// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_REGEX
#define _LIBCPP_REGEX

/*
    regex synopsis

#include <compare>
#include <initializer_list>

namespace std
{

namespace regex_constants
{

enum syntax_option_type
{
    icase      = unspecified,
    nosubs     = unspecified,
    optimize   = unspecified,
    collate    = unspecified,
    ECMAScript = unspecified,
    basic      = unspecified,
    extended   = unspecified,
    awk        = unspecified,
    grep       = unspecified,
    egrep      = unspecified,
    multiline  = unspecified
};

constexpr syntax_option_type operator~(syntax_option_type f);
constexpr syntax_option_type operator&(syntax_option_type lhs, syntax_option_type rhs);
constexpr syntax_option_type operator|(syntax_option_type lhs, syntax_option_type rhs);

enum match_flag_type
{
    match_default     = 0,
    match_not_bol     = unspecified,
    match_not_eol     = unspecified,
    match_not_bow     = unspecified,
    match_not_eow     = unspecified,
    match_any         = unspecified,
    match_not_null    = unspecified,
    match_continuous  = unspecified,
    match_prev_avail  = unspecified,
    format_default    = 0,
    format_sed        = unspecified,
    format_no_copy    = unspecified,
    format_first_only = unspecified
};

constexpr match_flag_type operator~(match_flag_type f);
constexpr match_flag_type operator&(match_flag_type lhs, match_flag_type rhs);
constexpr match_flag_type operator|(match_flag_type lhs, match_flag_type rhs);

enum error_type
{
    error_collate    = unspecified,
    error_ctype      = unspecified,
    error_escape     = unspecified,
    error_backref    = unspecified,
    error_brack      = unspecified,
    error_paren      = unspecified,
    error_brace      = unspecified,
    error_badbrace   = unspecified,
    error_range      = unspecified,
    error_space      = unspecified,
    error_badrepeat  = unspecified,
    error_complexity = unspecified,
    error_stack      = unspecified
};

}  // regex_constants

class regex_error
    : public runtime_error
{
public:
    explicit regex_error(regex_constants::error_type ecode);
    regex_constants::error_type code() const;
};

template <class charT>
struct regex_traits
{
public:
    typedef charT                   char_type;
    typedef basic_string<char_type> string_type;
    typedef locale                  locale_type;
    typedef /bitmask_type/          char_class_type;

    regex_traits();

    static size_t length(const char_type* p);
    charT translate(charT c) const;
    charT translate_nocase(charT c) const;
    template <class ForwardIterator>
        string_type
        transform(ForwardIterator first, ForwardIterator last) const;
    template <class ForwardIterator>
        string_type
        transform_primary( ForwardIterator first, ForwardIterator last) const;
    template <class ForwardIterator>
        string_type
        lookup_collatename(ForwardIterator first, ForwardIterator last) const;
    template <class ForwardIterator>
        char_class_type
        lookup_classname(ForwardIterator first, ForwardIterator last,
                         bool icase = false) const;
    bool isctype(charT c, char_class_type f) const;
    int value(charT ch, int radix) const;
    locale_type imbue(locale_type l);
    locale_type getloc()const;
};

template <class charT, class traits = regex_traits<charT>>
class basic_regex
{
public:
    // types:
    typedef charT                               value_type;
    typedef traits                              traits_type;
    typedef typename traits::string_type        string_type;
    typedef regex_constants::syntax_option_type flag_type;
    typedef typename traits::locale_type        locale_type;

    // constants:
    static constexpr regex_constants::syntax_option_type icase = regex_constants::icase;
    static constexpr regex_constants::syntax_option_type nosubs = regex_constants::nosubs;
    static constexpr regex_constants::syntax_option_type optimize = regex_constants::optimize;
    static constexpr regex_constants::syntax_option_type collate = regex_constants::collate;
    static constexpr regex_constants::syntax_option_type ECMAScript = regex_constants::ECMAScript;
    static constexpr regex_constants::syntax_option_type basic = regex_constants::basic;
    static constexpr regex_constants::syntax_option_type extended = regex_constants::extended;
    static constexpr regex_constants::syntax_option_type awk = regex_constants::awk;
    static constexpr regex_constants::syntax_option_type grep = regex_constants::grep;
    static constexpr regex_constants::syntax_option_type egrep = regex_constants::egrep;
    static constexpr regex_constants::syntax_option_type multiline = regex_constants::multiline;

    // construct/copy/destroy:
    basic_regex();
    explicit basic_regex(const charT* p, flag_type f = regex_constants::ECMAScript);
    basic_regex(const charT* p, size_t len, flag_type f = regex_constants::ECMAScript);
    basic_regex(const basic_regex&);
    basic_regex(basic_regex&&) noexcept;
    template <class ST, class SA>
        explicit basic_regex(const basic_string<charT, ST, SA>& p,
                             flag_type f = regex_constants::ECMAScript);
    template <class ForwardIterator>
        basic_regex(ForwardIterator first, ForwardIterator last,
                    flag_type f = regex_constants::ECMAScript);
    basic_regex(initializer_list<charT>, flag_type = regex_constants::ECMAScript);

    ~basic_regex();

    basic_regex& operator=(const basic_regex&);
    basic_regex& operator=(basic_regex&&) noexcept;
    basic_regex& operator=(const charT* ptr);
    basic_regex& operator=(initializer_list<charT> il);
    template <class ST, class SA>
        basic_regex& operator=(const basic_string<charT, ST, SA>& p);

