include/string

// -*- C++ -*-
//===--------------------------- string -----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_STRING
#define _LIBCPP_STRING

/*
 string synopsis

namespace std
{

template <class stateT>
class fpos
{
private:
 stateT st;
public:
 fpos(streamoff = streamoff());

 operator streamoff() const;

 stateT state() const;
 void state(stateT);

 fpos& operator+=(streamoff);
 fpos operator+ (streamoff) const;
 fpos& operator-=(streamoff);
 fpos operator- (streamoff) const;
};

template <class stateT> streamoff operator-(const fpos<stateT>& x, const fpos<stateT>& y);

template <class stateT> bool operator==(const fpos<stateT>& x, const fpos<stateT>& y);
template <class stateT> bool operator!=(const fpos<stateT>& x, const fpos<stateT>& y);

template <class charT>
struct char_traits
{
 typedef charT char_type;
 typedef ... int_type;
 typedef streamoff off_type;
 typedef streampos pos_type;
 typedef mbstate_t state_type;

 static void assign(char_type& c1, const char_type& c2) noexcept;
 static constexpr bool eq(char_type c1, char_type c2) noexcept;
 static constexpr bool lt(char_type c1, char_type c2) noexcept;

 static int compare(const char_type* s1, const char_type* s2, size_t n);
 static size_t length(const char_type* s);
 static const char_type* find(const char_type* s, size_t n, const char_type& a);
 static char_type* move(char_type* s1, const char_type* s2, size_t n);
 static char_type* copy(char_type* s1, const char_type* s2, size_t n);
 static char_type* assign(char_type* s, size_t n, char_type a);

 static constexpr int_type not_eof(int_type c) noexcept;
 static constexpr char_type to_char_type(int_type c) noexcept;
 static constexpr int_type to_int_type(char_type c) noexcept;
 static constexpr bool eq_int_type(int_type c1, int_type c2) noexcept;
 static constexpr int_type eof() noexcept;
};

template <> struct char_traits<char>;
template <> struct char_traits<wchar_t>;

template<class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
class basic_string
{
public:
// types:
 typedef traits traits_type;
 typedef typename traits_type::char_type value_type;
 typedef Allocator allocator_type;
 typedef typename allocator_type::size_type size_type;
 typedef typename allocator_type::difference_type difference_type;
 typedef typename allocator_type::reference reference;
 typedef typename allocator_type::const_reference const_reference;
 typedef typename allocator_type::pointer pointer;
 typedef typename allocator_type::const_pointer const_pointer;
 typedef implementation-defined iterator;
 typedef implementation-defined const_iterator;
 typedef std::reverse_iterator<iterator> reverse_iterator;
 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

 static const size_type npos = -1;

 basic_string()
 noexcept(is_nothrow_default_constructible<allocator_type>::value);
 explicit basic_string(const allocator_type& a);
 basic_string(const basic_string& str);
 basic_string(basic_string&& str)
 noexcept(is_nothrow_move_constructible<allocator_type>::value);
 basic_string(const basic_string& str, size_type pos, // LWG#2583
 const allocator_type& a = allocator_type());
 basic_string(const basic_string& str, size_type pos, size_type n, // LWG#2583
 const Allocator& a = Allocator()); 
 basic_string(const value_type* s, const allocator_type& a = allocator_type());
 basic_string(const value_type* s, size_type n, const allocator_type& a = allocator_type());
 basic_string(size_type n, value_type c, const allocator_type& a = allocator_type());
 template<class InputIterator>
 basic_string(InputIterator begin, InputIterator end,
 const allocator_type& a = allocator_type());
 basic_string(initializer_list<value_type>, const Allocator& = Allocator());
 basic_string(const basic_string&, const Allocator&);
 basic_string(basic_string&&, const Allocator&);

 ~basic_string();

 basic_string& operator=(const basic_string& str);
 basic_string& operator=(basic_string&& str)
 noexcept(
 allocator_type::propagate_on_container_move_assignment::value ||
 allocator_type::is_always_equal::value ); // C++17
 basic_string& operator=(const value_type* s);
 basic_string& operator=(value_type c);
 basic_string& operator=(initializer_list<value_type>);

 iterator begin() noexcept;
 const_iterator begin() const noexcept;
 iterator end() noexcept;
 const_iterator end() const noexcept;

 reverse_iterator rbegin() noexcept;
 const_reverse_iterator rbegin() const noexcept;
 reverse_iterator rend() noexcept;
 const_reverse_iterator rend() const noexcept;

 const_iterator cbegin() const noexcept;
 const_iterator cend() const noexcept;
 const_reverse_iterator crbegin() const noexcept;
 const_reverse_iterator crend() const noexcept;

 size_type size() const noexcept;
 size_type length() const noexcept;
 size_type max_size() const noexcept;
 size_type capacity() const noexcept;

 void resize(size_type n, value_type c);
 void resize(size_type n);

 void reserve(size_type res_arg = 0);
 void shrink_to_fit();
 void clear() noexcept;
 bool empty() const noexcept;

 const_reference operator[](size_type pos) const;
 reference operator[](size_type pos);

 const_reference at(size_type n) const;
 reference at(size_type n);

 basic_string& operator+=(const basic_string& str);
 basic_string& operator+=(const value_type* s);
 basic_string& operator+=(value_type c);
 basic_string& operator+=(initializer_list<value_type>);

 basic_string& append(const basic_string& str);
 basic_string& append(const basic_string& str, size_type pos, size_type n=npos); //C++14
 basic_string& append(const value_type* s, size_type n);
 basic_string& append(const value_type* s);
 basic_string& append(size_type n, value_type c);
 template<class InputIterator>
 basic_string& append(InputIterator first, InputIterator last);
 basic_string& append(initializer_list<value_type>);

 void push_back(value_type c);
 void pop_back();
 reference front();
 const_reference front() const;
 reference back();
 const_reference back() const;

 basic_string& assign(const basic_string& str);
 basic_string& assign(basic_string&& str);
 basic_string& assign(const basic_string& str, size_type pos, size_type n=npos); // C++14
 basic_string& assign(const value_type* s, size_type n);
 basic_string& assign(const value_type* s);
 basic_string& assign(size_type n, value_type c);
 template<class InputIterator>
 basic_string& assign(InputIterator first, InputIterator last);
 basic_string& assign(initializer_list<value_type>);

 basic_string& insert(size_type pos1, const basic_string& str);
 basic_string& insert(size_type pos1, const basic_string& str,
 size_type pos2, size_type n);
 basic_string& insert(size_type pos, const value_type* s, size_type n=npos); //C++14
 basic_string& insert(size_type pos, const value_type* s);
 basic_string& insert(size_type pos, size_type n, value_type c);
 iterator insert(const_iterator p, value_type c);
 iterator insert(const_iterator p, size_type n, value_type c);
 template<class InputIterator>
 iterator insert(const_iterator p, InputIterator first, InputIterator last);
 iterator insert(const_iterator p, initializer_list<value_type>);

 basic_string& erase(size_type pos = 0, size_type n = npos);
 iterator erase(const_iterator position);
 iterator erase(const_iterator first, const_iterator last);

 basic_string& replace(size_type pos1, size_type n1, const basic_string& str);
 basic_string& replace(size_type pos1, size_type n1, const basic_string& str,
 size_type pos2, size_type n2=npos); // C++14
 basic_string& replace(size_type pos, size_type n1, const value_type* s, size_type n2);
 basic_string& replace(size_type pos, size_type n1, const value_type* s);
 basic_string& replace(size_type pos, size_type n1, size_type n2, value_type c);
 basic_string& replace(const_iterator i1, const_iterator i2, const basic_string& str);
 basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s, size_type n);
 basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s);
 basic_string& replace(const_iterator i1, const_iterator i2, size_type n, value_type c);
 template<class InputIterator>
 basic_string& replace(const_iterator i1, const_iterator i2, InputIterator j1, InputIterator j2);
 basic_string& replace(const_iterator i1, const_iterator i2, initializer_list<value_type>);

 size_type copy(value_type* s, size_type n, size_type pos = 0) const;
 basic_string substr(size_type pos = 0, size_type n = npos) const;

 void swap(basic_string& str)
 noexcept(allocator_traits<allocator_type>::propagate_on_container_swap::value ||
 allocator_traits<allocator_type>::is_always_equal::value); // C++17

 const value_type* c_str() const noexcept;
 const value_type* data() const noexcept;
 value_type* data() noexcept; // C++17

 allocator_type get_allocator() const noexcept;

 size_type find(const basic_string& str, size_type pos = 0) const noexcept;
 size_type find(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type find(const value_type* s, size_type pos = 0) const noexcept;
 size_type find(value_type c, size_type pos = 0) const noexcept;

 size_type rfind(const basic_string& str, size_type pos = npos) const noexcept;
 size_type rfind(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type rfind(const value_type* s, size_type pos = npos) const noexcept;
 size_type rfind(value_type c, size_type pos = npos) const noexcept;

 size_type find_first_of(const basic_string& str, size_type pos = 0) const noexcept;
 size_type find_first_of(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type find_first_of(const value_type* s, size_type pos = 0) const noexcept;
 size_type find_first_of(value_type c, size_type pos = 0) const noexcept;

 size_type find_last_of(const basic_string& str, size_type pos = npos) const noexcept;
 size_type find_last_of(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type find_last_of(const value_type* s, size_type pos = npos) const noexcept;
 size_type find_last_of(value_type c, size_type pos = npos) const noexcept;

 size_type find_first_not_of(const basic_string& str, size_type pos = 0) const noexcept;
 size_type find_first_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type find_first_not_of(const value_type* s, size_type pos = 0) const noexcept;
 size_type find_first_not_of(value_type c, size_type pos = 0) const noexcept;

 size_type find_last_not_of(const basic_string& str, size_type pos = npos) const noexcept;
 size_type find_last_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
 size_type find_last_not_of(const value_type* s, size_type pos = npos) const noexcept;
 size_type find_last_not_of(value_type c, size_type pos = npos) const noexcept;

 int compare(const basic_string& str) const noexcept;
 int compare(size_type pos1, size_type n1, const basic_string& str) const;
 int compare(size_type pos1, size_type n1, const basic_string& str,
 size_type pos2, size_type n2=npos) const; // C++14
 int compare(const value_type* s) const noexcept;
 int compare(size_type pos1, size_type n1, const value_type* s) const;
 int compare(size_type pos1, size_type n1, const value_type* s, size_type n2) const;

 bool __invariants() const;
};

template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs);

template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(const charT* lhs , const basic_string<charT,traits,Allocator>&rhs);

template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(charT lhs, const basic_string<charT,traits,Allocator>& rhs);

template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs);

template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(const basic_string<charT, traits, Allocator>& lhs, charT rhs);

template<class charT, class traits, class Allocator>
bool operator==(const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator==(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator==(const basic_string<charT,traits,Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator!=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator!=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator< (const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator< (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator< (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator> (const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator> (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator> (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator<=(const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator<=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator<=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator>=(const basic_string<charT, traits, Allocator>& lhs,
 const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator>=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;

template<class charT, class traits, class Allocator>
bool operator>=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;

template<class charT, class traits, class Allocator>
void swap(basic_string<charT, traits, Allocator>& lhs,
 basic_string<charT, traits, Allocator>& rhs)
 noexcept(noexcept(lhs.swap(rhs)));

template<class charT, class traits, class Allocator>
basic_istream<charT, traits>&
operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);

template<class charT, class traits, class Allocator>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const basic_string<charT, traits, Allocator>& str);

template<class charT, class traits, class Allocator>
basic_istream<charT, traits>&
getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str,
 charT delim);

template<class charT, class traits, class Allocator>
basic_istream<charT, traits>&
getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);

typedef basic_string<char> string;
typedef basic_string<wchar_t> wstring;
typedef basic_string<char16_t> u16string;
typedef basic_string<char32_t> u32string;

int stoi (const string& str, size_t* idx = 0, int base = 10);
long stol (const string& str, size_t* idx = 0, int base = 10);
unsigned long stoul (const string& str, size_t* idx = 0, int base = 10);
long long stoll (const string& str, size_t* idx = 0, int base = 10);
unsigned long long stoull(const string& str, size_t* idx = 0, int base = 10);

float stof (const string& str, size_t* idx = 0);
double stod (const string& str, size_t* idx = 0);
long double stold(const string& str, size_t* idx = 0);

string to_string(int val);
string to_string(unsigned val);
string to_string(long val);
string to_string(unsigned long val);
string to_string(long long val);
string to_string(unsigned long long val);
string to_string(float val);
string to_string(double val);
string to_string(long double val);

int stoi (const wstring& str, size_t* idx = 0, int base = 10);
long stol (const wstring& str, size_t* idx = 0, int base = 10);
unsigned long stoul (const wstring& str, size_t* idx = 0, int base = 10);
long long stoll (const wstring& str, size_t* idx = 0, int base = 10);
unsigned long long stoull(const wstring& str, size_t* idx = 0, int base = 10);

float stof (const wstring& str, size_t* idx = 0);
double stod (const wstring& str, size_t* idx = 0);
long double stold(const wstring& str, size_t* idx = 0);

wstring to_wstring(int val);
wstring to_wstring(unsigned val);
wstring to_wstring(long val);
wstring to_wstring(unsigned long val);
wstring to_wstring(long long val);
wstring to_wstring(unsigned long long val);
wstring to_wstring(float val);
wstring to_wstring(double val);
wstring to_wstring(long double val);

template <> struct hash<string>;
template <> struct hash<u16string>;
template <> struct hash<u32string>;
template <> struct hash<wstring>;

basic_string<char> operator "" s( const char *str, size_t len ); // C++14
basic_string<wchar_t> operator "" s( const wchar_t *str, size_t len ); // C++14
basic_string<char16_t> operator "" s( const char16_t *str, size_t len ); // C++14
basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++14

