->data(), this->size()).contains(__x); }
3379
3380	constexpr bool
3381	contains(_CharT __x) const noexcept
3382	{ return __sv_type(this->data(), this->size()).contains(__x); }
3383
3384	constexpr bool
3385	contains(const _CharT* __x) const noexcept
3386	{ return __sv_type(this->data(), this->size()).contains(__x); }
3387	#endif // C++23
3388
3389	// Allow basic_stringbuf::__xfer_bufptrs to call _M_length:
3390	template<typename, typename, typename> friend class basic_stringbuf;
3391	};
3392	_GLIBCXX_END_NAMESPACE_CXX11
3393	_GLIBCXX_END_NAMESPACE_VERSION
3394	} // namespace std
3395	#endif // _GLIBCXX_USE_CXX11_ABI
3396
3397	namespace std _GLIBCXX_VISIBILITY(default)
3398	{
3399	_GLIBCXX_BEGIN_NAMESPACE_VERSION
3400
3401	#if __cpp_deduction_guides >= 201606
3402	_GLIBCXX_BEGIN_NAMESPACE_CXX11
3403	template<typename _InputIterator, typename _CharT
3404	= typename iterator_traits<_InputIterator>::value_type,
3405	typename _Allocator = allocator<_CharT>,
3406	typename = _RequireInputIter<_InputIterator>,
3407	typename = _RequireAllocator<_Allocator>>
3408	basic_string(_InputIterator, _InputIterator, _Allocator = _Allocator())
3409	-> basic_string<_CharT, char_traits<_CharT>, _Allocator>;
3410
3411	// _GLIBCXX_RESOLVE_LIB_DEFECTS
3412	// 3075. basic_string needs deduction guides from basic_string_view
3413	template<typename _CharT, typename _Traits,
3414	typename _Allocator = allocator<_CharT>,
3415	typename = _RequireAllocator<_Allocator>>
3416	basic_string(basic_string_view<_CharT, _Traits>, const _Allocator& = _Allocator())
3417	-> basic_string<_CharT, _Traits, _Allocator>;
3418
3419	template<typename _CharT, typename _Traits,
3420	typename _Allocator = allocator<_CharT>,
3421	typename = _RequireAllocator<_Allocator>>
3422	basic_string(basic_string_view<_CharT, _Traits>,
3423	typename basic_string<_CharT, _Traits, _Allocator>::size_type,
3424	typename basic_string<_CharT, _Traits, _Allocator>::size_type,
3425	const _Allocator& = _Allocator())
3426	-> basic_string<_CharT, _Traits, _Allocator>;
3427	_GLIBCXX_END_NAMESPACE_CXX11
3428	#endif
3429
3430	// operator+
3431	/**
3432	* @brief Concatenate two strings.
3433	* @param __lhs First string.
3434	* @param __rhs Last string.
3435	* @return New string with value of @a __lhs followed by @a __rhs.
3436	*/
3437	template<typename _CharT, typename _Traits, typename _Alloc>
3438	_GLIBCXX20_CONSTEXPR
3439	basic_string<_CharT, _Traits, _Alloc>
3440	operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3441	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3442	{
3443	basic_string<_CharT, _Traits, _Alloc> __str(__lhs);
3444	__str.append(__rhs);
3445	return __str;
3446	}
3447
3448	/**
3449	* @brief Concatenate C string and string.
3450	* @param __lhs First string.
3451	* @param __rhs Last string.
3452	* @return New string with value of @a __lhs followed by @a __rhs.
3453	*/
3454	template<typename _CharT, typename _Traits, typename _Alloc>
3455	_GLIBCXX20_CONSTEXPR
3456	basic_string<_CharT,_Traits,_Alloc>
3457	operator+(const _CharT* __lhs,
3458	const basic_string<_CharT,_Traits,_Alloc>& __rhs);
3459
3460	/**
3461	* @brief Concatenate character and string.
3462	* @param __lhs First string.
3463	* @param __rhs Last string.
3464	* @return New string with @a __lhs followed by @a __rhs.
3465	*/
3466	template<typename _CharT, typename _Traits, typename _Alloc>
3467	_GLIBCXX20_CONSTEXPR
3468	basic_string<_CharT,_Traits,_Alloc>
3469	operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs);
3470
3471	/**
3472	* @brief Concatenate string and C string.
3473	* @param __lhs First string.
3474	* @param __rhs Last string.
3475	* @return New string with @a __lhs followed by @a __rhs.
3476	*/
3477	template<typename _CharT, typename _Traits, typename _Alloc>
3478	_GLIBCXX20_CONSTEXPR
3479	inline basic_string<_CharT, _Traits, _Alloc>
3480	operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3481	const _CharT* __rhs)
3482	{
3483	basic_string<_CharT, _Traits, _Alloc> __str(__lhs);
3484	__str.append(__rhs);
3485	return __str;
3486	}
3487
3488	/**
3489	* @brief Concatenate string and character.
3490	* @param __lhs First string.
3491	* @param __rhs Last string.
3492	* @return New string with @a __lhs followed by @a __rhs.