    // assign:
    basic_regex& assign(const basic_regex& that);
    basic_regex& assign(basic_regex&& that) noexcept;
    basic_regex& assign(const charT* ptr,           flag_type f = regex_constants::ECMAScript);
    basic_regex& assign(const charT* p, size_t len, flag_type f = regex_constants::ECMAScript);
    template <class string_traits, class A>
        basic_regex& assign(const basic_string<charT, string_traits, A>& s,
                                                    flag_type f = regex_constants::ECMAScript);
    template <class InputIterator>
        basic_regex& assign(InputIterator first, InputIterator last,
                                                    flag_type f = regex_constants::ECMAScript);
    basic_regex& assign(initializer_list<charT>,    flag_type f = regex_constants::ECMAScript);

    // const operations:
    unsigned mark_count() const;
    flag_type flags() const;

    // locale:
    locale_type imbue(locale_type loc);
    locale_type getloc() const;

    // swap:
    void swap(basic_regex&);
};

template<class ForwardIterator>
basic_regex(ForwardIterator, ForwardIterator,
            regex_constants::syntax_option_type = regex_constants::ECMAScript)
    -> basic_regex<typename iterator_traits<ForwardIterator>::value_type>; // C++17

typedef basic_regex<char>    regex;
typedef basic_regex<wchar_t> wregex;

template <class charT, class traits>
    void swap(basic_regex<charT, traits>& e1, basic_regex<charT, traits>& e2);

template <class BidirectionalIterator>
class sub_match
    : public pair<BidirectionalIterator, BidirectionalIterator>
{
public:
    typedef typename iterator_traits<BidirectionalIterator>::value_type value_type;
    typedef typename iterator_traits<BidirectionalIterator>::difference_type difference_type;
    typedef BidirectionalIterator                                      iterator;
    typedef basic_string<value_type>                                string_type;

    bool matched;

    constexpr sub_match();

    difference_type length() const;
    operator string_type() const;
    string_type str() const;

    int compare(const sub_match& s) const;
    int compare(const string_type& s) const;
    int compare(const value_type* s) const;

    void swap(sub_match& s) noexcept(see below);
};

typedef sub_match<const char*>             csub_match;
typedef sub_match<const wchar_t*>          wcsub_match;
typedef sub_match<string::const_iterator>  ssub_match;
typedef sub_match<wstring::const_iterator> wssub_match;

template <class BiIter>
    bool
    operator==(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter>
    auto
    operator<=>(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs); // Since C++20

 template <class BiIter>                                                     // Removed in C++20
    bool
    operator!=(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<=(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>=(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>(const sub_match<BiIter>& lhs, const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator==(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator!=(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator<(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator>(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool operator>=(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
                    const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator<=(const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter, class ST, class SA>
    bool
    operator==(const sub_match<BiIter>& lhs,
               const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Since C++20
    auto
    operator<=>(const sub_match<BiIter>& lhs,
                const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator!=(const sub_match<BiIter>& lhs,
               const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator<(const sub_match<BiIter>& lhs,
              const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator>(const sub_match<BiIter>& lhs,
                   const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator>=(const sub_match<BiIter>& lhs,
               const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator<=(const sub_match<BiIter>& lhs,
               const basic_string<typename iterator_traits<BiIter>::value_type, ST, SA>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator==(typename iterator_traits<BiIter>::value_type const* lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator!=(typename iterator_traits<BiIter>::value_type const* lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<(typename iterator_traits<BiIter>::value_type const* lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>(typename iterator_traits<BiIter>::value_type const* lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>=(typename iterator_traits<BiIter>::value_type const* lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<=(typename iterator_traits<BiIter>::value_type const* lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>
    bool
    operator==(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Since C++20
    auto
    operator<=>(const sub_match<BiIter>& lhs,
                typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter, class ST, class SA>                                  // Removed in C++20
    bool
    operator!=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<(const sub_match<BiIter>& lhs,
              typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>(const sub_match<BiIter>& lhs,
              typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const* rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator==(typename iterator_traits<BiIter>::value_type const& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator!=(typename iterator_traits<BiIter>::value_type const& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<(typename iterator_traits<BiIter>::value_type const& lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>(typename iterator_traits<BiIter>::value_type const& lhs,
              const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>=(typename iterator_traits<BiIter>::value_type const& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<=(typename iterator_traits<BiIter>::value_type const& lhs,
               const sub_match<BiIter>& rhs);

template <class BiIter>
    bool
    operator==(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Since C++20
    auto
    operator<=>(const sub_match<BiIter>& lhs,
                typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator!=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<(const sub_match<BiIter>& lhs,
              typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>(const sub_match<BiIter>& lhs,
              typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator>=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const& rhs);

template <class BiIter>                                                      // Removed in C++20
    bool
    operator<=(const sub_match<BiIter>& lhs,
               typename iterator_traits<BiIter>::value_type const& rhs);

template <class charT, class ST, class BiIter>
    basic_ostream<charT, ST>&
    operator<<(basic_ostream<charT, ST>& os, const sub_match<BiIter>& m);

template <class BidirectionalIterator,
          class Allocator = allocator<sub_match<BidirectionalIterator>>>
class match_results
{
public:
    typedef sub_match<BidirectionalIterator>                  value_type;
    typedef const value_type&                                 const_reference;
    typedef value_type&                                       reference;
    typedef /implementation-defined/                          const_iterator;
    typedef const_iterator                                    iterator;
    typedef typename iterator_traits<BidirectionalIterator>::difference_type difference_type;
    typedef typename allocator_traits<Allocator>::size_type   size_type;
    typedef Allocator                                         allocator_type;
    typedef typename iterator_traits<BidirectionalIterator>::value_type char_type;
    typedef basic_string<char_type>                           string_type;