} // std

*/

#include <__config>
#include <iosfwd>
#include <cstring>
#include <cstdio> // For EOF.
#include <cwchar>
#include <algorithm>
#include <iterator>
#include <utility>
#include <memory>
#include <stdexcept>
#include <type_traits>
#include <initializer_list>
#include <__functional_base>
#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
#include <cstdint>
#endif
#if defined(_LIBCPP_NO_EXCEPTIONS)
#include <cassert>
#endif

#include <__undef_min_max>

#include <__debug>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

// fpos

template <class _StateT>
class _LIBCPP_TYPE_VIS_ONLY fpos
{
private:
 _StateT __st_;
 streamoff __off_;
public:
 _LIBCPP_INLINE_VISIBILITY fpos(streamoff __off = streamoff()) : __st_(), __off_(__off) {}

 _LIBCPP_INLINE_VISIBILITY operator streamoff() const {return __off_;}

 _LIBCPP_INLINE_VISIBILITY _StateT state() const {return __st_;}
 _LIBCPP_INLINE_VISIBILITY void state(_StateT __st) {__st_ = __st;}

 _LIBCPP_INLINE_VISIBILITY fpos& operator+=(streamoff __off) {__off_ += __off; return *this;}
 _LIBCPP_INLINE_VISIBILITY fpos operator+ (streamoff __off) const {fpos __t(*this); __t += __off; return __t;}
 _LIBCPP_INLINE_VISIBILITY fpos& operator-=(streamoff __off) {__off_ -= __off; return *this;}
 _LIBCPP_INLINE_VISIBILITY fpos operator- (streamoff __off) const {fpos __t(*this); __t -= __off; return __t;}
};

template <class _StateT>
inline _LIBCPP_INLINE_VISIBILITY
streamoff operator-(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
 {return streamoff(__x) - streamoff(__y);}

template <class _StateT>
inline _LIBCPP_INLINE_VISIBILITY
bool operator==(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
 {return streamoff(__x) == streamoff(__y);}

template <class _StateT>
inline _LIBCPP_INLINE_VISIBILITY
bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
 {return streamoff(__x) != streamoff(__y);}

// char_traits

template <class _CharT>
struct _LIBCPP_TYPE_VIS_ONLY char_traits
{
 typedef _CharT char_type;
 typedef int int_type;
 typedef streamoff off_type;
 typedef streampos pos_type;
 typedef mbstate_t state_type;

 static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
 {__c1 = __c2;}
 static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 < __c2;}

 static int compare(const char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static size_t length(const char_type* __s);
 _LIBCPP_INLINE_VISIBILITY
 static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
 static char_type* move(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* copy(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* assign(char_type* __s, size_t __n, char_type __a);

 static inline _LIBCPP_CONSTEXPR int_type not_eof(int_type __c) _NOEXCEPT
 {return eq_int_type(__c, eof()) ? ~eof() : __c;}
 static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
 {return char_type(__c);}
 static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
 {return int_type(__c);}
 static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
 {return int_type(EOF);}
};

template <class _CharT>
int
char_traits<_CharT>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
 for (; __n; --__n, ++__s1, ++__s2)
 {
 if (lt(*__s1, *__s2))
 return -1;
 if (lt(*__s2, *__s1))
 return 1;
 }
 return 0;
}

template <class _CharT>
inline
size_t
char_traits<_CharT>::length(const char_type* __s)
{
 size_t __len = 0;
 for (; !eq(*__s, char_type(0)); ++__s)
 ++__len;
 return __len;
}

template <class _CharT>
inline
const _CharT*
char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a)
{
 for (; __n; --__n)
 {
 if (eq(*__s, __a))
 return __s;
 ++__s;
 }
 return 0;
}

template <class _CharT>
_CharT*
char_traits<_CharT>::move(char_type* __s1, const char_type* __s2, size_t __n)
{
 char_type* __r = __s1;
 if (__s1 < __s2)
 {
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 }
 else if (__s2 < __s1)
 {
 __s1 += __n;
 __s2 += __n;
 for (; __n; --__n)
 assign(*--__s1, *--__s2);
 }
 return __r;
}

template <class _CharT>
inline
_CharT*
char_traits<_CharT>::copy(char_type* __s1, const char_type* __s2, size_t __n)
{
 _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
 char_type* __r = __s1;
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 return __r;
}

template <class _CharT>
inline
_CharT*
char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a)
{
 char_type* __r = __s;
 for (; __n; --__n, ++__s)
 assign(*__s, __a);
 return __r;
}

// char_traits<char>

template <>
struct _LIBCPP_TYPE_VIS_ONLY char_traits<char>
{
 typedef char char_type;
 typedef int int_type;
 typedef streamoff off_type;
 typedef streampos pos_type;
 typedef mbstate_t state_type;

 static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
 {__c1 = __c2;}
 static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
 {return (unsigned char)__c1 < (unsigned char)__c2;}

 static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n)
 {return __n == 0 ? 0 : memcmp(__s1, __s2, __n);}
 static inline size_t length(const char_type* __s) {return strlen(__s);}
 static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a)
 {return __n == 0 ? NULL : (const char_type*) memchr(__s, to_int_type(__a), __n);}
 static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n)
 {return __n == 0 ? __s1 : (char_type*) memmove(__s1, __s2, __n);}
 static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n)
 {
 _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
 return __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
 }
 static inline char_type* assign(char_type* __s, size_t __n, char_type __a)
 {return __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);}

 static inline _LIBCPP_CONSTEXPR int_type not_eof(int_type __c) _NOEXCEPT
 {return eq_int_type(__c, eof()) ? ~eof() : __c;}
 static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
 {return char_type(__c);}
 static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
 {return int_type((unsigned char)__c);}
 static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
 {return int_type(EOF);}
};

// char_traits<wchar_t>

template <>
struct _LIBCPP_TYPE_VIS_ONLY char_traits<wchar_t>
{
 typedef wchar_t char_type;
 typedef wint_t int_type;
 typedef streamoff off_type;
 typedef streampos pos_type;
 typedef mbstate_t state_type;

 static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
 {__c1 = __c2;}
 static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 < __c2;}

 static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n)
 {return __n == 0 ? 0 : wmemcmp(__s1, __s2, __n);}
 static inline size_t length(const char_type* __s)
 {return wcslen(__s);}
 static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a)
 {return __n == 0 ? NULL : (const char_type*)wmemchr(__s, __a, __n);}
 static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n)
 {return __n == 0 ? __s1 : (char_type*)wmemmove(__s1, __s2, __n);}
 static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n)
 {
 _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
 return __n == 0 ? __s1 : (char_type*)wmemcpy(__s1, __s2, __n);
 }
 static inline char_type* assign(char_type* __s, size_t __n, char_type __a)
 {return __n == 0 ? __s : (char_type*)wmemset(__s, __a, __n);}

 static inline _LIBCPP_CONSTEXPR int_type not_eof(int_type __c) _NOEXCEPT
 {return eq_int_type(__c, eof()) ? ~eof() : __c;}
 static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
 {return char_type(__c);}
 static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
 {return int_type(__c);}
 static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
 {return int_type(WEOF);}
};

#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS

template <>
struct _LIBCPP_TYPE_VIS_ONLY char_traits<char16_t>
{
 typedef char16_t char_type;
 typedef uint_least16_t int_type;
 typedef streamoff off_type;
 typedef u16streampos pos_type;
 typedef mbstate_t state_type;

 static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
 {__c1 = __c2;}
 static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 < __c2;}

 _LIBCPP_INLINE_VISIBILITY
 static int compare(const char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static size_t length(const char_type* __s);
 _LIBCPP_INLINE_VISIBILITY
 static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* move(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* copy(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* assign(char_type* __s, size_t __n, char_type __a);

 static inline _LIBCPP_CONSTEXPR int_type not_eof(int_type __c) _NOEXCEPT
 {return eq_int_type(__c, eof()) ? ~eof() : __c;}
 static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
 {return char_type(__c);}
 static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
 {return int_type(__c);}
 static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
 {return int_type(0xFFFF);}
};

inline
int
char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
 for (; __n; --__n, ++__s1, ++__s2)
 {
 if (lt(*__s1, *__s2))
 return -1;
 if (lt(*__s2, *__s1))
 return 1;
 }
 return 0;
}

inline
size_t
char_traits<char16_t>::length(const char_type* __s)
{
 size_t __len = 0;
 for (; !eq(*__s, char_type(0)); ++__s)
 ++__len;
 return __len;
}

inline
const char16_t*
char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a)
{
 for (; __n; --__n)
 {
 if (eq(*__s, __a))
 return __s;
 ++__s;
 }
 return 0;
}

inline
char16_t*
char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
{
 char_type* __r = __s1;
 if (__s1 < __s2)
 {
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 }
 else if (__s2 < __s1)
 {
 __s1 += __n;
 __s2 += __n;
 for (; __n; --__n)
 assign(*--__s1, *--__s2);
 }
 return __r;
}

inline
char16_t*
char_traits<char16_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
{
 _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
 char_type* __r = __s1;
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 return __r;
}

inline
char16_t*
char_traits<char16_t>::assign(char_type* __s, size_t __n, char_type __a)
{
 char_type* __r = __s;
 for (; __n; --__n, ++__s)
 assign(*__s, __a);
 return __r;
}

template <>
struct _LIBCPP_TYPE_VIS_ONLY char_traits<char32_t>
{
 typedef char32_t char_type;
 typedef uint_least32_t int_type;
 typedef streamoff off_type;
 typedef u32streampos pos_type;
 typedef mbstate_t state_type;

 static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
 {__c1 = __c2;}
 static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
 {return __c1 < __c2;}

 _LIBCPP_INLINE_VISIBILITY
 static int compare(const char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static size_t length(const char_type* __s);
 _LIBCPP_INLINE_VISIBILITY
 static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* move(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* copy(char_type* __s1, const char_type* __s2, size_t __n);
 _LIBCPP_INLINE_VISIBILITY
 static char_type* assign(char_type* __s, size_t __n, char_type __a);

 static inline _LIBCPP_CONSTEXPR int_type not_eof(int_type __c) _NOEXCEPT
 {return eq_int_type(__c, eof()) ? ~eof() : __c;}
 static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
 {return char_type(__c);}
 static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
 {return int_type(__c);}
 static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
 {return __c1 == __c2;}
 static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
 {return int_type(0xFFFFFFFF);}
};

inline
int
char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
 for (; __n; --__n, ++__s1, ++__s2)
 {
 if (lt(*__s1, *__s2))
 return -1;
 if (lt(*__s2, *__s1))
 return 1;
 }
 return 0;
}

inline
size_t
char_traits<char32_t>::length(const char_type* __s)
{
 size_t __len = 0;
 for (; !eq(*__s, char_type(0)); ++__s)
 ++__len;
 return __len;
}

inline
const char32_t*
char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a)
{
 for (; __n; --__n)
 {
 if (eq(*__s, __a))
 return __s;
 ++__s;
 }
 return 0;
}

inline
char32_t*
char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
{
 char_type* __r = __s1;
 if (__s1 < __s2)
 {
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 }
 else if (__s2 < __s1)
 {
 __s1 += __n;
 __s2 += __n;
 for (; __n; --__n)
 assign(*--__s1, *--__s2);
 }
 return __r;
}

inline
char32_t*
char_traits<char32_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
{
 _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
 char_type* __r = __s1;
 for (; __n; --__n, ++__s1, ++__s2)
 assign(*__s1, *__s2);
 return __r;
}

inline
char32_t*
char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a)
{
 char_type* __r = __s;
 for (; __n; --__n, ++__s)
 assign(*__s, __a);
 return __r;
}