3493	*/
3494	template<typename _CharT, typename _Traits, typename _Alloc>
3495	_GLIBCXX20_CONSTEXPR
3496	inline basic_string<_CharT, _Traits, _Alloc>
3497	operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
3498	{
3499	typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
3500	typedef typename __string_type::size_type __size_type;
3501	__string_type __str(__lhs);
3502	__str.append(__size_type(`1`), __rhs);
3503	return __str;
3504	}
3505
3506	#if __cplusplus >= 201103L
3507	template<typename _CharT, typename _Traits, typename _Alloc>
3508	_GLIBCXX20_CONSTEXPR
3509	inline basic_string<_CharT, _Traits, _Alloc>
3510	operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
3511	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3512	{ return std::move(__lhs.append(__rhs)); }
3513
3514	template<typename _CharT, typename _Traits, typename _Alloc>
3515	_GLIBCXX20_CONSTEXPR
3516	inline basic_string<_CharT, _Traits, _Alloc>
3517	operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3518	basic_string<_CharT, _Traits, _Alloc>&& __rhs)
3519	{ return std::move(__rhs.insert(`0`, __lhs)); }
3520
3521	template<typename _CharT, typename _Traits, typename _Alloc>
3522	_GLIBCXX20_CONSTEXPR
3523	inline basic_string<_CharT, _Traits, _Alloc>
3524	operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
3525	basic_string<_CharT, _Traits, _Alloc>&& __rhs)
3526	{
3527	#if _GLIBCXX_USE_CXX11_ABI
3528	using _Alloc_traits = allocator_traits<_Alloc>;
3529	bool __use_rhs = false;
3530	if _GLIBCXX17_CONSTEXPR (typename _Alloc_traits::is_always_equal{})
3531	__use_rhs = true;
3532	else if (__lhs.get_allocator() == __rhs.get_allocator())
3533	__use_rhs = true;
3534	if (__use_rhs)
3535	#endif
3536	{
3537	const auto __size = __lhs.size() + __rhs.size();
3538	if (__size > __lhs.capacity() && __size <= __rhs.capacity())
3539	return std::move(__rhs.insert(`0`, __lhs));
3540	}
3541	return std::move(__lhs.append(__rhs));
3542	}
3543
3544	template<typename _CharT, typename _Traits, typename _Alloc>
3545	_GLIBCXX20_CONSTEXPR
3546	inline basic_string<_CharT, _Traits, _Alloc>
3547	operator+(const _CharT* __lhs,
3548	basic_string<_CharT, _Traits, _Alloc>&& __rhs)
3549	{ return std::move(__rhs.insert(`0`, __lhs)); }
3550
3551	template<typename _CharT, typename _Traits, typename _Alloc>
3552	_GLIBCXX20_CONSTEXPR
3553	inline basic_string<_CharT, _Traits, _Alloc>
3554	operator+(_CharT __lhs,
3555	basic_string<_CharT, _Traits, _Alloc>&& __rhs)
3556	{ return std::move(__rhs.insert(`0`, `1`, __lhs)); }
3557
3558	template<typename _CharT, typename _Traits, typename _Alloc>
3559	_GLIBCXX20_CONSTEXPR
3560	inline basic_string<_CharT, _Traits, _Alloc>
3561	operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
3562	const _CharT* __rhs)
3563	{ return std::move(__lhs.append(__rhs)); }
3564
3565	template<typename _CharT, typename _Traits, typename _Alloc>
3566	_GLIBCXX20_CONSTEXPR
3567	inline basic_string<_CharT, _Traits, _Alloc>
3568	operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
3569	_CharT __rhs)
3570	{ return std::move(__lhs.append(`1`, __rhs)); }
3571	#endif
3572
3573	// operator ==
3574	/**
3575	* @brief Test equivalence of two strings.
3576	* @param __lhs First string.
3577	* @param __rhs Second string.
3578	* @return True if @a __lhs.compare(@a __rhs) == 0. False otherwise.
3579	*/
3580	template<typename _CharT, typename _Traits, typename _Alloc>
3581	_GLIBCXX20_CONSTEXPR
3582	inline bool
3583	operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3584	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3585	_GLIBCXX_NOEXCEPT
3586	{ return __lhs.compare(__rhs) == `0`; }
3587
3588	template<typename _CharT>
3589	_GLIBCXX20_CONSTEXPR
3590	inline
3591	typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value, bool>::__type
3592	operator==(const basic_string<_CharT>& __lhs,
3593	const basic_string<_CharT>& __rhs) _GLIBCXX_NOEXCEPT
3594	{ return (__lhs.size() == __rhs.size()
3595	&& !std::char_traits<_CharT>::compare(__lhs.data(), __rhs.data(),
3596	__lhs.size())); }
3597
3598	/**
3599	* @brief Test equivalence of string and C string.
3600	* @param __lhs String.
3601	* @param __rhs C string.
3602	* @return True if @a __lhs.compare(@a __rhs) == 0. False otherwise.
3603	*/
3604	template<typename _CharT, typename _Traits, typename _Alloc>
3605	_GLIBCXX20_CONSTEXPR
3606	inline bool
3607	operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3608	const _CharT* __rhs)
3609	{ return __lhs.compare(__rhs) == `0`; }
3610
3611	#if __cpp_lib_three_way_comparison
3612	/**
3613	* @brief Three-way comparison of a string and a C string.