    // construct/copy/destroy:
    explicit match_results(const Allocator& a = Allocator()); // before C++20
    match_results() : match_results(Allocator()) {}           // C++20
    explicit match_results(const Allocator& a);               // C++20
    match_results(const match_results& m);
    match_results(match_results&& m) noexcept;
    match_results& operator=(const match_results& m);
    match_results& operator=(match_results&& m);
    ~match_results();

    bool ready() const;

    // size:
    size_type size() const;
    size_type max_size() const;
    bool empty() const;

    // element access:
    difference_type length(size_type sub = 0) const;
    difference_type position(size_type sub = 0) const;
    string_type str(size_type sub = 0) const;
    const_reference operator[](size_type n) const;

    const_reference prefix() const;
    const_reference suffix() const;

    const_iterator begin() const;
    const_iterator end() const;
    const_iterator cbegin() const;
    const_iterator cend() const;

    // format:
    template <class OutputIter>
        OutputIter
        format(OutputIter out, const char_type* fmt_first,
               const char_type* fmt_last,
               regex_constants::match_flag_type flags = regex_constants::format_default) const;
    template <class OutputIter, class ST, class SA>
        OutputIter
        format(OutputIter out, const basic_string<char_type, ST, SA>& fmt,
               regex_constants::match_flag_type flags = regex_constants::format_default) const;
    template <class ST, class SA>
        basic_string<char_type, ST, SA>
        format(const basic_string<char_type, ST, SA>& fmt,
               regex_constants::match_flag_type flags = regex_constants::format_default) const;
    string_type
        format(const char_type* fmt,
               regex_constants::match_flag_type flags = regex_constants::format_default) const;

    // allocator:
    allocator_type get_allocator() const;

    // swap:
    void swap(match_results& that);
};

typedef match_results<const char*>             cmatch;
typedef match_results<const wchar_t*>          wcmatch;
typedef match_results<string::const_iterator>  smatch;
typedef match_results<wstring::const_iterator> wsmatch;

template <class BidirectionalIterator, class Allocator>
    bool
    operator==(const match_results<BidirectionalIterator, Allocator>& m1,
               const match_results<BidirectionalIterator, Allocator>& m2);

template <class BidirectionalIterator, class Allocator>
    bool
    operator!=(const match_results<BidirectionalIterator, Allocator>& m1,
               const match_results<BidirectionalIterator, Allocator>& m2);

template <class BidirectionalIterator, class Allocator>
    void
    swap(match_results<BidirectionalIterator, Allocator>& m1,
         match_results<BidirectionalIterator, Allocator>& m2);

template <class BidirectionalIterator, class Allocator, class charT, class traits>
    bool
    regex_match(BidirectionalIterator first, BidirectionalIterator last,
                match_results<BidirectionalIterator, Allocator>& m,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class BidirectionalIterator, class charT, class traits>
    bool
    regex_match(BidirectionalIterator first, BidirectionalIterator last,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class charT, class Allocator, class traits>
    bool
    regex_match(const charT* str, match_results<const charT*, Allocator>& m,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class Allocator, class charT, class traits>
    bool
    regex_match(const basic_string<charT, ST, SA>& s,
                match_results<typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class Allocator, class charT, class traits>
    bool
    regex_match(const basic_string<charT, ST, SA>&& s,
                match_results<typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default) = delete; // C++14

template <class charT, class traits>
    bool
    regex_match(const charT* str, const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class charT, class traits>
    bool
    regex_match(const basic_string<charT, ST, SA>& s,
                const basic_regex<charT, traits>& e,
                regex_constants::match_flag_type flags = regex_constants::match_default);

template <class BidirectionalIterator, class Allocator, class charT, class traits>
    bool
    regex_search(BidirectionalIterator first, BidirectionalIterator last,
                 match_results<BidirectionalIterator, Allocator>& m,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class BidirectionalIterator, class charT, class traits>
    bool
    regex_search(BidirectionalIterator first, BidirectionalIterator last,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class charT, class Allocator, class traits>
    bool
    regex_search(const charT* str, match_results<const charT*, Allocator>& m,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class charT, class traits>
    bool
    regex_search(const charT* str, const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class charT, class traits>
    bool
    regex_search(const basic_string<charT, ST, SA>& s,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class Allocator, class charT, class traits>
    bool
    regex_search(const basic_string<charT, ST, SA>& s,
                 match_results<typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default);

template <class ST, class SA, class Allocator, class charT, class traits>
    bool
    regex_search(const basic_string<charT, ST, SA>&& s,
                 match_results<typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m,
                 const basic_regex<charT, traits>& e,
                 regex_constants::match_flag_type flags = regex_constants::match_default) = delete; // C++14