#endif // _LIBCPP_HAS_NO_UNICODE_CHARS

// helper fns for basic_string

// __str_find
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find(const _CharT *__p, _SizeT __sz, 
 _CharT __c, _SizeT __pos) _NOEXCEPT
{
 if (__pos >= __sz)
 return __npos;
 const _CharT* __r = _Traits::find(__p + __pos, __sz - __pos, __c);
 if (__r == 0)
 return __npos;
 return static_cast<_SizeT>(__r - __p);
}

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find(const _CharT *__p, _SizeT __sz, 
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
 if (__pos > __sz || __sz - __pos < __n)
 return __npos;
 if (__n == 0)
 return __pos;
 const _CharT* __r = 
 _VSTD::__search(__p + __pos, __p + __sz,
 __s, __s + __n, _Traits::eq,
 random_access_iterator_tag(), random_access_iterator_tag()).first;
 if (__r == __p + __sz)
 return __npos;
 return static_cast<_SizeT>(__r - __p);
}


// __str_rfind

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_rfind(const _CharT *__p, _SizeT __sz, 
 _CharT __c, _SizeT __pos) _NOEXCEPT
{
 if (__sz < 1)
 return __npos;
 if (__pos < __sz)
 ++__pos;
 else
 __pos = __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __p;)
 {
 if (_Traits::eq(*--__ps, __c))
 return static_cast<_SizeT>(__ps - __p);
 }
 return __npos;
}

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_rfind(const _CharT *__p, _SizeT __sz, 
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
 __pos = _VSTD::min(__pos, __sz);
 if (__n < __sz - __pos)
 __pos += __n;
 else
 __pos = __sz;
 const _CharT* __r = _VSTD::__find_end(
 __p, __p + __pos, __s, __s + __n, _Traits::eq, 
 random_access_iterator_tag(), random_access_iterator_tag());
 if (__n > 0 && __r == __p + __pos)
 return __npos;
 return static_cast<_SizeT>(__r - __p);
}

// __str_find_first_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find_first_of(const _CharT *__p, _SizeT __sz,
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
 if (__pos >= __sz || __n == 0)
 return __npos;
 const _CharT* __r = _VSTD::__find_first_of_ce
 (__p + __pos, __p + __sz, __s, __s + __n, _Traits::eq );
 if (__r == __p + __sz)
 return __npos;
 return static_cast<_SizeT>(__r - __p);
}


// __str_find_last_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY 
__str_find_last_of(const _CharT *__p, _SizeT __sz,
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
 {
 if (__n != 0)
 {
 if (__pos < __sz)
 ++__pos;
 else
 __pos = __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __p;)
 {
 const _CharT* __r = _Traits::find(__s, __n, *--__ps);
 if (__r)
 return static_cast<_SizeT>(__ps - __p);
 }
 }
 return __npos;
}


// __str_find_first_not_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
 if (__pos < __sz)
 {
 const _CharT* __pe = __p + __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
 if (_Traits::find(__s, __n, *__ps) == 0)
 return static_cast<_SizeT>(__ps - __p);
 }
 return __npos;
}


template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
 _CharT __c, _SizeT __pos) _NOEXCEPT
{
 if (__pos < __sz)
 {
 const _CharT* __pe = __p + __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
 if (!_Traits::eq(*__ps, __c))
 return static_cast<_SizeT>(__ps - __p);
 }
 return __npos;
}


// __str_find_last_not_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
 const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
 if (__pos < __sz)
 ++__pos;
 else
 __pos = __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __p;)
 if (_Traits::find(__s, __n, *--__ps) == 0)
 return static_cast<_SizeT>(__ps - __p);
 return __npos;
}


template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
 _CharT __c, _SizeT __pos) _NOEXCEPT
{
 if (__pos < __sz)
 ++__pos;
 else
 __pos = __sz;
 for (const _CharT* __ps = __p + __pos; __ps != __p;)
 if (!_Traits::eq(*--__ps, __c))
 return static_cast<_SizeT>(__ps - __p);
 return __npos;
}

template<class _Ptr>
size_t _LIBCPP_INLINE_VISIBILITY __do_string_hash(_Ptr __p, _Ptr __e)
{
 typedef typename iterator_traits<_Ptr>::value_type value_type;
 return __murmur2_or_cityhash<size_t>()(__p, (__e-__p)*sizeof(value_type));
}

// basic_string

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __x,
 const basic_string<_CharT, _Traits, _Allocator>& __y);

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const _CharT* __x, const basic_string<_CharT,_Traits,_Allocator>& __y);

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(_CharT __x, const basic_string<_CharT,_Traits,_Allocator>& __y);

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, const _CharT* __y);

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, _CharT __y);

template <bool>
class _LIBCPP_TYPE_VIS_ONLY __basic_string_common
{
protected:
 void __throw_length_error() const;
 void __throw_out_of_range() const;
};

template <bool __b>
void
__basic_string_common<__b>::__throw_length_error() const
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 throw length_error("basic_string");
#else
 assert(!"basic_string length_error");
#endif
}

template <bool __b>
void
__basic_string_common<__b>::__throw_out_of_range() const
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 throw out_of_range("basic_string");
#else
 assert(!"basic_string out_of_range");
#endif
}

#ifdef _LIBCPP_MSVC
#pragma warning( push )
#pragma warning( disable: 4231 )
#endif // _LIBCPP_MSVC
_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS __basic_string_common<true>)
#ifdef _LIBCPP_MSVC
#pragma warning( pop )
#endif // _LIBCPP_MSVC

#ifdef _LIBCPP_NO_EXCEPTIONS
template <class _Iter>
struct __libcpp_string_gets_noexcept_iterator_impl : public true_type {};
#elif defined(_LIBCPP_HAS_NO_NOEXCEPT)
template <class _Iter>
struct __libcpp_string_gets_noexcept_iterator_impl : public false_type {};
#else
template <class _Iter, bool = __is_forward_iterator<_Iter>::value>
struct __libcpp_string_gets_noexcept_iterator_impl : public _LIBCPP_BOOL_CONSTANT((
 noexcept(++(declval<_Iter&>())) && 
 is_nothrow_assignable<_Iter&, _Iter>::value && 
 noexcept(declval<_Iter>() == declval<_Iter>()) && 
 noexcept(*declval<_Iter>())
)) {};

template <class _Iter> 
struct __libcpp_string_gets_noexcept_iterator_impl<_Iter, false> : public false_type {};
#endif


template <class _Iter>
struct __libcpp_string_gets_noexcept_iterator
 : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value || __libcpp_string_gets_noexcept_iterator_impl<_Iter>::value) {};

#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

template <class _CharT, size_t = sizeof(_CharT)>
struct __padding
{
 unsigned char __xx[sizeof(_CharT)-1];
};

template <class _CharT>
struct __padding<_CharT, 1>
{
};

#endif // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

template<class _CharT, class _Traits, class _Allocator>
class _LIBCPP_TYPE_VIS_ONLY basic_string
 : private __basic_string_common<true>
{
public:
 typedef basic_string __self;
 typedef _Traits traits_type;
 typedef typename traits_type::char_type value_type;
 typedef _Allocator allocator_type;
 typedef allocator_traits<allocator_type> __alloc_traits;
 typedef typename __alloc_traits::size_type size_type;
 typedef typename __alloc_traits::difference_type difference_type;
 typedef value_type& reference;
 typedef const value_type& const_reference;
 typedef typename __alloc_traits::pointer pointer;
 typedef typename __alloc_traits::const_pointer const_pointer;

 static_assert(is_pod<value_type>::value, "Character type of basic_string must be a POD");
 static_assert((is_same<_CharT, value_type>::value),
 "traits_type::char_type must be the same type as CharT");
 static_assert((is_same<typename allocator_type::value_type, value_type>::value),
 "Allocator::value_type must be same type as value_type");
#if defined(_LIBCPP_RAW_ITERATORS)
 typedef pointer iterator;
 typedef const_pointer const_iterator;
#else // defined(_LIBCPP_RAW_ITERATORS)
 typedef __wrap_iter<pointer> iterator;
 typedef __wrap_iter<const_pointer> const_iterator;
#endif // defined(_LIBCPP_RAW_ITERATORS)
 typedef _VSTD::reverse_iterator<iterator> reverse_iterator;
 typedef _VSTD::reverse_iterator<const_iterator> const_reverse_iterator;

private:

#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

 struct __long
 {
 pointer __data_;
 size_type __size_;
 size_type __cap_;
 };

#if _LIBCPP_BIG_ENDIAN
 enum {__short_mask = 0x01};
 enum {__long_mask = 0x1ul};
#else // _LIBCPP_BIG_ENDIAN
 enum {__short_mask = 0x80};
 enum {__long_mask = ~(size_type(~0) >> 1)};
#endif // _LIBCPP_BIG_ENDIAN

 enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
 (sizeof(__long) - 1)/sizeof(value_type) : 2};

 struct __short
 {
 value_type __data_[__min_cap];
 struct
 : __padding<value_type>
 {
 unsigned char __size_;
 };
 };

#else

 struct __long
 {
 size_type __cap_;
 size_type __size_;
 pointer __data_;
 };

#if _LIBCPP_BIG_ENDIAN
 enum {__short_mask = 0x80};
 enum {__long_mask = ~(size_type(~0) >> 1)};
#else // _LIBCPP_BIG_ENDIAN
 enum {__short_mask = 0x01};
 enum {__long_mask = 0x1ul};
#endif // _LIBCPP_BIG_ENDIAN

 enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
 (sizeof(__long) - 1)/sizeof(value_type) : 2};

 struct __short
 {
 union
 {
 unsigned char __size_;
 value_type __lx;
 };
 value_type __data_[__min_cap];
 };

#endif // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

 union __ulx{__long __lx; __short __lxx;};

 enum {__n_words = sizeof(__ulx) / sizeof(size_type)};

 struct __raw
 {
 size_type __words[__n_words];
 };

 struct __rep
 {
 union
 {
 __long __l;
 __short __s;
 __raw __r;
 };
 };

 __compressed_pair<__rep, allocator_type> __r_;

public:
 static const size_type npos = -1;

 _LIBCPP_INLINE_VISIBILITY basic_string()
 _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value);

 _LIBCPP_INLINE_VISIBILITY explicit basic_string(const allocator_type& __a)
#if _LIBCPP_STD_VER <= 14
 _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value);
#else
 _NOEXCEPT;
#endif

 basic_string(const basic_string& __str);
 basic_string(const basic_string& __str, const allocator_type& __a);

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 basic_string(basic_string&& __str)
#if _LIBCPP_STD_VER <= 14
 _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
#else
 _NOEXCEPT;
#endif

 _LIBCPP_INLINE_VISIBILITY
 basic_string(basic_string&& __str, const allocator_type& __a);
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY basic_string(const value_type* __s);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(const value_type* __s, const allocator_type& __a);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(const value_type* __s, size_type __n);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(const value_type* __s, size_type __n, const allocator_type& __a);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(size_type __n, value_type __c);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(size_type __n, value_type __c, const allocator_type& __a);
 basic_string(const basic_string& __str, size_type __pos, size_type __n,
 const allocator_type& __a = allocator_type());
 basic_string(const basic_string& __str, size_type __pos,
 const allocator_type& __a = allocator_type());
 template<class _InputIterator>
 _LIBCPP_INLINE_VISIBILITY
 basic_string(_InputIterator __first, _InputIterator __last);
 template<class _InputIterator>
 _LIBCPP_INLINE_VISIBILITY
 basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 basic_string(initializer_list<value_type> __il);
 _LIBCPP_INLINE_VISIBILITY
 basic_string(initializer_list<value_type> __il, const allocator_type& __a);
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 ~basic_string();

 basic_string& operator=(const basic_string& __str);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 basic_string& operator=(basic_string&& __str)
 _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
#endif
 _LIBCPP_INLINE_VISIBILITY basic_string& operator=(const value_type* __s) {return assign(__s);}
 basic_string& operator=(value_type __c);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 basic_string& operator=(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_INLINE_VISIBILITY
 iterator begin() _NOEXCEPT
 {return iterator(this, __get_pointer());}
 _LIBCPP_INLINE_VISIBILITY
 const_iterator begin() const _NOEXCEPT
 {return const_iterator(this, __get_pointer());}
 _LIBCPP_INLINE_VISIBILITY
 iterator end() _NOEXCEPT
 {return iterator(this, __get_pointer() + size());}
 _LIBCPP_INLINE_VISIBILITY
 const_iterator end() const _NOEXCEPT
 {return const_iterator(this, __get_pointer() + size());}
#else
 _LIBCPP_INLINE_VISIBILITY
 iterator begin() _NOEXCEPT
 {return iterator(__get_pointer());}
 _LIBCPP_INLINE_VISIBILITY
 const_iterator begin() const _NOEXCEPT
 {return const_iterator(__get_pointer());}
 _LIBCPP_INLINE_VISIBILITY
 iterator end() _NOEXCEPT
 {return iterator(__get_pointer() + size());}
 _LIBCPP_INLINE_VISIBILITY
 const_iterator end() const _NOEXCEPT
 {return const_iterator(__get_pointer() + size());}
#endif // _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_INLINE_VISIBILITY
 reverse_iterator rbegin() _NOEXCEPT
 {return reverse_iterator(end());}
 _LIBCPP_INLINE_VISIBILITY
 const_reverse_iterator rbegin() const _NOEXCEPT
 {return const_reverse_iterator(end());}
 _LIBCPP_INLINE_VISIBILITY
 reverse_iterator rend() _NOEXCEPT
 {return reverse_iterator(begin());}
 _LIBCPP_INLINE_VISIBILITY
 const_reverse_iterator rend() const _NOEXCEPT
 {return const_reverse_iterator(begin());}