3614	* @param __lhs A string.
3615	* @param __rhs A null-terminated string.
3616	* @return A value indicating whether `__lhs` is less than, equal to,
3617	* greater than, or incomparable with `__rhs`.
3618	*/
3619	template<typename _CharT, typename _Traits, typename _Alloc>
3620	constexpr auto
3621	operator<=>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3622	const basic_string<_CharT, _Traits, _Alloc>& __rhs) noexcept
3623	-> decltype(__detail::__char_traits_cmp_cat<_Traits>(`0`))
3624	{ return __detail::__char_traits_cmp_cat<_Traits>(__lhs.compare(__rhs)); }
3625
3626	/**
3627	* @brief Three-way comparison of a string and a C string.
3628	* @param __lhs A string.
3629	* @param __rhs A null-terminated string.
3630	* @return A value indicating whether `__lhs` is less than, equal to,
3631	* greater than, or incomparable with `__rhs`.
3632	*/
3633	template<typename _CharT, typename _Traits, typename _Alloc>
3634	constexpr auto
3635	operator<=>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3636	const _CharT* __rhs) noexcept
3637	-> decltype(__detail::__char_traits_cmp_cat<_Traits>(`0`))
3638	{ return __detail::__char_traits_cmp_cat<_Traits>(__lhs.compare(__rhs)); }
3639	#else
3640	/**
3641	* @brief Test equivalence of C string and string.
3642	* @param __lhs C string.
3643	* @param __rhs String.
3644	* @return True if @a __rhs.compare(@a __lhs) == 0. False otherwise.
3645	*/
3646	template<typename _CharT, typename _Traits, typename _Alloc>
3647	inline bool
3648	operator==(const _CharT* __lhs,
3649	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3650	{ return __rhs.compare(__lhs) == `0`; }
3651
3652	// operator !=
3653	/**
3654	* @brief Test difference of two strings.
3655	* @param __lhs First string.
3656	* @param __rhs Second string.
3657	* @return True if @a __lhs.compare(@a __rhs) != 0. False otherwise.
3658	*/
3659	template<typename _CharT, typename _Traits, typename _Alloc>
3660	inline bool
3661	operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3662	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3663	_GLIBCXX_NOEXCEPT
3664	{ return !(__lhs == __rhs); }
3665
3666	/**
3667	* @brief Test difference of C string and string.
3668	* @param __lhs C string.
3669	* @param __rhs String.
3670	* @return True if @a __rhs.compare(@a __lhs) != 0. False otherwise.
3671	*/
3672	template<typename _CharT, typename _Traits, typename _Alloc>
3673	inline bool
3674	operator!=(const _CharT* __lhs,
3675	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3676	{ return !(__lhs == __rhs); }
3677
3678	/**
3679	* @brief Test difference of string and C string.
3680	* @param __lhs String.
3681	* @param __rhs C string.
3682	* @return True if @a __lhs.compare(@a __rhs) != 0. False otherwise.
3683	*/
3684	template<typename _CharT, typename _Traits, typename _Alloc>
3685	inline bool
3686	operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3687	const _CharT* __rhs)
3688	{ return !(__lhs == __rhs); }
3689
3690	// operator <
3691	/**
3692	* @brief Test if string precedes string.
3693	* @param __lhs First string.
3694	* @param __rhs Second string.
3695	* @return True if @a __lhs precedes @a __rhs. False otherwise.
3696	*/
3697	template<typename _CharT, typename _Traits, typename _Alloc>
3698	inline bool
3699	operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3700	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3701	_GLIBCXX_NOEXCEPT
3702	{ return __lhs.compare(__rhs) < `0`; }
3703
3704	/**
3705	* @brief Test if string precedes C string.
3706	* @param __lhs String.
3707	* @param __rhs C string.
3708	* @return True if @a __lhs precedes @a __rhs. False otherwise.
3709	*/
3710	template<typename _CharT, typename _Traits, typename _Alloc>
3711	inline bool
3712	operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3713	const _CharT* __rhs)
3714	{ return __lhs.compare(__rhs) < `0`; }
3715
3716	/**
3717	* @brief Test if C string precedes string.
3718	* @param __lhs C string.
3719	* @param __rhs String.
3720	* @return True if @a __lhs precedes @a __rhs. False otherwise.
3721	*/
3722	template<typename _CharT, typename _Traits, typename _Alloc>
3723	inline bool
3724	operator<(const _CharT* __lhs,
3725	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3726	{ return __rhs.compare(__lhs) > `0`; }
3727
3728	// operator >
3729	/**
3730	* @brief Test if string follows string.
3731	* @param __lhs First string.
3732	* @param __rhs Second string.
3733	* @return True if @a __lhs follows @a __rhs. False otherwise.
3734	*/
3735	template<typename _CharT, typename _Traits, typename _Alloc>
3736	inline bool
3737	operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3738	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3739	_GLIBCXX_NOEXCEPT
3740	{ return __lhs.compare(__rhs) > `0`; }
3741
3742	/**
3743	* @brief Test if string follows C string.