template <class OutputIterator, class BidirectionalIterator,
          class traits, class charT, class ST, class SA>
    OutputIterator
    regex_replace(OutputIterator out,
                  BidirectionalIterator first, BidirectionalIterator last,
                  const basic_regex<charT, traits>& e,
                  const basic_string<charT, ST, SA>& fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class OutputIterator, class BidirectionalIterator,
          class traits, class charT>
    OutputIterator
    regex_replace(OutputIterator out,
                  BidirectionalIterator first, BidirectionalIterator last,
                  const basic_regex<charT, traits>& e, const charT* fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class traits, class charT, class ST, class SA, class FST, class FSA>
    basic_string<charT, ST, SA>
    regex_replace(const basic_string<charT, ST, SA>& s,
                  const basic_regex<charT, traits>& e,
                  const basic_string<charT, FST, FSA>& fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class traits, class charT, class ST, class SA>
    basic_string<charT, ST, SA>
    regex_replace(const basic_string<charT, ST, SA>& s,
                  const basic_regex<charT, traits>& e, const charT* fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class traits, class charT, class ST, class SA>
    basic_string<charT>
    regex_replace(const charT* s,
                  const basic_regex<charT, traits>& e,
                  const basic_string<charT, ST, SA>& fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class traits, class charT>
    basic_string<charT>
    regex_replace(const charT* s,
                  const basic_regex<charT, traits>& e,
                  const charT* fmt,
                  regex_constants::match_flag_type flags = regex_constants::match_default);

template <class BidirectionalIterator,
          class charT = typename iterator_traits< BidirectionalIterator>::value_type,
          class traits = regex_traits<charT>>
class regex_iterator
{
public:
    typedef basic_regex<charT, traits>           regex_type;
    typedef match_results<BidirectionalIterator> value_type;
    typedef ptrdiff_t                            difference_type;
    typedef const value_type*                    pointer;
    typedef const value_type&                    reference;
    typedef forward_iterator_tag                 iterator_category;

    regex_iterator();
    regex_iterator(BidirectionalIterator a, BidirectionalIterator b,
                   const regex_type& re,
                   regex_constants::match_flag_type m = regex_constants::match_default);
    regex_iterator(BidirectionalIterator a, BidirectionalIterator b,
                   const regex_type&& re,
                   regex_constants::match_flag_type m
                                     = regex_constants::match_default) = delete; // C++14
    regex_iterator(const regex_iterator&);
    regex_iterator& operator=(const regex_iterator&);

    bool operator==(const regex_iterator&) const;
    bool operator!=(const regex_iterator&) const;

    const value_type& operator*() const;
    const value_type* operator->() const;

    regex_iterator& operator++();
    regex_iterator operator++(int);
};

typedef regex_iterator<const char*>             cregex_iterator;
typedef regex_iterator<const wchar_t*>          wcregex_iterator;
typedef regex_iterator<string::const_iterator>  sregex_iterator;
typedef regex_iterator<wstring::const_iterator> wsregex_iterator;

template <class BidirectionalIterator,
          class charT = typename iterator_traits<BidirectionalIterator>::value_type,
          class traits = regex_traits<charT>>
class regex_token_iterator
{
public:
    typedef basic_regex<charT, traits>       regex_type;
    typedef sub_match<BidirectionalIterator> value_type;
    typedef ptrdiff_t                        difference_type;
    typedef const value_type*                pointer;
    typedef const value_type&                reference;
    typedef forward_iterator_tag             iterator_category;

    regex_token_iterator();
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type& re, int submatch = 0,
                         regex_constants::match_flag_type m = regex_constants::match_default);
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type&& re, int submatch = 0,
                         regex_constants::match_flag_type m = regex_constants::match_default) = delete; // C++14
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type& re, const vector<int>& submatches,
                         regex_constants::match_flag_type m = regex_constants::match_default);
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type&& re, const vector<int>& submatches,
                         regex_constants::match_flag_type m = regex_constants::match_default) = delete; // C++14
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type& re, initializer_list<int> submatches,
                         regex_constants::match_flag_type m = regex_constants::match_default);
    regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                         const regex_type&& re, initializer_list<int> submatches,
                         regex_constants::match_flag_type m = regex_constants::match_default) = delete; // C++14
    template <size_t N>
        regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                             const regex_type& re, const int (&submatches)[N],
                             regex_constants::match_flag_type m = regex_constants::match_default);
    template <size_t N>
        regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                             const regex_type&& re, const int (&submatches)[N],
                             regex_constants::match_flag_type m = regex_constants::match_default) = delete; // C++14
    regex_token_iterator(const regex_token_iterator&);
    regex_token_iterator& operator=(const regex_token_iterator&);

    bool operator==(const regex_token_iterator&) const;
    bool operator!=(const regex_token_iterator&) const;

    const value_type& operator*() const;
    const value_type* operator->() const;

    regex_token_iterator& operator++();
    regex_token_iterator operator++(int);
};

typedef regex_token_iterator<const char*>             cregex_token_iterator;
typedef regex_token_iterator<const wchar_t*>          wcregex_token_iterator;
typedef regex_token_iterator<string::const_iterator>  sregex_token_iterator;
typedef regex_token_iterator<wstring::const_iterator> wsregex_token_iterator;

} // std
*/

#include <__algorithm/find.h>
#include <__algorithm/search.h>
#include <__assert> // all public C++ headers provide the assertion handler
#include <__config>
#include <__iterator/back_insert_iterator.h>
#include <__iterator/wrap_iter.h>
#include <__locale>
#include <__memory_resource/polymorphic_allocator.h>
#include <__type_traits/is_swappable.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#include <__utility/swap.h>
#include <__verbose_abort>
#include <deque>
#include <stdexcept>
#include <string>
#include <vector>
#include <version>