 _LIBCPP_INLINE_VISIBILITY
 const_iterator cbegin() const _NOEXCEPT
 {return begin();}
 _LIBCPP_INLINE_VISIBILITY
 const_iterator cend() const _NOEXCEPT
 {return end();}
 _LIBCPP_INLINE_VISIBILITY
 const_reverse_iterator crbegin() const _NOEXCEPT
 {return rbegin();}
 _LIBCPP_INLINE_VISIBILITY
 const_reverse_iterator crend() const _NOEXCEPT
 {return rend();}

 _LIBCPP_INLINE_VISIBILITY size_type size() const _NOEXCEPT
 {return __is_long() ? __get_long_size() : __get_short_size();}
 _LIBCPP_INLINE_VISIBILITY size_type length() const _NOEXCEPT {return size();}
 _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY size_type capacity() const _NOEXCEPT
 {return (__is_long() ? __get_long_cap()
 : static_cast<size_type>(__min_cap)) - 1;}

 void resize(size_type __n, value_type __c);
 _LIBCPP_INLINE_VISIBILITY void resize(size_type __n) {resize(__n, value_type());}

 void reserve(size_type res_arg = 0);
 _LIBCPP_INLINE_VISIBILITY
 void shrink_to_fit() _NOEXCEPT {reserve();}
 _LIBCPP_INLINE_VISIBILITY
 void clear() _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY bool empty() const _NOEXCEPT {return size() == 0;}

 _LIBCPP_INLINE_VISIBILITY const_reference operator[](size_type __pos) const;
 _LIBCPP_INLINE_VISIBILITY reference operator[](size_type __pos);

 const_reference at(size_type __n) const;
 reference at(size_type __n);

 _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const basic_string& __str) {return append(__str);}
 _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const value_type* __s) {return append(__s);}
 _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(value_type __c) {push_back(__c); return *this;}
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(initializer_list<value_type> __il) {return append(__il);}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 _LIBCPP_INLINE_VISIBILITY
 basic_string& append(const basic_string& __str);
 basic_string& append(const basic_string& __str, size_type __pos, size_type __n=npos);
 basic_string& append(const value_type* __s, size_type __n);
 basic_string& append(const value_type* __s);
 basic_string& append(size_type __n, value_type __c);
 template<class _InputIterator>
 typename enable_if
 <
 __is_exactly_input_iterator<_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 basic_string&
 >::type
 append(_InputIterator __first, _InputIterator __last);
 template<class _ForwardIterator>
 typename enable_if
 <
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 basic_string&
 >::type
 append(_ForwardIterator __first, _ForwardIterator __last);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 basic_string& append(initializer_list<value_type> __il) {return append(__il.begin(), __il.size());}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 void push_back(value_type __c);
 _LIBCPP_INLINE_VISIBILITY
 void pop_back();
 _LIBCPP_INLINE_VISIBILITY reference front();
 _LIBCPP_INLINE_VISIBILITY const_reference front() const;
 _LIBCPP_INLINE_VISIBILITY reference back();
 _LIBCPP_INLINE_VISIBILITY const_reference back() const;

 _LIBCPP_INLINE_VISIBILITY
 basic_string& assign(const basic_string& __str);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 basic_string& assign(basic_string&& str)
 _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
 {*this = _VSTD::move(str); return *this;}
#endif
 basic_string& assign(const basic_string& __str, size_type __pos, size_type __n=npos);
 basic_string& assign(const value_type* __s, size_type __n);
 basic_string& assign(const value_type* __s);
 basic_string& assign(size_type __n, value_type __c);
 template<class _InputIterator>
 typename enable_if
 <
 __is_exactly_input_iterator<_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 basic_string&
 >::type
 assign(_InputIterator __first, _InputIterator __last);
 template<class _ForwardIterator>
 typename enable_if
 <
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 basic_string&
 >::type
 assign(_ForwardIterator __first, _ForwardIterator __last);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 basic_string& assign(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 _LIBCPP_INLINE_VISIBILITY
 basic_string& insert(size_type __pos1, const basic_string& __str);
 basic_string& insert(size_type __pos1, const basic_string& __str, size_type __pos2, size_type __n=npos);
 basic_string& insert(size_type __pos, const value_type* __s, size_type __n);
 basic_string& insert(size_type __pos, const value_type* __s);
 basic_string& insert(size_type __pos, size_type __n, value_type __c);
 iterator insert(const_iterator __pos, value_type __c);
 _LIBCPP_INLINE_VISIBILITY
 iterator insert(const_iterator __pos, size_type __n, value_type __c);
 template<class _InputIterator>
 typename enable_if
 <
 __is_exactly_input_iterator<_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 iterator
 >::type
 insert(const_iterator __pos, _InputIterator __first, _InputIterator __last);
 template<class _ForwardIterator>
 typename enable_if
 <
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 iterator
 >::type
 insert(const_iterator __pos, _ForwardIterator __first, _ForwardIterator __last);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 iterator insert(const_iterator __pos, initializer_list<value_type> __il)
 {return insert(__pos, __il.begin(), __il.end());}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 basic_string& erase(size_type __pos = 0, size_type __n = npos);
 _LIBCPP_INLINE_VISIBILITY
 iterator erase(const_iterator __pos);
 _LIBCPP_INLINE_VISIBILITY
 iterator erase(const_iterator __first, const_iterator __last);

 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str);
 basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos);
 basic_string& replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2);
 basic_string& replace(size_type __pos, size_type __n1, const value_type* __s);
 basic_string& replace(size_type __pos, size_type __n1, size_type __n2, value_type __c);
 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(const_iterator __i1, const_iterator __i2, const basic_string& __str);
 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s, size_type __n);
 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s);
 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(const_iterator __i1, const_iterator __i2, size_type __n, value_type __c);
 template<class _InputIterator>
 typename enable_if
 <
 __is_input_iterator<_InputIterator>::value,
 basic_string&
 >::type
 replace(const_iterator __i1, const_iterator __i2, _InputIterator __j1, _InputIterator __j2);
#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 _LIBCPP_INLINE_VISIBILITY
 basic_string& replace(const_iterator __i1, const_iterator __i2, initializer_list<value_type> __il)
 {return replace(__i1, __i2, __il.begin(), __il.end());}
#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

 size_type copy(value_type* __s, size_type __n, size_type __pos = 0) const;
 _LIBCPP_INLINE_VISIBILITY
 basic_string substr(size_type __pos = 0, size_type __n = npos) const;

 _LIBCPP_INLINE_VISIBILITY
 void swap(basic_string& __str)
#if _LIBCPP_STD_VER >= 14
 _NOEXCEPT;
#else
 _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
 __is_nothrow_swappable<allocator_type>::value);
#endif

 _LIBCPP_INLINE_VISIBILITY
 const value_type* c_str() const _NOEXCEPT {return data();}
 _LIBCPP_INLINE_VISIBILITY
 const value_type* data() const _NOEXCEPT {return _VSTD::__to_raw_pointer(__get_pointer());}
#if _LIBCPP_STD_VER > 14
 _LIBCPP_INLINE_VISIBILITY
 value_type* data() _NOEXCEPT {return _VSTD::__to_raw_pointer(__get_pointer());}
#endif

 _LIBCPP_INLINE_VISIBILITY
 allocator_type get_allocator() const _NOEXCEPT {return __alloc();}

 _LIBCPP_INLINE_VISIBILITY
 size_type find(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
 size_type find(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
 size_type find(value_type __c, size_type __pos = 0) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 size_type rfind(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
 size_type rfind(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type rfind(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
 size_type rfind(value_type __c, size_type __pos = npos) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
 size_type find_first_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_of(value_type __c, size_type __pos = 0) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
 size_type find_last_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_of(value_type __c, size_type __pos = npos) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_not_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
 size_type find_first_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_not_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_first_not_of(value_type __c, size_type __pos = 0) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_not_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
 size_type find_last_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_not_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 size_type find_last_not_of(value_type __c, size_type __pos = npos) const _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 int compare(const basic_string& __str) const _NOEXCEPT;
 _LIBCPP_INLINE_VISIBILITY
 int compare(size_type __pos1, size_type __n1, const basic_string& __str) const;
 int compare(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos) const;
 int compare(const value_type* __s) const _NOEXCEPT;
 int compare(size_type __pos1, size_type __n1, const value_type* __s) const;
 int compare(size_type __pos1, size_type __n1, const value_type* __s, size_type __n2) const;

 _LIBCPP_INLINE_VISIBILITY bool __invariants() const;

 _LIBCPP_INLINE_VISIBILITY
 bool __is_long() const _NOEXCEPT
 {return bool(__r_.first().__s.__size_ & __short_mask);}

#if _LIBCPP_DEBUG_LEVEL >= 2

 bool __dereferenceable(const const_iterator* __i) const;
 bool __decrementable(const const_iterator* __i) const;
 bool __addable(const const_iterator* __i, ptrdiff_t __n) const;
 bool __subscriptable(const const_iterator* __i, ptrdiff_t __n) const;

#endif // _LIBCPP_DEBUG_LEVEL >= 2

private:
 _LIBCPP_INLINE_VISIBILITY
 allocator_type& __alloc() _NOEXCEPT
 {return __r_.second();}
 _LIBCPP_INLINE_VISIBILITY
 const allocator_type& __alloc() const _NOEXCEPT
 {return __r_.second();}

#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

 _LIBCPP_INLINE_VISIBILITY
 void __set_short_size(size_type __s) _NOEXCEPT
# if _LIBCPP_BIG_ENDIAN
 {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
# else
 {__r_.first().__s.__size_ = (unsigned char)(__s);}
# endif

 _LIBCPP_INLINE_VISIBILITY
 size_type __get_short_size() const _NOEXCEPT
# if _LIBCPP_BIG_ENDIAN
 {return __r_.first().__s.__size_ >> 1;}
# else
 {return __r_.first().__s.__size_;}
# endif

#else // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

 _LIBCPP_INLINE_VISIBILITY
 void __set_short_size(size_type __s) _NOEXCEPT
# if _LIBCPP_BIG_ENDIAN
 {__r_.first().__s.__size_ = (unsigned char)(__s);}
# else
 {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
# endif

 _LIBCPP_INLINE_VISIBILITY
 size_type __get_short_size() const _NOEXCEPT
# if _LIBCPP_BIG_ENDIAN
 {return __r_.first().__s.__size_;}
# else
 {return __r_.first().__s.__size_ >> 1;}
# endif

#endif // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT

 _LIBCPP_INLINE_VISIBILITY
 void __set_long_size(size_type __s) _NOEXCEPT
 {__r_.first().__l.__size_ = __s;}
 _LIBCPP_INLINE_VISIBILITY
 size_type __get_long_size() const _NOEXCEPT
 {return __r_.first().__l.__size_;}
 _LIBCPP_INLINE_VISIBILITY
 void __set_size(size_type __s) _NOEXCEPT
 {if (__is_long()) __set_long_size(__s); else __set_short_size(__s);}

 _LIBCPP_INLINE_VISIBILITY
 void __set_long_cap(size_type __s) _NOEXCEPT
 {__r_.first().__l.__cap_ = __long_mask | __s;}
 _LIBCPP_INLINE_VISIBILITY
 size_type __get_long_cap() const _NOEXCEPT
 {return __r_.first().__l.__cap_ & size_type(~__long_mask);}