3744	* @param __lhs String.
3745	* @param __rhs C string.
3746	* @return True if @a __lhs follows @a __rhs. False otherwise.
3747	*/
3748	template<typename _CharT, typename _Traits, typename _Alloc>
3749	inline bool
3750	operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3751	const _CharT* __rhs)
3752	{ return __lhs.compare(__rhs) > `0`; }
3753
3754	/**
3755	* @brief Test if C string follows string.
3756	* @param __lhs C string.
3757	* @param __rhs String.
3758	* @return True if @a __lhs follows @a __rhs. False otherwise.
3759	*/
3760	template<typename _CharT, typename _Traits, typename _Alloc>
3761	inline bool
3762	operator>(const _CharT* __lhs,
3763	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3764	{ return __rhs.compare(__lhs) < `0`; }
3765
3766	// operator <=
3767	/**
3768	* @brief Test if string doesn't follow string.
3769	* @param __lhs First string.
3770	* @param __rhs Second string.
3771	* @return True if @a __lhs doesn't follow @a __rhs. False otherwise.
3772	*/
3773	template<typename _CharT, typename _Traits, typename _Alloc>
3774	inline bool
3775	operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3776	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3777	_GLIBCXX_NOEXCEPT
3778	{ return __lhs.compare(__rhs) <= `0`; }
3779
3780	/**
3781	* @brief Test if string doesn't follow C string.
3782	* @param __lhs String.
3783	* @param __rhs C string.
3784	* @return True if @a __lhs doesn't follow @a __rhs. False otherwise.
3785	*/
3786	template<typename _CharT, typename _Traits, typename _Alloc>
3787	inline bool
3788	operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3789	const _CharT* __rhs)
3790	{ return __lhs.compare(__rhs) <= `0`; }
3791
3792	/**
3793	* @brief Test if C string doesn't follow string.
3794	* @param __lhs C string.
3795	* @param __rhs String.
3796	* @return True if @a __lhs doesn't follow @a __rhs. False otherwise.
3797	*/
3798	template<typename _CharT, typename _Traits, typename _Alloc>
3799	inline bool
3800	operator<=(const _CharT* __lhs,
3801	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3802	{ return __rhs.compare(__lhs) >= `0`; }
3803
3804	// operator >=
3805	/**
3806	* @brief Test if string doesn't precede string.
3807	* @param __lhs First string.
3808	* @param __rhs Second string.
3809	* @return True if @a __lhs doesn't precede @a __rhs. False otherwise.
3810	*/
3811	template<typename _CharT, typename _Traits, typename _Alloc>
3812	inline bool
3813	operator>=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3814	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3815	_GLIBCXX_NOEXCEPT
3816	{ return __lhs.compare(__rhs) >= `0`; }
3817
3818	/**
3819	* @brief Test if string doesn't precede C string.
3820	* @param __lhs String.
3821	* @param __rhs C string.
3822	* @return True if @a __lhs doesn't precede @a __rhs. False otherwise.
3823	*/
3824	template<typename _CharT, typename _Traits, typename _Alloc>
3825	inline bool
3826	operator>=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
3827	const _CharT* __rhs)
3828	{ return __lhs.compare(__rhs) >= `0`; }
3829
3830	/**
3831	* @brief Test if C string doesn't precede string.
3832	* @param __lhs C string.
3833	* @param __rhs String.
3834	* @return True if @a __lhs doesn't precede @a __rhs. False otherwise.
3835	*/
3836	template<typename _CharT, typename _Traits, typename _Alloc>
3837	inline bool
3838	operator>=(const _CharT* __lhs,
3839	const basic_string<_CharT, _Traits, _Alloc>& __rhs)
3840	{ return __rhs.compare(__lhs) <= `0`; }
3841	#endif // three-way comparison
3842
3843	/**
3844	* @brief Swap contents of two strings.
3845	* @param __lhs First string.
3846	* @param __rhs Second string.
3847	*
3848	* Exchanges the contents of @a __lhs and @a __rhs in constant time.
3849	*/
3850	template<typename _CharT, typename _Traits, typename _Alloc>
3851	_GLIBCXX20_CONSTEXPR
3852	inline void
3853	swap(basic_string<_CharT, _Traits, _Alloc>& __lhs,
3854	basic_string<_CharT, _Traits, _Alloc>& __rhs)
3855	_GLIBCXX_NOEXCEPT_IF(noexcept(__lhs.swap(__rhs)))
3856	{ __lhs.swap(__rhs); }
3857
3858
3859	/**
3860	* @brief Read stream into a string.
3861	* @param __is Input stream.
3862	* @param __str Buffer to store into.
3863	* @return Reference to the input stream.
3864	*
3865	* Stores characters from @a __is into @a __str until whitespace is
3866	* found, the end of the stream is encountered, or str.max_size()
3867	* is reached. If is.width() is non-zero, that is the limit on the
3868	* number of characters stored into @a __str. Any previous
3869	* contents of @a __str are erased.