// standard-mandated includes

// [iterator.range]
#include <__iterator/access.h>
#include <__iterator/data.h>
#include <__iterator/empty.h>
#include <__iterator/reverse_access.h>
#include <__iterator/size.h>

// [re.syn]
#include <compare>
#include <initializer_list>

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

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


#define _LIBCPP_REGEX_COMPLEXITY_FACTOR 4096

_LIBCPP_BEGIN_NAMESPACE_STD

namespace regex_constants
{

// syntax_option_type

enum syntax_option_type
{
    icase      = 1 << 0,
    nosubs     = 1 << 1,
    optimize   = 1 << 2,
    collate    = 1 << 3,
#ifdef _LIBCPP_ABI_REGEX_CONSTANTS_NONZERO
    ECMAScript = 1 << 9,
#else
    ECMAScript = 0,
#endif
    basic      = 1 << 4,
    extended   = 1 << 5,
    awk        = 1 << 6,
    grep       = 1 << 7,
    egrep      = 1 << 8,
    // 1 << 9 may be used by ECMAScript
    multiline  = 1 << 10
};

_LIBCPP_HIDE_FROM_ABI inline _LIBCPP_CONSTEXPR
syntax_option_type __get_grammar(syntax_option_type __g)
{
#ifdef _LIBCPP_ABI_REGEX_CONSTANTS_NONZERO
    return static_cast<syntax_option_type>(__g & 0x3F0);
#else
    return static_cast<syntax_option_type>(__g & 0x1F0);
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
syntax_option_type
operator~(syntax_option_type __x)
{
    return syntax_option_type(~int(__x) & 0x1FF);
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
syntax_option_type
operator&(syntax_option_type __x, syntax_option_type __y)
{
    return syntax_option_type(int(__x) & int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
syntax_option_type
operator|(syntax_option_type __x, syntax_option_type __y)
{
    return syntax_option_type(int(__x) | int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
syntax_option_type
operator^(syntax_option_type __x, syntax_option_type __y)
{
    return syntax_option_type(int(__x) ^ int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
syntax_option_type&
operator&=(syntax_option_type& __x, syntax_option_type __y)
{
    __x = __x & __y;
    return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
syntax_option_type&
operator|=(syntax_option_type& __x, syntax_option_type __y)
{
    __x = __x | __y;
    return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
syntax_option_type&
operator^=(syntax_option_type& __x, syntax_option_type __y)
{
    __x = __x ^ __y;
    return __x;
}

// match_flag_type

enum match_flag_type
{
    match_default     = 0,
    match_not_bol     = 1 << 0,
    match_not_eol     = 1 << 1,
    match_not_bow     = 1 << 2,
    match_not_eow     = 1 << 3,
    match_any         = 1 << 4,
    match_not_null    = 1 << 5,
    match_continuous  = 1 << 6,
    match_prev_avail  = 1 << 7,
    format_default    = 0,
    format_sed        = 1 << 8,
    format_no_copy    = 1 << 9,
    format_first_only = 1 << 10,
    __no_update_pos   = 1 << 11,
    __full_match      = 1 << 12
};

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
match_flag_type
operator~(match_flag_type __x)
{
    return match_flag_type(~int(__x) & 0x0FFF);
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
match_flag_type
operator&(match_flag_type __x, match_flag_type __y)
{
    return match_flag_type(int(__x) & int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
match_flag_type
operator|(match_flag_type __x, match_flag_type __y)
{
    return match_flag_type(int(__x) | int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
match_flag_type
operator^(match_flag_type __x, match_flag_type __y)
{
    return match_flag_type(int(__x) ^ int(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
match_flag_type&
operator&=(match_flag_type& __x, match_flag_type __y)
{
    __x = __x & __y;
    return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
match_flag_type&
operator|=(match_flag_type& __x, match_flag_type __y)
{
    __x = __x | __y;
    return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
match_flag_type&
operator^=(match_flag_type& __x, match_flag_type __y)
{
    __x = __x ^ __y;
    return __x;
}

enum error_type
{
    error_collate = 1,
    error_ctype,
    error_escape,
    error_backref,
    error_brack,
    error_paren,
    error_brace,
    error_badbrace,
    error_range,
    error_space,
    error_badrepeat,
    error_complexity,
    error_stack,
    __re_err_grammar,
    __re_err_empty,
    __re_err_unknown,
    __re_err_parse
};

} // namespace regex_constants

class _LIBCPP_EXCEPTION_ABI regex_error
    : public runtime_error
{
    regex_constants::error_type __code_;
public:
    explicit regex_error(regex_constants::error_type __ecode);
    _LIBCPP_HIDE_FROM_ABI regex_error(const regex_error&) _NOEXCEPT = default;
    ~regex_error() _NOEXCEPT override;
    _LIBCPP_INLINE_VISIBILITY
    regex_constants::error_type code() const {return __code_;}
};

template <regex_constants::error_type _Ev>
_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
void __throw_regex_error()
{
#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
    throw regex_error(_Ev);
#else
    _LIBCPP_VERBOSE_ABORT("regex_error was thrown in -fno-exceptions mode");
#endif
}