 _LIBCPP_INLINE_VISIBILITY
 void __set_long_pointer(pointer __p) _NOEXCEPT
 {__r_.first().__l.__data_ = __p;}
 _LIBCPP_INLINE_VISIBILITY
 pointer __get_long_pointer() _NOEXCEPT
 {return __r_.first().__l.__data_;}
 _LIBCPP_INLINE_VISIBILITY
 const_pointer __get_long_pointer() const _NOEXCEPT
 {return __r_.first().__l.__data_;}
 _LIBCPP_INLINE_VISIBILITY
 pointer __get_short_pointer() _NOEXCEPT
 {return pointer_traits<pointer>::pointer_to(__r_.first().__s.__data_[0]);}
 _LIBCPP_INLINE_VISIBILITY
 const_pointer __get_short_pointer() const _NOEXCEPT
 {return pointer_traits<const_pointer>::pointer_to(__r_.first().__s.__data_[0]);}
 _LIBCPP_INLINE_VISIBILITY
 pointer __get_pointer() _NOEXCEPT
 {return __is_long() ? __get_long_pointer() : __get_short_pointer();}
 _LIBCPP_INLINE_VISIBILITY
 const_pointer __get_pointer() const _NOEXCEPT
 {return __is_long() ? __get_long_pointer() : __get_short_pointer();}

 _LIBCPP_INLINE_VISIBILITY
 void __zero() _NOEXCEPT
 {
 size_type (&__a)[__n_words] = __r_.first().__r.__words;
 for (unsigned __i = 0; __i < __n_words; ++__i)
 __a[__i] = 0;
 }

 template <size_type __a> static
 _LIBCPP_INLINE_VISIBILITY
 size_type __align_it(size_type __s) _NOEXCEPT
 {return (__s + (__a-1)) & ~(__a-1);}
 enum {__alignment = 16};
 static _LIBCPP_INLINE_VISIBILITY
 size_type __recommend(size_type __s) _NOEXCEPT
 {return (__s < __min_cap ? static_cast<size_type>(__min_cap) :
 __align_it<sizeof(value_type) < __alignment ?
 __alignment/sizeof(value_type) : 1 > (__s+1)) - 1;}

 void __init(const value_type* __s, size_type __sz, size_type __reserve);
 void __init(const value_type* __s, size_type __sz);
 void __init(size_type __n, value_type __c);

 template <class _InputIterator>
 typename enable_if
 <
 __is_exactly_input_iterator<_InputIterator>::value,
 void
 >::type
 __init(_InputIterator __first, _InputIterator __last);

 template <class _ForwardIterator>
 typename enable_if
 <
 __is_forward_iterator<_ForwardIterator>::value,
 void
 >::type
 __init(_ForwardIterator __first, _ForwardIterator __last);

 void __grow_by(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
 size_type __n_copy, size_type __n_del, size_type __n_add = 0);
 void __grow_by_and_replace(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
 size_type __n_copy, size_type __n_del,
 size_type __n_add, const value_type* __p_new_stuff);

 _LIBCPP_INLINE_VISIBILITY
 void __erase_to_end(size_type __pos);

 _LIBCPP_INLINE_VISIBILITY
 void __copy_assign_alloc(const basic_string& __str)
 {__copy_assign_alloc(__str, integral_constant<bool,
 __alloc_traits::propagate_on_container_copy_assignment::value>());}

 _LIBCPP_INLINE_VISIBILITY
 void __copy_assign_alloc(const basic_string& __str, true_type)
 {
 if (__alloc() != __str.__alloc())
 {
 clear();
 shrink_to_fit();
 }
 __alloc() = __str.__alloc();
 }

 _LIBCPP_INLINE_VISIBILITY
 void __copy_assign_alloc(const basic_string&, false_type) _NOEXCEPT
 {}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 void __move_assign(basic_string& __str, false_type)
 _NOEXCEPT_(__alloc_traits::is_always_equal::value);
 _LIBCPP_INLINE_VISIBILITY
 void __move_assign(basic_string& __str, true_type)
#if _LIBCPP_STD_VER > 14
 _NOEXCEPT;
#else
 _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
#endif
#endif

 _LIBCPP_INLINE_VISIBILITY
 void
 __move_assign_alloc(basic_string& __str)
 _NOEXCEPT_(
 !__alloc_traits::propagate_on_container_move_assignment::value ||
 is_nothrow_move_assignable<allocator_type>::value)
 {__move_assign_alloc(__str, integral_constant<bool,
 __alloc_traits::propagate_on_container_move_assignment::value>());}

 _LIBCPP_INLINE_VISIBILITY
 void __move_assign_alloc(basic_string& __c, true_type)
 _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
 {
 __alloc() = _VSTD::move(__c.__alloc());
 }

 _LIBCPP_INLINE_VISIBILITY
 void __move_assign_alloc(basic_string&, false_type)
 _NOEXCEPT
 {}

 _LIBCPP_INLINE_VISIBILITY void __invalidate_all_iterators();
 _LIBCPP_INLINE_VISIBILITY void __invalidate_iterators_past(size_type);

 friend basic_string operator+<>(const basic_string&, const basic_string&);
 friend basic_string operator+<>(const value_type*, const basic_string&);
 friend basic_string operator+<>(value_type, const basic_string&);
 friend basic_string operator+<>(const basic_string&, const value_type*);
 friend basic_string operator+<>(const basic_string&, value_type);
};

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::__invalidate_all_iterators()
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__invalidate_all(this);
#endif // _LIBCPP_DEBUG_LEVEL >= 2
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::__invalidate_iterators_past(size_type
#if _LIBCPP_DEBUG_LEVEL >= 2
 __pos
#endif
 )
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 __c_node* __c = __get_db()->__find_c_and_lock(this);
 if (__c)
 {
 const_pointer __new_last = __get_pointer() + __pos;
 for (__i_node** __p = __c->end_; __p != __c->beg_; )
 {
 --__p;
 const_iterator* __i = static_cast<const_iterator*>((*__p)->__i_);
 if (__i->base() > __new_last)
 {
 (*__p)->__c_ = nullptr;
 if (--__c->end_ != __p)
 memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
 }
 }
 __get_db()->unlock();
 }
#endif // _LIBCPP_DEBUG_LEVEL >= 2
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string()
 _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
 __zero();
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a)
#if _LIBCPP_STD_VER <= 14
 _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value)
#else
 _NOEXCEPT
#endif
: __r_(__a)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
 __zero();
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_type __sz, size_type __reserve)
{
 if (__reserve > max_size())
 this->__throw_length_error();
 pointer __p;
 if (__reserve < __min_cap)
 {
 __set_short_size(__sz);
 __p = __get_short_pointer();
 }
 else
 {
 size_type __cap = __recommend(__reserve);
 __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
 __set_long_size(__sz);
 }
 traits_type::copy(_VSTD::__to_raw_pointer(__p), __s, __sz);
 traits_type::assign(__p[__sz], value_type());
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_type __sz)
{
 if (__sz > max_size())
 this->__throw_length_error();
 pointer __p;
 if (__sz < __min_cap)
 {
 __set_short_size(__sz);
 __p = __get_short_pointer();
 }
 else
 {
 size_type __cap = __recommend(__sz);
 __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
 __set_long_size(__sz);
 }
 traits_type::copy(_VSTD::__to_raw_pointer(__p), __s, __sz);
 traits_type::assign(__p[__sz], value_type());
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s)
{
 _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
 __init(__s, traits_type::length(__s));
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, const allocator_type& __a)
 : __r_(__a)
{
 _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
 __init(__s, traits_type::length(__s));
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, size_type __n)
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
 __init(__s, __n);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, size_type __n, const allocator_type& __a)
 : __r_(__a)
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
 __init(__s, __n);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
 : __r_(__alloc_traits::select_on_container_copy_construction(__str.__alloc()))
{
 if (!__str.__is_long())
 __r_.first().__r = __str.__r_.first().__r;
 else
 __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, const allocator_type& __a)
 : __r_(__a)
{
 if (!__str.__is_long())
 __r_.first().__r = __str.__r_.first().__r;
 else
 __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str)
#if _LIBCPP_STD_VER <= 14
 _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
#else
 _NOEXCEPT
#endif
 : __r_(_VSTD::move(__str.__r_))
{
 __str.__zero();
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
 if (__is_long())
 __get_db()->swap(this, &__str);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
 : __r_(__a)
{
 if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
 __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
 else
 {
 __r_.first().__r = __str.__r_.first().__r;
 __str.__zero();
 }
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
 if (__is_long())
 __get_db()->swap(this, &__str);
#endif
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
{
 if (__n > max_size())
 this->__throw_length_error();
 pointer __p;
 if (__n < __min_cap)
 {
 __set_short_size(__n);
 __p = __get_short_pointer();
 }
 else
 {
 size_type __cap = __recommend(__n);
 __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
 __set_long_size(__n);
 }
 traits_type::assign(_VSTD::__to_raw_pointer(__p), __n, __c);
 traits_type::assign(__p[__n], value_type());
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_type __c)
{
 __init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_type __c, const allocator_type& __a)
 : __r_(__a)
{
 __init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos, size_type __n,
 const allocator_type& __a)
 : __r_(__a)
{
 size_type __str_sz = __str.size();
 if (__pos > __str_sz)
 this->__throw_out_of_range();
 __init(__str.data() + __pos, _VSTD::min(__n, __str_sz - __pos));
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
 const allocator_type& __a)
 : __r_(__a)
{
 size_type __str_sz = __str.size();
 if (__pos > __str_sz)
 this->__throw_out_of_range();
 __init(__str.data() + __pos, __str_sz - __pos);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
template <class _InputIterator>
typename enable_if
<
 __is_exactly_input_iterator<_InputIterator>::value,
 void
>::type
basic_string<_CharT, _Traits, _Allocator>::__init(_InputIterator __first, _InputIterator __last)
{
 __zero();
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 for (; __first != __last; ++__first)
 push_back(*__first);
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 if (__is_long())
 __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
 throw;
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template <class _CharT, class _Traits, class _Allocator>
template <class _ForwardIterator>
typename enable_if
<
 __is_forward_iterator<_ForwardIterator>::value,
 void
>::type
basic_string<_CharT, _Traits, _Allocator>::__init(_ForwardIterator __first, _ForwardIterator __last)
{
 size_type __sz = static_cast<size_type>(_VSTD::distance(__first, __last));
 if (__sz > max_size())
 this->__throw_length_error();
 pointer __p;
 if (__sz < __min_cap)
 {
 __set_short_size(__sz);
 __p = __get_short_pointer();
 }
 else
 {
 size_type __cap = __recommend(__sz);
 __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
 __set_long_size(__sz);
 }
 for (; __first != __last; ++__first, (void) ++__p)
 traits_type::assign(*__p, *__first);
 traits_type::assign(*__p, value_type());
}

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last)
{
 __init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
 const allocator_type& __a)
 : __r_(__a)
{
 __init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_type> __il)
{
 __init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_type> __il, const allocator_type& __a)
 : __r_(__a)
{
 __init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_c(this);
#endif
}

#endif // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::~basic_string()
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__erase_c(this);
#endif
 if (__is_long())
 __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace
 (size_type __old_cap, size_type __delta_cap, size_type __old_sz,
 size_type __n_copy, size_type __n_del, size_type __n_add, const value_type* __p_new_stuff)
{
 size_type __ms = max_size();
 if (__delta_cap > __ms - __old_cap - 1)
 this->__throw_length_error();
 pointer __old_p = __get_pointer();
 size_type __cap = __old_cap < __ms / 2 - __alignment ?
 __recommend(_VSTD::max(__old_cap + __delta_cap, 2 * __old_cap)) :
 __ms - 1;
 pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __invalidate_all_iterators();
 if (__n_copy != 0)
 traits_type::copy(_VSTD::__to_raw_pointer(__p),
 _VSTD::__to_raw_pointer(__old_p), __n_copy);
 if (__n_add != 0)
 traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy, __p_new_stuff, __n_add);
 size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
 if (__sec_cp_sz != 0)
 traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy + __n_add,
 _VSTD::__to_raw_pointer(__old_p) + __n_copy + __n_del, __sec_cp_sz);
 if (__old_cap+1 != __min_cap)
 __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
 __old_sz = __n_copy + __n_add + __sec_cp_sz;
 __set_long_size(__old_sz);
 traits_type::assign(__p[__old_sz], value_type());
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::__grow_by(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
 size_type __n_copy, size_type __n_del, size_type __n_add)
{
 size_type __ms = max_size();
 if (__delta_cap > __ms - __old_cap)
 this->__throw_length_error();
 pointer __old_p = __get_pointer();
 size_type __cap = __old_cap < __ms / 2 - __alignment ?
 __recommend(_VSTD::max(__old_cap + __delta_cap, 2 * __old_cap)) :
 __ms - 1;
 pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
 __invalidate_all_iterators();
 if (__n_copy != 0)
 traits_type::copy(_VSTD::__to_raw_pointer(__p),
 _VSTD::__to_raw_pointer(__old_p), __n_copy);
 size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
 if (__sec_cp_sz != 0)
 traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy + __n_add,
 _VSTD::__to_raw_pointer(__old_p) + __n_copy + __n_del,
 __sec_cp_sz);
 if (__old_cap+1 != __min_cap)
 __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
 __set_long_pointer(__p);
 __set_long_cap(__cap+1);
}