3870	*/
3871	template<typename _CharT, typename _Traits, typename _Alloc>
3872	basic_istream<_CharT, _Traits>&
3873	operator>>(basic_istream<_CharT, _Traits>& __is,
3874	basic_string<_CharT, _Traits, _Alloc>& __str);
3875
3876	template<>
3877	basic_istream<char>&
3878	operator>>(basic_istream<char>& __is, basic_string<char>& __str);
3879
3880	/**
3881	* @brief Write string to a stream.
3882	* @param __os Output stream.
3883	* @param __str String to write out.
3884	* @return Reference to the output stream.
3885	*
3886	* Output characters of @a __str into os following the same rules as for
3887	* writing a C string.
3888	*/
3889	template<typename _CharT, typename _Traits, typename _Alloc>
3890	inline basic_ostream<_CharT, _Traits>&
3891	operator<<(basic_ostream<_CharT, _Traits>& __os,
3892	const basic_string<_CharT, _Traits, _Alloc>& __str)
3893	{
3894	// _GLIBCXX_RESOLVE_LIB_DEFECTS
3895	// 586. string inserter not a formatted function
3896	return __ostream_insert(__os, __str.data(), __str.size());
3897	}
3898
3899	/**
3900	* @brief Read a line from stream into a string.
3901	* @param __is Input stream.
3902	* @param __str Buffer to store into.
3903	* @param __delim Character marking end of line.
3904	* @return Reference to the input stream.
3905	*
3906	* Stores characters from @a __is into @a __str until @a __delim is
3907	* found, the end of the stream is encountered, or str.max_size()
3908	* is reached. Any previous contents of @a __str are erased. If
3909	* @a __delim is encountered, it is extracted but not stored into
3910	* @a __str.
3911	*/
3912	template<typename _CharT, typename _Traits, typename _Alloc>
3913	basic_istream<_CharT, _Traits>&
3914	getline(basic_istream<_CharT, _Traits>& __is,
3915	basic_string<_CharT, _Traits, _Alloc>& __str, _CharT __delim);
3916
3917	/**
3918	* @brief Read a line from stream into a string.
3919	* @param __is Input stream.
3920	* @param __str Buffer to store into.
3921	* @return Reference to the input stream.
3922	*
3923	* Stores characters from is into @a __str until '\n' is
3924	* found, the end of the stream is encountered, or str.max_size()
3925	* is reached. Any previous contents of @a __str are erased. If
3926	* end of line is encountered, it is extracted but not stored into
3927	* @a __str.
3928	*/
3929	template<typename _CharT, typename _Traits, typename _Alloc>
3930	inline basic_istream<_CharT, _Traits>&
3931	getline(basic_istream<_CharT, _Traits>& __is,
3932	basic_string<_CharT, _Traits, _Alloc>& __str)
3933	{ return std::getline(__is, __str, __is.widen(`'\n'`)); }
3934
3935	#if __cplusplus >= 201103L
3936	/// Read a line from an rvalue stream into a string.
3937	template<typename _CharT, typename _Traits, typename _Alloc>
3938	inline basic_istream<_CharT, _Traits>&
3939	getline(basic_istream<_CharT, _Traits>&& __is,
3940	basic_string<_CharT, _Traits, _Alloc>& __str, _CharT __delim)
3941	{ return std::getline(__is, __str, __delim); }
3942
3943	/// Read a line from an rvalue stream into a string.
3944	template<typename _CharT, typename _Traits, typename _Alloc>
3945	inline basic_istream<_CharT, _Traits>&
3946	getline(basic_istream<_CharT, _Traits>&& __is,
3947	basic_string<_CharT, _Traits, _Alloc>& __str)
3948	{ return std::getline(__is, __str); }
3949	#endif
3950
3951	template<>
3952	basic_istream<char>&
3953	getline(basic_istream<char>& __in, basic_string<char>& __str,
3954	char __delim);
3955
3956	#ifdef _GLIBCXX_USE_WCHAR_T
3957	template<>
3958	basic_istream<wchar_t>&
3959	getline(basic_istream<wchar_t>& __in, basic_string<wchar_t>& __str,
3960	wchar_t __delim);
3961	#endif
3962
3963	_GLIBCXX_END_NAMESPACE_VERSION
3964	} // namespace
3965
3966	#if __cplusplus >= 201103L
3967
3968	#include <ext/string_conversions.h>
3969	#include <bits/charconv.h>
3970
3971	namespace std _GLIBCXX_VISIBILITY(default)
3972	{
3973	_GLIBCXX_BEGIN_NAMESPACE_VERSION
3974	_GLIBCXX_BEGIN_NAMESPACE_CXX11
3975
3976	#if _GLIBCXX_USE_C99_STDLIB
3977	// 21.4 Numeric Conversions [string.conversions].