template <class _CharT>
struct _LIBCPP_TEMPLATE_VIS regex_traits
{
public:
    typedef _CharT                  char_type;
    typedef basic_string<char_type> string_type;
    typedef locale                  locale_type;
#if defined(__BIONIC__) || defined(_NEWLIB_VERSION)
    // Originally bionic's ctype_base used its own ctype masks because the
    // builtin ctype implementation wasn't in libc++ yet. Bionic's ctype mask
    // was only 8 bits wide and already saturated, so it used a wider type here
    // to make room for __regex_word (then a part of this class rather than
    // ctype_base). Bionic has since moved to the builtin ctype_base
    // implementation, but this was not updated to match. Since then Android has
    // needed to maintain a stable libc++ ABI, and this can't be changed without
    // an ABI break.
    // We also need this workaround for newlib since _NEWLIB_VERSION is not
    // defined yet inside __config, so we can't set the
    // _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE macro. Additionally, newlib is
    // often used for space constrained environments, so it makes sense not to
    // duplicate the ctype table.
    typedef uint16_t char_class_type;
#else
    typedef ctype_base::mask        char_class_type;
#endif

    static const char_class_type __regex_word = ctype_base::__regex_word;
private:
    locale __loc_;
    const ctype<char_type>* __ct_;
    const collate<char_type>* __col_;

public:
    regex_traits();

    _LIBCPP_INLINE_VISIBILITY
    static size_t length(const char_type* __p)
        {return char_traits<char_type>::length(__p);}
    _LIBCPP_INLINE_VISIBILITY
    char_type translate(char_type __c) const {return __c;}
    char_type translate_nocase(char_type __c) const;
    template <class _ForwardIterator>
        string_type
        transform(_ForwardIterator __f, _ForwardIterator __l) const;
    template <class _ForwardIterator>
        _LIBCPP_INLINE_VISIBILITY
        string_type
        transform_primary( _ForwardIterator __f, _ForwardIterator __l) const
            {return __transform_primary(__f, __l, char_type());}
    template <class _ForwardIterator>
        _LIBCPP_INLINE_VISIBILITY
        string_type
        lookup_collatename(_ForwardIterator __f, _ForwardIterator __l) const
            {return __lookup_collatename(__f, __l, char_type());}
    template <class _ForwardIterator>
        _LIBCPP_INLINE_VISIBILITY
        char_class_type
        lookup_classname(_ForwardIterator __f, _ForwardIterator __l,
                         bool __icase = false) const
            {return __lookup_classname(__f, __l, __icase, char_type());}
    bool isctype(char_type __c, char_class_type __m) const;
    _LIBCPP_INLINE_VISIBILITY
    int value(char_type __ch, int __radix) const
        {return __regex_traits_value(__ch, __radix);}
    locale_type imbue(locale_type __l);
    _LIBCPP_INLINE_VISIBILITY
    locale_type getloc()const {return __loc_;}

private:
    void __init();

    template <class _ForwardIterator>
        string_type
        __transform_primary(_ForwardIterator __f, _ForwardIterator __l, char) const;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    template <class _ForwardIterator>
        string_type
        __transform_primary(_ForwardIterator __f, _ForwardIterator __l, wchar_t) const;
#endif
    template <class _ForwardIterator>
        string_type
        __lookup_collatename(_ForwardIterator __f, _ForwardIterator __l, char) const;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    template <class _ForwardIterator>
        string_type
        __lookup_collatename(_ForwardIterator __f, _ForwardIterator __l, wchar_t) const;
#endif
    template <class _ForwardIterator>
        char_class_type
        __lookup_classname(_ForwardIterator __f, _ForwardIterator __l,
                           bool __icase, char) const;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    template <class _ForwardIterator>
        char_class_type
        __lookup_classname(_ForwardIterator __f, _ForwardIterator __l,
                           bool __icase, wchar_t) const;
#endif

    static int __regex_traits_value(unsigned char __ch, int __radix);
    _LIBCPP_INLINE_VISIBILITY
    int __regex_traits_value(char __ch, int __radix) const
        {return __regex_traits_value(static_cast<unsigned char>(__ch), __radix);}
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
    _LIBCPP_INLINE_VISIBILITY
    int __regex_traits_value(wchar_t __ch, int __radix) const;
#endif
};

template <class _CharT>
const typename regex_traits<_CharT>::char_class_type
regex_traits<_CharT>::__regex_word;

template <class _CharT>
regex_traits<_CharT>::regex_traits()
{
    __init();
}

template <class _CharT>
typename regex_traits<_CharT>::char_type
regex_traits<_CharT>::translate_nocase(char_type __c) const
{
    return __ct_->tolower(__c);
}

template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::string_type
regex_traits<_CharT>::transform(_ForwardIterator __f, _ForwardIterator __l) const
{
    string_type __s(__f, __l);
    return __col_->transform(__s.data(), __s.data() + __s.size());
}

template <class _CharT>
void
regex_traits<_CharT>::__init()
{
    __ct_ = &std::use_facet<ctype<char_type> >(__loc_);
    __col_ = &std::use_facet<collate<char_type> >(__loc_);
}

template <class _CharT>
typename regex_traits<_CharT>::locale_type
regex_traits<_CharT>::imbue(locale_type __l)
{
    locale __r = __loc_;
    __loc_ = __l;
    __init();
    return __r;
}

// transform_primary is very FreeBSD-specific

template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::string_type
regex_traits<_CharT>::__transform_primary(_ForwardIterator __f,
                                          _ForwardIterator __l, char) const
{
    const string_type __s(__f, __l);
    string_type __d = __col_->transform(__s.data(), __s.data() + __s.size());
    switch (__d.size())
    {
    case 1:
        break;
    case 12:
        __d[11] = __d[3];
        break;
    default:
        __d.clear();
        break;
    }
    return __d;
}