// assign

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s, size_type __n)
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::assign received nullptr");
 size_type __cap = capacity();
 if (__cap >= __n)
 {
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 traits_type::move(__p, __s, __n);
 traits_type::assign(__p[__n], value_type());
 __set_size(__n);
 __invalidate_iterators_past(__n);
 }
 else
 {
 size_type __sz = size();
 __grow_by_and_replace(__cap, __n - __cap, __sz, 0, __sz, __n, __s);
 }
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::assign(size_type __n, value_type __c)
{
 size_type __cap = capacity();
 if (__cap < __n)
 {
 size_type __sz = size();
 __grow_by(__cap, __n - __cap, __sz, 0, __sz);
 }
 else
 __invalidate_iterators_past(__n);
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 traits_type::assign(__p, __n, __c);
 traits_type::assign(__p[__n], value_type());
 __set_size(__n);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::operator=(value_type __c)
{
 pointer __p;
 if (__is_long())
 {
 __p = __get_long_pointer();
 __set_long_size(1);
 }
 else
 {
 __p = __get_short_pointer();
 __set_short_size(1);
 }
 traits_type::assign(*__p, __c);
 traits_type::assign(*++__p, value_type());
 __invalidate_iterators_past(1);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::operator=(const basic_string& __str)
{
 if (this != &__str)
 {
 __copy_assign_alloc(__str);
 assign(__str);
 }
 return *this;
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, false_type)
 _NOEXCEPT_(__alloc_traits::is_always_equal::value)
{
 if (__alloc() != __str.__alloc())
 assign(__str);
 else
 __move_assign(__str, true_type());
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, true_type)
#if _LIBCPP_STD_VER > 14
 _NOEXCEPT
#else
 _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
#endif
{
 clear();
 shrink_to_fit();
 __r_.first() = __str.__r_.first();
 __move_assign_alloc(__str);
 __str.__zero();
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::operator=(basic_string&& __str)
 _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
{
 __move_assign(__str, integral_constant<bool,
 __alloc_traits::propagate_on_container_move_assignment::value>());
 return *this;
}

#endif

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
typename enable_if
<
 __is_exactly_input_iterator <_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 basic_string<_CharT, _Traits, _Allocator>&
>::type
basic_string<_CharT, _Traits, _Allocator>::assign(_InputIterator __first, _InputIterator __last)
{
 basic_string __temp(__first, __last, __alloc());
 assign(__temp.data(), __temp.size());
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
template<class _ForwardIterator>
typename enable_if
<
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 basic_string<_CharT, _Traits, _Allocator>&
>::type
basic_string<_CharT, _Traits, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
{
 size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
 size_type __cap = capacity();
 if (__cap < __n)
 {
 size_type __sz = size();
 __grow_by(__cap, __n - __cap, __sz, 0, __sz);
 }
 else
 __invalidate_iterators_past(__n);
 pointer __p = __get_pointer();
 for (; __first != __last; ++__first, ++__p)
 traits_type::assign(*__p, *__first);
 traits_type::assign(*__p, value_type());
 __set_size(__n);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::assign(const basic_string& __str)
{
 return assign(__str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::assign(const basic_string& __str, size_type __pos, size_type __n)
{
 size_type __sz = __str.size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 return assign(__str.data() + __pos, _VSTD::min(__n, __sz - __pos));
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s)
{
 _LIBCPP_ASSERT(__s != nullptr, "string::assign received nullptr");
 return assign(__s, traits_type::length(__s));
}

// append

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s, size_type __n)
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::append received nullptr");
 size_type __cap = capacity();
 size_type __sz = size();
 if (__cap - __sz >= __n)
 {
 if (__n)
 {
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 traits_type::copy(__p + __sz, __s, __n);
 __sz += __n;
 __set_size(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 }
 else
 __grow_by_and_replace(__cap, __sz + __n - __cap, __sz, __sz, 0, __n, __s);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::append(size_type __n, value_type __c)
{
 if (__n)
 {
 size_type __cap = capacity();
 size_type __sz = size();
 if (__cap - __sz < __n)
 __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
 pointer __p = __get_pointer();
 traits_type::assign(_VSTD::__to_raw_pointer(__p) + __sz, __n, __c);
 __sz += __n;
 __set_size(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::push_back(value_type __c)
{
 bool __is_short = !__is_long();
 size_type __cap;
 size_type __sz;
 if (__is_short)
 {
 __cap = __min_cap - 1;
 __sz = __get_short_size();
 }
 else
 {
 __cap = __get_long_cap() - 1;
 __sz = __get_long_size();
 }
 if (__sz == __cap)
 {
 __grow_by(__cap, 1, __sz, __sz, 0);
 __is_short = !__is_long();
 }
 pointer __p;
 if (__is_short)
 {
 __p = __get_short_pointer() + __sz;
 __set_short_size(__sz+1);
 }
 else
 {
 __p = __get_long_pointer() + __sz;
 __set_long_size(__sz+1);
 }
 traits_type::assign(*__p, __c);
 traits_type::assign(*++__p, value_type());
}

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
typename enable_if
<
 __is_exactly_input_iterator<_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 basic_string<_CharT, _Traits, _Allocator>&
>::type
basic_string<_CharT, _Traits, _Allocator>::append(_InputIterator __first, _InputIterator __last)
{
basic_string __temp (__first, __last, __alloc());
append(__temp.data(), __temp.size());
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
template<class _ForwardIterator>
typename enable_if
<
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 basic_string<_CharT, _Traits, _Allocator>&
>::type
basic_string<_CharT, _Traits, _Allocator>::append(_ForwardIterator __first, _ForwardIterator __last)
{
 size_type __sz = size();
 size_type __cap = capacity();
 size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
 if (__n)
 {
 if (__cap - __sz < __n)
 __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
 pointer __p = __get_pointer() + __sz;
 for (; __first != __last; ++__p, ++__first)
 traits_type::assign(*__p, *__first);
 traits_type::assign(*__p, value_type());
 __set_size(__sz + __n);
 }
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::append(const basic_string& __str)
{
 return append(__str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::append(const basic_string& __str, size_type __pos, size_type __n)
{
 size_type __sz = __str.size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 return append(__str.data() + __pos, _VSTD::min(__n, __sz - __pos));
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s)
{
 _LIBCPP_ASSERT(__s != nullptr, "string::append received nullptr");
 return append(__s, traits_type::length(__s));
}

// insert

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_type* __s, size_type __n)
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::insert received nullptr");
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 size_type __cap = capacity();
 if (__cap - __sz >= __n)
 {
 if (__n)
 {
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 size_type __n_move = __sz - __pos;
 if (__n_move != 0)
 {
 if (__p + __pos <= __s && __s < __p + __sz)
 __s += __n;
 traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
 }
 traits_type::move(__p + __pos, __s, __n);
 __sz += __n;
 __set_size(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 }
 else
 __grow_by_and_replace(__cap, __sz + __n - __cap, __sz, __pos, 0, __n, __s);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, size_type __n, value_type __c)
{
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 if (__n)
 {
 size_type __cap = capacity();
 value_type* __p;
 if (__cap - __sz >= __n)
 {
 __p = _VSTD::__to_raw_pointer(__get_pointer());
 size_type __n_move = __sz - __pos;
 if (__n_move != 0)
 traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
 }
 else
 {
 __grow_by(__cap, __sz + __n - __cap, __sz, __pos, 0, __n);
 __p = _VSTD::__to_raw_pointer(__get_long_pointer());
 }
 traits_type::assign(__p + __pos, __n, __c);
 __sz += __n;
 __set_size(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
typename enable_if
<
 __is_exactly_input_iterator<_InputIterator>::value
 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
 typename basic_string<_CharT, _Traits, _Allocator>::iterator
>::type
basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _InputIterator __first, _InputIterator __last)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
 "string::insert(iterator, range) called with an iterator not"
 " referring to this string");
#endif
 basic_string __temp(__first, __last, __alloc());
 return insert(__pos, __temp.data(), __temp.data() + __temp.size());
}

template <class _CharT, class _Traits, class _Allocator>
template<class _ForwardIterator>
typename enable_if
<
 __is_forward_iterator<_ForwardIterator>::value
 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
 typename basic_string<_CharT, _Traits, _Allocator>::iterator
>::type
basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _ForwardIterator __first, _ForwardIterator __last)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
 "string::insert(iterator, range) called with an iterator not"
 " referring to this string");
#endif
 size_type __ip = static_cast<size_type>(__pos - begin());
 size_type __sz = size();
 size_type __cap = capacity();
 size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
 if (__n)
 {
 value_type* __p;
 if (__cap - __sz >= __n)
 {
 __p = _VSTD::__to_raw_pointer(__get_pointer());
 size_type __n_move = __sz - __ip;
 if (__n_move != 0)
 traits_type::move(__p + __ip + __n, __p + __ip, __n_move);
 }
 else
 {
 __grow_by(__cap, __sz + __n - __cap, __sz, __ip, 0, __n);
 __p = _VSTD::__to_raw_pointer(__get_long_pointer());
 }
 __sz += __n;
 __set_size(__sz);
 traits_type::assign(__p[__sz], value_type());
 for (__p += __ip; __first != __last; ++__p, ++__first)
 traits_type::assign(*__p, *__first);
 }
 return begin() + __ip;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const basic_string& __str)
{
 return insert(__pos1, __str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const basic_string& __str,
 size_type __pos2, size_type __n)
{
 size_type __str_sz = __str.size();
 if (__pos2 > __str_sz)
 this->__throw_out_of_range();
 return insert(__pos1, __str.data() + __pos2, _VSTD::min(__n, __str_sz - __pos2));
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_type* __s)
{
 _LIBCPP_ASSERT(__s != nullptr, "string::insert received nullptr");
 return insert(__pos, __s, traits_type::length(__s));
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::iterator
basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, value_type __c)
{
 size_type __ip = static_cast<size_type>(__pos - begin());
 size_type __sz = size();
 size_type __cap = capacity();
 value_type* __p;
 if (__cap == __sz)
 {
 __grow_by(__cap, 1, __sz, __ip, 0, 1);
 __p = _VSTD::__to_raw_pointer(__get_long_pointer());
 }
 else
 {
 __p = _VSTD::__to_raw_pointer(__get_pointer());
 size_type __n_move = __sz - __ip;
 if (__n_move != 0)
 traits_type::move(__p + __ip + 1, __p + __ip, __n_move);
 }
 traits_type::assign(__p[__ip], __c);
 traits_type::assign(__p[++__sz], value_type());
 __set_size(__sz);
 return begin() + static_cast<difference_type>(__ip);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::iterator
basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, size_type __n, value_type __c)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
 "string::insert(iterator, n, value) called with an iterator not"
 " referring to this string");
#endif
 difference_type __p = __pos - begin();
 insert(static_cast<size_type>(__p), __n, __c);
 return begin() + __p;
}