3978	inline int
3979	stoi(const string& __str, size_t* __idx = `0`, int __base = `10`)
3980	{ return __gnu_cxx::__stoa<long, int>(&std::strtol, "stoi", __str.c_str(),
3981	__idx, __base); }
3982
3983	inline long
3984	stol(const string& __str, size_t* __idx = `0`, int __base = `10`)
3985	{ return __gnu_cxx::__stoa(&std::strtol, "stol", __str.c_str(),
3986	__idx, __base); }
3987
3988	inline unsigned long
3989	stoul(const string& __str, size_t* __idx = `0`, int __base = `10`)
3990	{ return __gnu_cxx::__stoa(&std::strtoul, "stoul", __str.c_str(),
3991	__idx, __base); }
3992
3993	inline long long
3994	stoll(const string& __str, size_t* __idx = `0`, int __base = `10`)
3995	{ return __gnu_cxx::__stoa(&std::strtoll, "stoll", __str.c_str(),
3996	__idx, __base); }
3997
3998	inline unsigned long long
3999	stoull(const string& __str, size_t* __idx = `0`, int __base = `10`)
4000	{ return __gnu_cxx::__stoa(&std::strtoull, "stoull", __str.c_str(),
4001	__idx, __base); }
4002
4003	// NB: strtof vs strtod.
4004	inline float
4005	stof(const string& __str, size_t* __idx = `0`)
4006	{ return __gnu_cxx::__stoa(&std::strtof, "stof", __str.c_str(), __idx); }
4007
4008	inline double
4009	stod(const string& __str, size_t* __idx = `0`)
4010	{ return __gnu_cxx::__stoa(&std::strtod, "stod", __str.c_str(), __idx); }
4011
4012	inline long double
4013	stold(const string& __str, size_t* __idx = `0`)
4014	{ return __gnu_cxx::__stoa(&std::strtold, "stold", __str.c_str(), __idx); }
4015	#endif // _GLIBCXX_USE_C99_STDLIB
4016
4017	// DR 1261. Insufficent overloads for to_string / to_wstring
4018
4019	inline string
4020	to_string(int __val)
4021	#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32
4022	noexcept // any 32-bit value fits in the SSO buffer
4023	#endif
4024	{
4025	const bool __neg = __val < `0`;
4026	const unsigned __uval = __neg ? (unsigned)~__val + `1u` : __val;
4027	const auto __len = __detail::__to_chars_len(__uval);
4028	string __str(__neg + __len, `'-'`);
4029	__detail::__to_chars_10_impl(&__str [__neg], __len, __uval);
4030	return __str;
4031	}
4032
4033	inline string
4034	to_string(unsigned __val)
4035	#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32
4036	noexcept // any 32-bit value fits in the SSO buffer
4037	#endif
4038	{
4039	string __str(__detail::__to_chars_len(__val), `'\0'`);
4040	__detail::__to_chars_10_impl(&__str [`0`], __str.size(), __val);
4041	return __str;
4042	}
4043
4044	inline string
4045	to_string(long __val)
4046	#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32
4047	noexcept // any 32-bit value fits in the SSO buffer
4048	#endif
4049	{
4050	const bool __neg = __val < `0`;
4051	const unsigned long __uval = __neg ? (unsigned long)~__val + `1ul` : __val;
4052	const auto __len = __detail::__to_chars_len(__uval);
4053	string __str(__neg + __len, `'-'`);
4054	__detail::__to_chars_10_impl(&__str [__neg], __len, __uval);
4055	return __str;
4056	}
4057
4058	inline string
4059	to_string(unsigned long __val)
4060	#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32
4061	noexcept // any 32-bit value fits in the SSO buffer
4062	#endif
4063	{
4064	string __str(__detail::__to_chars_len(__val), `'\0'`);
4065	__detail::__to_chars_10_impl(&__str [`0`], __str.size(), __val);
4066	return __str;
4067	}
4068
4069	inline string
4070	to_string(long long __val)
4071	{
4072	const bool __neg = __val < `0`;
4073	const unsigned long long __uval
4074	= __neg ? (unsigned long long)~__val + `1ull` : __val;
4075	const auto __len = __detail::__to_chars_len(__uval);
4076	string __str(__neg + __len, `'-'`);
4077	__detail::__to_chars_10_impl(&__str [__neg], __len, __uval);
4078	return __str;
4079	}
4080
4081	inline string
4082	to_string(unsigned long long __val)
4083	{
4084	string __str(__detail::__to_chars_len(__val), `'\0'`);
4085	__detail::__to_chars_10_impl(&__str [`0`], __str.size(), __val);
4086	return __str;
4087	}
4088
4089	#if _GLIBCXX_USE_C99_STDIO
4090	// NB: (v)snprintf vs sprintf.