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::string_type
regex_traits<_CharT>::__transform_primary(_ForwardIterator __f,
                                          _ForwardIterator __l, wchar_t) const
{
    const string_type __s(__f, __l);
    string_type __d = __col_->transform(__s.data(), __s.data() + __s.size());
    switch (__d.size())
    {
    case 1:
        break;
    case 3:
        __d[2] = __d[0];
        break;
    default:
        __d.clear();
        break;
    }
    return __d;
}
#endif

// lookup_collatename is very FreeBSD-specific

_LIBCPP_FUNC_VIS string __get_collation_name(const char* __s);

template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::string_type
regex_traits<_CharT>::__lookup_collatename(_ForwardIterator __f,
                                           _ForwardIterator __l, char) const
{
    string_type __s(__f, __l);
    string_type __r;
    if (!__s.empty())
    {
        __r = std::__get_collation_name(__s.c_str());
        if (__r.empty() && __s.size() <= 2)
        {
            __r = __col_->transform(__s.data(), __s.data() + __s.size());
            if (__r.size() == 1 || __r.size() == 12)
                __r = __s;
            else
                __r.clear();
        }
    }
    return __r;
}

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::string_type
regex_traits<_CharT>::__lookup_collatename(_ForwardIterator __f,
                                           _ForwardIterator __l, wchar_t) const
{
    string_type __s(__f, __l);
    string __n;
    __n.reserve(__s.size());
    for (typename string_type::const_iterator __i = __s.begin(), __e = __s.end();
                                                              __i != __e; ++__i)
    {
        if (static_cast<unsigned>(*__i) >= 127)
            return string_type();
        __n.push_back(char(*__i));
    }
    string_type __r;
    if (!__s.empty())
    {
        __n = __get_collation_name(__n.c_str());
        if (!__n.empty())
            __r.assign(__n.begin(), __n.end());
        else if (__s.size() <= 2)
        {
            __r = __col_->transform(__s.data(), __s.data() + __s.size());
            if (__r.size() == 1 || __r.size() == 3)
                __r = __s;
            else
                __r.clear();
        }
    }
    return __r;
}
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

// lookup_classname

regex_traits<char>::char_class_type _LIBCPP_FUNC_VIS
__get_classname(const char* __s, bool __icase);

template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::char_class_type
regex_traits<_CharT>::__lookup_classname(_ForwardIterator __f,
                                         _ForwardIterator __l,
                                         bool __icase, char) const
{
    string_type __s(__f, __l);
    __ct_->tolower(&__s[0], &__s[0] + __s.size());
    return std::__get_classname(__s.c_str(), __icase);
}

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class _CharT>
template <class _ForwardIterator>
typename regex_traits<_CharT>::char_class_type
regex_traits<_CharT>::__lookup_classname(_ForwardIterator __f,
                                         _ForwardIterator __l,
                                         bool __icase, wchar_t) const
{
    string_type __s(__f, __l);
    __ct_->tolower(&__s[0], &__s[0] + __s.size());
    string __n;
    __n.reserve(__s.size());
    for (typename string_type::const_iterator __i = __s.begin(), __e = __s.end();
                                                              __i != __e; ++__i)
    {
        if (static_cast<unsigned>(*__i) >= 127)
            return char_class_type();
        __n.push_back(char(*__i));
    }
    return __get_classname(__n.c_str(), __icase);
}
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

template <class _CharT>
bool
regex_traits<_CharT>::isctype(char_type __c, char_class_type __m) const
{
    if (__ct_->is(__m, __c))
        return true;
    return (__c == '_' && (__m & __regex_word));
}

inline _LIBCPP_INLINE_VISIBILITY
bool __is_07(unsigned char __c)
{
    return (__c & 0xF8u) ==
#if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
        0xF0;
#else
        0x30;
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
bool __is_89(unsigned char __c)
{
    return (__c & 0xFEu) ==
#if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
        0xF8;
#else
        0x38;
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
unsigned char __to_lower(unsigned char __c)
{
#if defined(__MVS__) && !defined(__NATIVE_ASCII_F)
    return __c & 0xBF;
#else
    return __c | 0x20;
#endif
}

template <class _CharT>
int
regex_traits<_CharT>::__regex_traits_value(unsigned char __ch, int __radix)
{
    if (__is_07(__ch))  // '0' <= __ch && __ch <= '7'
        return __ch - '0';
    if (__radix != 8)
    {
        if (__is_89(__ch))  // '8' <= __ch && __ch <= '9'
            return __ch - '0';
        if (__radix == 16)
        {
            __ch = __to_lower(__ch);  // tolower
            if ('a' <= __ch && __ch <= 'f')
                return __ch - ('a' - 10);
        }
    }
    return -1;
}

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class _CharT>
inline
int
regex_traits<_CharT>::__regex_traits_value(wchar_t __ch, int __radix) const
{
    return __regex_traits_value(static_cast<unsigned char>(__ct_->narrow(__ch, char_type())), __radix);
}
#endif

template <class _CharT> class __node;

template <class _BidirectionalIterator> class _LIBCPP_TEMPLATE_VIS sub_match;

template <class _BidirectionalIterator,
          class _Allocator = allocator<sub_match<_BidirectionalIterator> > >
class _LIBCPP_TEMPLATE_VIS match_results;

template <class _CharT>
struct __state
{
    enum
    {
        __end_state = -1000,
        __consume_input,  // -999
        __begin_marked_expr, // -998
        __end_marked_expr,   // -997
        __pop_state,           // -996
        __accept_and_consume,  // -995
        __accept_but_not_consume,  // -994
        __reject,                  // -993
        __split,
        __repeat
    };

    int __do_;
    const _CharT* __first_;
    const _CharT* __current_;
    const _CharT* __last_;
    vector<sub_match<const _CharT*> > __sub_matches_;
    vector<pair<size_t, const _CharT*> > __loop_data_;
    const __node<_CharT>* __node_;
    regex_constants::match_flag_type __flags_;
    bool __at_first_;