// replace

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2)
{
 _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::replace received nullptr");
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 __n1 = _VSTD::min(__n1, __sz - __pos);
 size_type __cap = capacity();
 if (__cap - __sz + __n1 >= __n2)
 {
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 if (__n1 != __n2)
 {
 size_type __n_move = __sz - __pos - __n1;
 if (__n_move != 0)
 {
 if (__n1 > __n2)
 {
 traits_type::move(__p + __pos, __s, __n2);
 traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
 goto __finish;
 }
 if (__p + __pos < __s && __s < __p + __sz)
 {
 if (__p + __pos + __n1 <= __s)
 __s += __n2 - __n1;
 else // __p + __pos < __s < __p + __pos + __n1
 {
 traits_type::move(__p + __pos, __s, __n1);
 __pos += __n1;
 __s += __n2;
 __n2 -= __n1;
 __n1 = 0;
 }
 }
 traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
 }
 }
 traits_type::move(__p + __pos, __s, __n2);
__finish:
 __sz += __n2 - __n1;
 __set_size(__sz);
 __invalidate_iterators_past(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 else
 __grow_by_and_replace(__cap, __sz - __n1 + __n2 - __cap, __sz, __pos, __n1, __n2, __s);
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, size_type __n2, value_type __c)
{
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 __n1 = _VSTD::min(__n1, __sz - __pos);
 size_type __cap = capacity();
 value_type* __p;
 if (__cap - __sz + __n1 >= __n2)
 {
 __p = _VSTD::__to_raw_pointer(__get_pointer());
 if (__n1 != __n2)
 {
 size_type __n_move = __sz - __pos - __n1;
 if (__n_move != 0)
 traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
 }
 }
 else
 {
 __grow_by(__cap, __sz - __n1 + __n2 - __cap, __sz, __pos, __n1, __n2);
 __p = _VSTD::__to_raw_pointer(__get_long_pointer());
 }
 traits_type::assign(__p + __pos, __n2, __c);
 __sz += __n2 - __n1;
 __set_size(__sz);
 __invalidate_iterators_past(__sz);
 traits_type::assign(__p[__sz], value_type());
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator>
typename enable_if
<
 __is_input_iterator<_InputIterator>::value,
 basic_string<_CharT, _Traits, _Allocator>&
>::type
basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2,
 _InputIterator __j1, _InputIterator __j2)
{
 basic_string __temp(__j1, __j2, __alloc());
 return this->replace(__i1, __i2, __temp);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const basic_string& __str)
{
 return replace(__pos1, __n1, __str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const basic_string& __str,
 size_type __pos2, size_type __n2)
{
 size_type __str_sz = __str.size();
 if (__pos2 > __str_sz)
 this->__throw_out_of_range();
 return replace(__pos1, __n1, __str.data() + __pos2, _VSTD::min(__n2, __str_sz - __pos2));
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s)
{
 _LIBCPP_ASSERT(__s != nullptr, "string::replace received nullptr");
 return replace(__pos, __n1, __s, traits_type::length(__s));
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const basic_string& __str)
{
 return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1),
 __str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const value_type* __s, size_type __n)
{
 return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __s, __n);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const value_type* __s)
{
 return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __s);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, size_type __n, value_type __c)
{
 return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __n, __c);
}

// erase

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::erase(size_type __pos, size_type __n)
{
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 if (__n)
 {
 value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
 __n = _VSTD::min(__n, __sz - __pos);
 size_type __n_move = __sz - __pos - __n;
 if (__n_move != 0)
 traits_type::move(__p + __pos, __p + __pos + __n, __n_move);
 __sz -= __n;
 __set_size(__sz);
 __invalidate_iterators_past(__sz);
 traits_type::assign(__p[__sz], value_type());
 }
 return *this;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::iterator
basic_string<_CharT, _Traits, _Allocator>::erase(const_iterator __pos)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
 "string::erase(iterator) called with an iterator not"
 " referring to this string");
#endif
 _LIBCPP_ASSERT(__pos != end(),
 "string::erase(iterator) called with a non-dereferenceable iterator");
 iterator __b = begin();
 size_type __r = static_cast<size_type>(__pos - __b);
 erase(__r, 1);
 return __b + static_cast<difference_type>(__r);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::iterator
basic_string<_CharT, _Traits, _Allocator>::erase(const_iterator __first, const_iterator __last)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__first) == this,
 "string::erase(iterator, iterator) called with an iterator not"
 " referring to this string");
#endif
 _LIBCPP_ASSERT(__first <= __last, "string::erase(first, last) called with invalid range");
 iterator __b = begin();
 size_type __r = static_cast<size_type>(__first - __b);
 erase(__r, static_cast<size_type>(__last - __first));
 return __b + static_cast<difference_type>(__r);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::pop_back()
{
 _LIBCPP_ASSERT(!empty(), "string::pop_back(): string is already empty");
 size_type __sz;
 if (__is_long())
 {
 __sz = __get_long_size() - 1;
 __set_long_size(__sz);
 traits_type::assign(*(__get_long_pointer() + __sz), value_type());
 }
 else
 {
 __sz = __get_short_size() - 1;
 __set_short_size(__sz);
 traits_type::assign(*(__get_short_pointer() + __sz), value_type());
 }
 __invalidate_iterators_past(__sz);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::clear() _NOEXCEPT
{
 __invalidate_all_iterators();
 if (__is_long())
 {
 traits_type::assign(*__get_long_pointer(), value_type());
 __set_long_size(0);
 }
 else
 {
 traits_type::assign(*__get_short_pointer(), value_type());
 __set_short_size(0);
 }
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::__erase_to_end(size_type __pos)
{
 if (__is_long())
 {
 traits_type::assign(*(__get_long_pointer() + __pos), value_type());
 __set_long_size(__pos);
 }
 else
 {
 traits_type::assign(*(__get_short_pointer() + __pos), value_type());
 __set_short_size(__pos);
 }
 __invalidate_iterators_past(__pos);
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::resize(size_type __n, value_type __c)
{
 size_type __sz = size();
 if (__n > __sz)
 append(__n - __sz, __c);
 else
 __erase_to_end(__n);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::max_size() const _NOEXCEPT
{
 size_type __m = __alloc_traits::max_size(__alloc());
#if _LIBCPP_BIG_ENDIAN
 return (__m <= ~__long_mask ? __m : __m/2) - __alignment;
#else
 return __m - __alignment;
#endif
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_string<_CharT, _Traits, _Allocator>::reserve(size_type __res_arg)
{
 if (__res_arg > max_size())
 this->__throw_length_error();
 size_type __cap = capacity();
 size_type __sz = size();
 __res_arg = _VSTD::max(__res_arg, __sz);
 __res_arg = __recommend(__res_arg);
 if (__res_arg != __cap)
 {
 pointer __new_data, __p;
 bool __was_long, __now_long;
 if (__res_arg == __min_cap - 1)
 {
 __was_long = true;
 __now_long = false;
 __new_data = __get_short_pointer();
 __p = __get_long_pointer();
 }
 else
 {
 if (__res_arg > __cap)
 __new_data = __alloc_traits::allocate(__alloc(), __res_arg+1);
 else
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
 #endif // _LIBCPP_NO_EXCEPTIONS
 __new_data = __alloc_traits::allocate(__alloc(), __res_arg+1);
 #ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 return;
 }
 #else // _LIBCPP_NO_EXCEPTIONS
 if (__new_data == nullptr)
 return;
 #endif // _LIBCPP_NO_EXCEPTIONS
 }
 __now_long = true;
 __was_long = __is_long();
 __p = __get_pointer();
 }
 traits_type::copy(_VSTD::__to_raw_pointer(__new_data),
 _VSTD::__to_raw_pointer(__p), size()+1);
 if (__was_long)
 __alloc_traits::deallocate(__alloc(), __p, __cap+1);
 if (__now_long)
 {
 __set_long_cap(__res_arg+1);
 __set_long_size(__sz);
 __set_long_pointer(__new_data);
 }
 else
 __set_short_size(__sz);
 __invalidate_all_iterators();
 }
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::const_reference
basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) const
{
 _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
 return *(data() + __pos);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::reference
basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos)
{
 _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
 return *(__get_pointer() + __pos);
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::const_reference
basic_string<_CharT, _Traits, _Allocator>::at(size_type __n) const
{
 if (__n >= size())
 this->__throw_out_of_range();
 return (*this)[__n];
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::reference
basic_string<_CharT, _Traits, _Allocator>::at(size_type __n)
{
 if (__n >= size())
 this->__throw_out_of_range();
 return (*this)[__n];
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::reference
basic_string<_CharT, _Traits, _Allocator>::front()
{
 _LIBCPP_ASSERT(!empty(), "string::front(): string is empty");
 return *__get_pointer();
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::const_reference
basic_string<_CharT, _Traits, _Allocator>::front() const
{
 _LIBCPP_ASSERT(!empty(), "string::front(): string is empty");
 return *data();
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::reference
basic_string<_CharT, _Traits, _Allocator>::back()
{
 _LIBCPP_ASSERT(!empty(), "string::back(): string is empty");
 return *(__get_pointer() + size() - 1);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::const_reference
basic_string<_CharT, _Traits, _Allocator>::back() const
{
 _LIBCPP_ASSERT(!empty(), "string::back(): string is empty");
 return *(data() + size() - 1);
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::copy(value_type* __s, size_type __n, size_type __pos) const
{
 size_type __sz = size();
 if (__pos > __sz)
 this->__throw_out_of_range();
 size_type __rlen = _VSTD::min(__n, __sz - __pos);
 traits_type::copy(__s, data() + __pos, __rlen);
 return __rlen;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
basic_string<_CharT, _Traits, _Allocator>::substr(size_type __pos, size_type __n) const
{
 return basic_string(*this, __pos, __n, __alloc());
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
basic_string<_CharT, _Traits, _Allocator>::swap(basic_string& __str)
#if _LIBCPP_STD_VER >= 14
 _NOEXCEPT
#else
 _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
 __is_nothrow_swappable<allocator_type>::value)
#endif
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 if (!__is_long())
 __get_db()->__invalidate_all(this);
 if (!__str.__is_long())
 __get_db()->__invalidate_all(&__str);
 __get_db()->swap(this, &__str);
#endif
 _VSTD::swap(__r_.first(), __str.__r_.first());
 __swap_allocator(__alloc(), __str.__alloc());
}

// find

template <class _Traits>
struct _LIBCPP_HIDDEN __traits_eq
{
 typedef typename _Traits::char_type char_type;
 _LIBCPP_INLINE_VISIBILITY
 bool operator()(const char_type& __x, const char_type& __y) _NOEXCEPT
 {return _Traits::eq(__x, __y);}
};

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find(): received nullptr");
 return _VSTD::__str_find<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::find(): received nullptr");
 return _VSTD::__str_find<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find<value_type, size_type, traits_type, npos>
 (data(), size(), __c, __pos);
}

// rfind

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::rfind(): received nullptr");
 return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::rfind(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::rfind(): received nullptr");
 return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::rfind(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
 (data(), size(), __c, __pos);
}

// find_first_of

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_of(): received nullptr");
 return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_of(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::find_first_of(): received nullptr");
 return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_of(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return find(__c, __pos);
}

// find_last_of

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_of(): received nullptr");
 return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_of(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::find_last_of(): received nullptr");
 return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_of(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return rfind(__c, __pos);
}

// find_first_not_of

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_not_of(): received nullptr");
 return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::find_first_not_of(): received nullptr");
 return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __c, __pos);
}

// find_last_not_of

template<class _CharT, class _Traits, class _Allocator>
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __s,
 size_type __pos,
 size_type __n) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_not_of(): received nullptr");
 return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, __n);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const basic_string& __str,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __str.data(), __pos, __str.size());
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __s,
 size_type __pos) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::find_last_not_of(): received nullptr");
 return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __s, __pos, traits_type::length(__s));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(value_type __c,
 size_type __pos) const _NOEXCEPT
{
 return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
 (data(), size(), __c, __pos);
}

// compare

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
int
basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) const _NOEXCEPT
{
 size_t __lhs_sz = size();
 size_t __rhs_sz = __str.size();
 int __result = traits_type::compare(data(), __str.data(),
 _VSTD::min(__lhs_sz, __rhs_sz));
 if (__result != 0)
 return __result;
 if (__lhs_sz < __rhs_sz)
 return -1;
 if (__lhs_sz > __rhs_sz)
 return 1;
 return 0;
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
int
basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
 size_type __n1,
 const basic_string& __str) const
{
 return compare(__pos1, __n1, __str.data(), __str.size());
}

template <class _CharT, class _Traits, class _Allocator>
int
basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
 size_type __n1,
 const basic_string& __str,
 size_type __pos2,
 size_type __n2) const
{
 size_type __sz = __str.size();
 if (__pos2 > __sz)
 this->__throw_out_of_range();
 return compare(__pos1, __n1, __str.data() + __pos2, _VSTD::min(__n2,
 __sz - __pos2));
}

template <class _CharT, class _Traits, class _Allocator>
int
basic_string<_CharT, _Traits, _Allocator>::compare(const value_type* __s) const _NOEXCEPT
{
 _LIBCPP_ASSERT(__s != nullptr, "string::compare(): received nullptr");
 return compare(0, npos, __s, traits_type::length(__s));
}

template <class _CharT, class _Traits, class _Allocator>
int
basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
 size_type __n1,
 const value_type* __s) const
{
 _LIBCPP_ASSERT(__s != nullptr, "string::compare(): received nullptr");
 return compare(__pos1, __n1, __s, traits_type::length(__s));
}

template <class _CharT, class _Traits, class _Allocator>
int
basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
 size_type __n1,
 const value_type* __s,
 size_type __n2) const
{
 _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::compare(): received nullptr");
 size_type __sz = size();
 if (__pos1 > __sz || __n2 == npos)
 this->__throw_out_of_range();
 size_type __rlen = _VSTD::min(__n1, __sz - __pos1);
 int __r = traits_type::compare(data() + __pos1, __s, _VSTD::min(__rlen, __n2));
 if (__r == 0)
 {
 if (__rlen < __n2)
 __r = -1;
 else if (__rlen > __n2)
 __r = 1;
 }
 return __r;
}