4091
4092	inline string
4093	to_string(float __val)
4094	{
4095	const int __n =
4096	__gnu_cxx::__numeric_traits<float>::__max_exponent10 + `20`;
4097	return __gnu_cxx::__to_xstring<string>(&std::vsnprintf, __n,
4098	"%f", __val);
4099	}
4100
4101	inline string
4102	to_string(double __val)
4103	{
4104	const int __n =
4105	__gnu_cxx::__numeric_traits<double>::__max_exponent10 + `20`;
4106	return __gnu_cxx::__to_xstring<string>(&std::vsnprintf, __n,
4107	"%f", __val);
4108	}
4109
4110	inline string
4111	to_string(long double __val)
4112	{
4113	const int __n =
4114	__gnu_cxx::__numeric_traits<long double>::__max_exponent10 + `20`;
4115	return __gnu_cxx::__to_xstring<string>(&std::vsnprintf, __n,
4116	"%Lf", __val);
4117	}
4118	#endif // _GLIBCXX_USE_C99_STDIO
4119
4120	#if defined(_GLIBCXX_USE_WCHAR_T) && _GLIBCXX_USE_C99_WCHAR
4121	inline int
4122	stoi(const wstring& __str, size_t* __idx = `0`, int __base = `10`)
4123	{ return __gnu_cxx::__stoa<long, int>(&std::wcstol, "stoi", __str.c_str(),
4124	__idx, __base); }
4125
4126	inline long
4127	stol(const wstring& __str, size_t* __idx = `0`, int __base = `10`)
4128	{ return __gnu_cxx::__stoa(&std::wcstol, "stol", __str.c_str(),
4129	__idx, __base); }
4130
4131	inline unsigned long
4132	stoul(const wstring& __str, size_t* __idx = `0`, int __base = `10`)
4133	{ return __gnu_cxx::__stoa(&std::wcstoul, "stoul", __str.c_str(),
4134	__idx, __base); }
4135
4136	inline long long
4137	stoll(const wstring& __str, size_t* __idx = `0`, int __base = `10`)
4138	{ return __gnu_cxx::__stoa(&std::wcstoll, "stoll", __str.c_str(),
4139	__idx, __base); }
4140
4141	inline unsigned long long
4142	stoull(const wstring& __str, size_t* __idx = `0`, int __base = `10`)
4143	{ return __gnu_cxx::__stoa(&std::wcstoull, "stoull", __str.c_str(),
4144	__idx, __base); }
4145
4146	// NB: wcstof vs wcstod.
4147	inline float
4148	stof(const wstring& __str, size_t* __idx = `0`)
4149	{ return __gnu_cxx::__stoa(&std::wcstof, "stof", __str.c_str(), __idx); }
4150
4151	inline double
4152	stod(const wstring& __str, size_t* __idx = `0`)
4153	{ return __gnu_cxx::__stoa(&std::wcstod, "stod", __str.c_str(), __idx); }
4154
4155	inline long double
4156	stold(const wstring& __str, size_t* __idx = `0`)
4157	{ return __gnu_cxx::__stoa(&std::wcstold, "stold", __str.c_str(), __idx); }
4158
4159	#ifndef _GLIBCXX_HAVE_BROKEN_VSWPRINTF
4160	// DR 1261.
4161	inline wstring
4162	to_wstring(int __val)
4163	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, `4` * sizeof(int),
4164	L"%d", __val); }
4165
4166	inline wstring
4167	to_wstring(unsigned __val)
4168	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
4169	`4` * sizeof(unsigned),
4170	L"%u", __val); }
4171
4172	inline wstring
4173	to_wstring(long __val)
4174	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, `4` * sizeof(long),
4175	L"%ld", __val); }
4176
4177	inline wstring
4178	to_wstring(unsigned long __val)
4179	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
4180	`4` * sizeof(unsigned long),
4181	L"%lu", __val); }
4182
4183	inline wstring
4184	to_wstring(long long __val)
4185	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
4186	`4` * sizeof(long long),
4187	L"%lld", __val); }
4188
4189	inline wstring
4190	to_wstring(unsigned long long __val)
4191	{ return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
4192	`4` * sizeof(unsigned long long),
4193	L"%llu", __val); }
4194
4195	inline wstring
4196	to_wstring(float __val)
4197	{
4198	const int __n =
4199	__gnu_cxx::__numeric_traits<float>::__max_exponent10 + `20`;
4200	return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, __n,
4201	L"%f", __val);
4202	}
4203
4204	inline wstring
4205	to_wstring(double __val)
4206	{
4207	const int __n =
4208	__gnu_cxx::__numeric_traits<double>::__max_exponent10 + `20`;
4209	return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, __n,
4210	L"%f", __val);
4211	}
4212
4213	inline wstring
4214	to_wstring(long double __val)
4215	{
4216	const int __n =
4217	__gnu_cxx::__numeric_traits<long double>::__max_exponent10 + `20`;
4218	return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, __n,
4219	L"%Lf", __val);
4220	}
4221	#endif // _GLIBCXX_HAVE_BROKEN_VSWPRINTF
4222	#endif // _GLIBCXX_USE_WCHAR_T && _GLIBCXX_USE_C99_WCHAR
4223
4224	_GLIBCXX_END_NAMESPACE_CXX11
4225	_GLIBCXX_END_NAMESPACE_VERSION
4226	} // namespace
4227
4228	#endif /* C++11 */
4229
4230	#if __cplusplus >= 201103L
4231
4232	#include <bits/functional_hash.h>
4233
4234	namespace std _GLIBCXX_VISIBILITY(default)
4235	{
4236	_GLIBCXX_BEGIN_NAMESPACE_VERSION
4237
4238	// DR 1182.
4239
4240	#ifndef _GLIBCXX_COMPATIBILITY_CXX0X
4241	/// std::hash specialization for string.
4242	template<>
4243	struct hash<string>
4244	: public __hash_base<size_t, string>
4245	{
4246	size_t
4247	operator()(const string& __s) const noexcept
4248	{ return std::_Hash_impl::hash(__s.data(), __s.length()); }
4249	};
4250
4251	template<>
4252	struct __is_fast_hash<hash<string>> : std::false_type
4253	{ };
4254
4255	/// std::hash specialization for wstring.