// __invariants

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
basic_string<_CharT, _Traits, _Allocator>::__invariants() const
{
 if (size() > capacity())
 return false;
 if (capacity() < __min_cap - 1)
 return false;
 if (data() == 0)
 return false;
 if (data()[size()] != value_type(0))
 return false;
 return true;
}

// operator==

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 size_t __lhs_sz = __lhs.size();
 return __lhs_sz == __rhs.size() && _Traits::compare(__lhs.data(),
 __rhs.data(),
 __lhs_sz) == 0;
}

template<class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const basic_string<char, char_traits<char>, _Allocator>& __lhs,
 const basic_string<char, char_traits<char>, _Allocator>& __rhs) _NOEXCEPT
{
 size_t __lhs_sz = __lhs.size();
 if (__lhs_sz != __rhs.size())
 return false;
 const char* __lp = __lhs.data();
 const char* __rp = __rhs.data();
 if (__lhs.__is_long())
 return char_traits<char>::compare(__lp, __rp, __lhs_sz) == 0;
 for (; __lhs_sz != 0; --__lhs_sz, ++__lp, ++__rp)
 if (*__lp != *__rp)
 return false;
 return true;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 typedef basic_string<_CharT, _Traits, _Allocator> _String;
 _LIBCPP_ASSERT(__lhs != nullptr, "operator==(char*, basic_string): received nullptr");
 size_t __lhs_len = _Traits::length(__lhs);
 if (__lhs_len != __rhs.size()) return false;
 return __rhs.compare(0, _String::npos, __lhs, __lhs_len) == 0;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const basic_string<_CharT,_Traits,_Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 typedef basic_string<_CharT, _Traits, _Allocator> _String;
 _LIBCPP_ASSERT(__rhs != nullptr, "operator==(basic_string, char*): received nullptr");
 size_t __rhs_len = _Traits::length(__rhs);
 if (__rhs_len != __lhs.size()) return false;
 return __lhs.compare(0, _String::npos, __rhs, __rhs_len) == 0;
}

// operator!=

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const basic_string<_CharT,_Traits,_Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__lhs == __rhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__lhs == __rhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 return !(__lhs == __rhs);
}

// operator<

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator< (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return __lhs.compare(__rhs) < 0;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator< (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 return __lhs.compare(__rhs) < 0;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator< (const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return __rhs.compare(__lhs) > 0;
}

// operator>

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator> (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return __rhs < __lhs;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator> (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 return __rhs < __lhs;
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator> (const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return __rhs < __lhs;
}

// operator<=

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__rhs < __lhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 return !(__rhs < __lhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__rhs < __lhs);
}

// operator>=

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__lhs < __rhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const _CharT* __rhs) _NOEXCEPT
{
 return !(__lhs < __rhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const _CharT* __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
 return !(__lhs < __rhs);
}

// operator +

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
 const basic_string<_CharT, _Traits, _Allocator>& __rhs)
{
 basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
 __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + __rhs_sz);
 __r.append(__rhs.data(), __rhs_sz);
 return __r;
}

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const _CharT* __lhs , const basic_string<_CharT,_Traits,_Allocator>& __rhs)
{
 basic_string<_CharT, _Traits, _Allocator> __r(__rhs.get_allocator());
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = _Traits::length(__lhs);
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
 __r.__init(__lhs, __lhs_sz, __lhs_sz + __rhs_sz);
 __r.append(__rhs.data(), __rhs_sz);
 return __r;
}

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Allocator>& __rhs)
{
 basic_string<_CharT, _Traits, _Allocator> __r(__rhs.get_allocator());
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
 __r.__init(&__lhs, 1, 1 + __rhs_sz);
 __r.append(__rhs.data(), __rhs_sz);
 return __r;
}

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, const _CharT* __rhs)
{
 basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = _Traits::length(__rhs);
 __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + __rhs_sz);
 __r.append(__rhs, __rhs_sz);
 return __r;
}

template<class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, _CharT __rhs)
{
 basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
 typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
 __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + 1);
 __r.push_back(__rhs);
 return __r;
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const basic_string<_CharT, _Traits, _Allocator>& __rhs)
{
 return _VSTD::move(__lhs.append(__rhs));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
{
 return _VSTD::move(__rhs.insert(0, __lhs));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
{
 return _VSTD::move(__lhs.append(__rhs));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(const _CharT* __lhs , basic_string<_CharT,_Traits,_Allocator>&& __rhs)
{
 return _VSTD::move(__rhs.insert(0, __lhs));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(_CharT __lhs, basic_string<_CharT,_Traits,_Allocator>&& __rhs)
{
 __rhs.insert(__rhs.begin(), __lhs);
 return _VSTD::move(__rhs);
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const _CharT* __rhs)
{
 return _VSTD::move(__lhs.append(__rhs));
}

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _Traits, _Allocator>
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, _CharT __rhs)
{
 __lhs.push_back(__rhs);
 return _VSTD::move(__lhs);
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

// swap

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_string<_CharT, _Traits, _Allocator>& __lhs,
 basic_string<_CharT, _Traits, _Allocator>& __rhs)
 _NOEXCEPT_(_NOEXCEPT_(__lhs.swap(__rhs)))
{
 __lhs.swap(__rhs);
}

#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS

typedef basic_string<char16_t> u16string;
typedef basic_string<char32_t> u32string;

#endif // _LIBCPP_HAS_NO_UNICODE_CHARS

_LIBCPP_FUNC_VIS int stoi (const string& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS long stol (const string& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS unsigned long stoul (const string& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS long long stoll (const string& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS unsigned long long stoull(const string& __str, size_t* __idx = 0, int __base = 10);

_LIBCPP_FUNC_VIS float stof (const string& __str, size_t* __idx = 0);
_LIBCPP_FUNC_VIS double stod (const string& __str, size_t* __idx = 0);
_LIBCPP_FUNC_VIS long double stold(const string& __str, size_t* __idx = 0);

_LIBCPP_FUNC_VIS string to_string(int __val);
_LIBCPP_FUNC_VIS string to_string(unsigned __val);
_LIBCPP_FUNC_VIS string to_string(long __val);
_LIBCPP_FUNC_VIS string to_string(unsigned long __val);
_LIBCPP_FUNC_VIS string to_string(long long __val);
_LIBCPP_FUNC_VIS string to_string(unsigned long long __val);
_LIBCPP_FUNC_VIS string to_string(float __val);
_LIBCPP_FUNC_VIS string to_string(double __val);
_LIBCPP_FUNC_VIS string to_string(long double __val);

_LIBCPP_FUNC_VIS int stoi (const wstring& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS long stol (const wstring& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS unsigned long stoul (const wstring& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS long long stoll (const wstring& __str, size_t* __idx = 0, int __base = 10);
_LIBCPP_FUNC_VIS unsigned long long stoull(const wstring& __str, size_t* __idx = 0, int __base = 10);

_LIBCPP_FUNC_VIS float stof (const wstring& __str, size_t* __idx = 0);
_LIBCPP_FUNC_VIS double stod (const wstring& __str, size_t* __idx = 0);
_LIBCPP_FUNC_VIS long double stold(const wstring& __str, size_t* __idx = 0);

_LIBCPP_FUNC_VIS wstring to_wstring(int __val);
_LIBCPP_FUNC_VIS wstring to_wstring(unsigned __val);
_LIBCPP_FUNC_VIS wstring to_wstring(long __val);
_LIBCPP_FUNC_VIS wstring to_wstring(unsigned long __val);
_LIBCPP_FUNC_VIS wstring to_wstring(long long __val);
_LIBCPP_FUNC_VIS wstring to_wstring(unsigned long long __val);
_LIBCPP_FUNC_VIS wstring to_wstring(float __val);
_LIBCPP_FUNC_VIS wstring to_wstring(double __val);
_LIBCPP_FUNC_VIS wstring to_wstring(long double __val);

template<class _CharT, class _Traits, class _Allocator>
 const typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::npos;

template<class _CharT, class _Traits, class _Allocator>
struct _LIBCPP_TYPE_VIS_ONLY hash<basic_string<_CharT, _Traits, _Allocator> >
 : public unary_function<basic_string<_CharT, _Traits, _Allocator>, size_t>
{
 size_t
 operator()(const basic_string<_CharT, _Traits, _Allocator>& __val) const _NOEXCEPT;
};

template<class _CharT, class _Traits, class _Allocator>
size_t
hash<basic_string<_CharT, _Traits, _Allocator> >::operator()(
 const basic_string<_CharT, _Traits, _Allocator>& __val) const _NOEXCEPT
{
 return __do_string_hash(__val.data(), __val.data() + __val.size());
}

template<class _CharT, class _Traits, class _Allocator>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
 const basic_string<_CharT, _Traits, _Allocator>& __str);

template<class _CharT, class _Traits, class _Allocator>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
 basic_string<_CharT, _Traits, _Allocator>& __str);

template<class _CharT, class _Traits, class _Allocator>
basic_istream<_CharT, _Traits>&
getline(basic_istream<_CharT, _Traits>& __is,
 basic_string<_CharT, _Traits, _Allocator>& __str, _CharT __dlm);

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_istream<_CharT, _Traits>&
getline(basic_istream<_CharT, _Traits>& __is,
 basic_string<_CharT, _Traits, _Allocator>& __str);

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_istream<_CharT, _Traits>&
getline(basic_istream<_CharT, _Traits>&& __is,
 basic_string<_CharT, _Traits, _Allocator>& __str, _CharT __dlm);

template<class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
basic_istream<_CharT, _Traits>&
getline(basic_istream<_CharT, _Traits>&& __is,
 basic_string<_CharT, _Traits, _Allocator>& __str);

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

#if _LIBCPP_DEBUG_LEVEL >= 2

template<class _CharT, class _Traits, class _Allocator>
bool
basic_string<_CharT, _Traits, _Allocator>::__dereferenceable(const const_iterator* __i) const
{
 return this->data() <= _VSTD::__to_raw_pointer(__i->base()) &&
 _VSTD::__to_raw_pointer(__i->base()) < this->data() + this->size();
}

template<class _CharT, class _Traits, class _Allocator>
bool
basic_string<_CharT, _Traits, _Allocator>::__decrementable(const const_iterator* __i) const
{
 return this->data() < _VSTD::__to_raw_pointer(__i->base()) &&
 _VSTD::__to_raw_pointer(__i->base()) <= this->data() + this->size();
}

template<class _CharT, class _Traits, class _Allocator>
bool
basic_string<_CharT, _Traits, _Allocator>::__addable(const const_iterator* __i, ptrdiff_t __n) const
{
 const value_type* __p = _VSTD::__to_raw_pointer(__i->base()) + __n;
 return this->data() <= __p && __p <= this->data() + this->size();
}

template<class _CharT, class _Traits, class _Allocator>
bool
basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
{
 const value_type* __p = _VSTD::__to_raw_pointer(__i->base()) + __n;
 return this->data() <= __p && __p < this->data() + this->size();
}

#endif // _LIBCPP_DEBUG_LEVEL >= 2

#if _LIBCPP_STD_VER > 11 
// Literal suffixes for basic_string [basic.string.literals]
inline namespace literals
{
 inline namespace string_literals
 {
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<char> operator "" s( const char *__str, size_t __len )
 {
 return basic_string<char> (__str, __len);
 }

 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<wchar_t> operator "" s( const wchar_t *__str, size_t __len )
 {
 return basic_string<wchar_t> (__str, __len);
 }

 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<char16_t> operator "" s( const char16_t *__str, size_t __len )
 {
 return basic_string<char16_t> (__str, __len);
 }

 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<char32_t> operator "" s( const char32_t *__str, size_t __len )
 {
 return basic_string<char32_t> (__str, __len);
 }
 }
}
#endif

_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_string<char>)
_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_string<wchar_t>)
_LIBCPP_EXTERN_TEMPLATE(string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_STRING