4256	template<>
4257	struct hash<wstring>
4258	: public __hash_base<size_t, wstring>
4259	{
4260	size_t
4261	operator()(const wstring& __s) const noexcept
4262	{ return std::_Hash_impl::hash(__s.data(),
4263	__s.length() * sizeof(wchar_t)); }
4264	};
4265
4266	template<>
4267	struct __is_fast_hash<hash<wstring>> : std::false_type
4268	{ };
4269	#endif /* _GLIBCXX_COMPATIBILITY_CXX0X */
4270
4271	#ifdef _GLIBCXX_USE_CHAR8_T
4272	/// std::hash specialization for u8string.
4273	template<>
4274	struct hash<u8string>
4275	: public __hash_base<size_t, u8string>
4276	{
4277	size_t
4278	operator()(const u8string& __s) const noexcept
4279	{ return std::_Hash_impl::hash(__s.data(),
4280	__s.length() * sizeof(char8_t)); }
4281	};
4282
4283	template<>
4284	struct __is_fast_hash<hash<u8string>> : std::false_type
4285	{ };
4286	#endif
4287
4288	/// std::hash specialization for u16string.
4289	template<>
4290	struct hash<u16string>
4291	: public __hash_base<size_t, u16string>
4292	{
4293	size_t
4294	operator()(const u16string& __s) const noexcept
4295	{ return std::_Hash_impl::hash(__s.data(),
4296	__s.length() * sizeof(char16_t)); }
4297	};
4298
4299	template<>
4300	struct __is_fast_hash<hash<u16string>> : std::false_type
4301	{ };
4302
4303	/// std::hash specialization for u32string.
4304	template<>
4305	struct hash<u32string>
4306	: public __hash_base<size_t, u32string>
4307	{
4308	size_t
4309	operator()(const u32string& __s) const noexcept
4310	{ return std::_Hash_impl::hash(__s.data(),
4311	__s.length() * sizeof(char32_t)); }
4312	};
4313
4314	template<>
4315	struct __is_fast_hash<hash<u32string>> : std::false_type
4316	{ };
4317
4318	#if __cplusplus >= 201402L
4319
4320	#define __cpp_lib_string_udls 201304L
4321
4322	inline namespace literals
4323	{
4324	inline namespace string_literals
4325	{
4326	#pragma GCC diagnostic push
4327	#pragma GCC diagnostic ignored "-Wliteral-suffix"
4328
4329	#if __cpp_lib_constexpr_string >= 201907L
4330	# define _GLIBCXX_STRING_CONSTEXPR constexpr
4331	#else
4332	# define _GLIBCXX_STRING_CONSTEXPR
4333	#endif
4334
4335	_GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_STRING_CONSTEXPR
4336	inline basic_string<char>
4337	operator""s(const char* __str, size_t __len)
4338	{ return basic_string<char>{__str, __len}; }
4339
4340	_GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_STRING_CONSTEXPR
4341	inline basic_string<wchar_t>
4342	operator""s(const wchar_t* __str, size_t __len)
4343	{ return basic_string<wchar_t>{__str, __len}; }
4344
4345	#ifdef _GLIBCXX_USE_CHAR8_T
4346	_GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_STRING_CONSTEXPR
4347	inline basic_string<char8_t>
4348	operator""s(const char8_t* __str, size_t __len)
4349	{ return basic_string<char8_t>{__str, __len}; }
4350	#endif
4351
4352	_GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_STRING_CONSTEXPR
4353	inline basic_string<char16_t>
4354	operator""s(const char16_t* __str, size_t __len)
4355	{ return basic_string<char16_t>{__str, __len}; }
4356
4357	_GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_STRING_CONSTEXPR
4358	inline basic_string<char32_t>
4359	operator""s(const char32_t* __str, size_t __len)
4360	{ return basic_string<char32_t>{__str, __len}; }
4361
4362	#undef _GLIBCXX_STRING_CONSTEXPR
4363	#pragma GCC diagnostic pop
4364	} // inline namespace string_literals
4365	} // inline namespace literals
4366
4367	#if __cplusplus >= 201703L
4368	namespace __detail::__variant
4369	{
4370	template<typename> struct _Never_valueless_alt; // see <variant>
4371
4372	// Provide the strong exception-safety guarantee when emplacing a
4373	// basic_string into a variant, but only if moving the string cannot throw.
4374	template<typename _Tp, typename _Traits, typename _Alloc>
4375	struct _Never_valueless_alt<std::basic_string<_Tp, _Traits, _Alloc>>
4376	: __and_<
4377	is_nothrow_move_constructible<std::basic_string<_Tp, _Traits, _Alloc>>,
4378	is_nothrow_move_assignable<std::basic_string<_Tp, _Traits, _Alloc>>
4379	>::type
4380	{ };
4381	} // namespace __detail::__variant
4382	#endif // C++17
4383	#endif // C++14
4384
4385	_GLIBCXX_END_NAMESPACE_VERSION
4386	} // namespace std
4387
4388	#endif // C++11
4389
4390	#endif /* _BASIC_STRING_H */
4391

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