    _LIBCPP_INLINE_VISIBILITY
    __state()
        : __do_(0), __first_(nullptr), __current_(nullptr), __last_(nullptr),
          __node_(nullptr), __flags_() {}
};

// __node

template <class _CharT>
class __node
{
    __node(const __node&);
    __node& operator=(const __node&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __node() {}
    _LIBCPP_HIDE_FROM_ABI_VIRTUAL
    virtual ~__node() {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL
    virtual void __exec(__state&) const {}
    _LIBCPP_HIDE_FROM_ABI_VIRTUAL
    virtual void __exec_split(bool, __state&) const {}
};

// __end_state

template <class _CharT>
class __end_state
    : public __node<_CharT>
{
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __end_state() {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__end_state<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__end_state;
}

// __has_one_state

template <class _CharT>
class __has_one_state
    : public __node<_CharT>
{
    __node<_CharT>* __first_;

public:
    _LIBCPP_INLINE_VISIBILITY
    explicit __has_one_state(__node<_CharT>* __s)
        : __first_(__s) {}

    _LIBCPP_INLINE_VISIBILITY
    __node<_CharT>*  first() const {return __first_;}
    _LIBCPP_INLINE_VISIBILITY
    __node<_CharT>*& first()       {return __first_;}
};

// __owns_one_state

template <class _CharT>
class __owns_one_state
    : public __has_one_state<_CharT>
{
    typedef __has_one_state<_CharT> base;

public:
    _LIBCPP_INLINE_VISIBILITY
    explicit __owns_one_state(__node<_CharT>* __s)
        : base(__s) {}

    ~__owns_one_state() override;
};

template <class _CharT>
__owns_one_state<_CharT>::~__owns_one_state()
{
    delete this->first();
}

// __empty_state

template <class _CharT>
class __empty_state
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __empty_state(__node<_CharT>* __s)
        : base(__s) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__empty_state<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    __s.__node_ = this->first();
}

// __empty_non_own_state

template <class _CharT>
class __empty_non_own_state
    : public __has_one_state<_CharT>
{
    typedef __has_one_state<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __empty_non_own_state(__node<_CharT>* __s)
        : base(__s) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__empty_non_own_state<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    __s.__node_ = this->first();
}

// __repeat_one_loop

template <class _CharT>
class __repeat_one_loop
    : public __has_one_state<_CharT>
{
    typedef __has_one_state<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __repeat_one_loop(__node<_CharT>* __s)
        : base(__s) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__repeat_one_loop<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__repeat;
    __s.__node_ = this->first();
}

// __owns_two_states

template <class _CharT>
class __owns_two_states
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    base* __second_;

public:
    _LIBCPP_INLINE_VISIBILITY
    explicit __owns_two_states(__node<_CharT>* __s1, base* __s2)
        : base(__s1), __second_(__s2) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual ~__owns_two_states();

    _LIBCPP_INLINE_VISIBILITY
    base*  second() const {return __second_;}
    _LIBCPP_INLINE_VISIBILITY
    base*& second()       {return __second_;}
};

template <class _CharT>
__owns_two_states<_CharT>::~__owns_two_states()
{
    delete __second_;
}

// __loop

template <class _CharT>
class __loop
    : public __owns_two_states<_CharT>
{
    typedef __owns_two_states<_CharT> base;

    size_t __min_;
    size_t __max_;
    unsigned __loop_id_;
    unsigned __mexp_begin_;
    unsigned __mexp_end_;
    bool __greedy_;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __loop(unsigned __loop_id,
                          __node<_CharT>* __s1, __owns_one_state<_CharT>* __s2,
                          unsigned __mexp_begin, unsigned __mexp_end,
                          bool __greedy = true,
                          size_t __min = 0,
                          size_t __max = numeric_limits<size_t>::max())
        : base(__s1, __s2), __min_(__min), __max_(__max), __loop_id_(__loop_id),
          __mexp_begin_(__mexp_begin), __mexp_end_(__mexp_end),
          __greedy_(__greedy) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state& __s) const;
    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec_split(bool __second, __state& __s) const;

private:
    _LIBCPP_INLINE_VISIBILITY
    void __init_repeat(__state& __s) const
    {
        __s.__loop_data_[__loop_id_].second = __s.__current_;
        for (size_t __i = __mexp_begin_-1; __i != __mexp_end_-1; ++__i)
        {
            __s.__sub_matches_[__i].first = __s.__last_;
            __s.__sub_matches_[__i].second = __s.__last_;
            __s.__sub_matches_[__i].matched = false;
        }
    }
};

template <class _CharT>
void
__loop<_CharT>::__exec(__state& __s) const
{
    if (__s.__do_ == __state::__repeat)
    {
        bool __do_repeat = ++__s.__loop_data_[__loop_id_].first < __max_;
        bool __do_alt = __s.__loop_data_[__loop_id_].first >= __min_;
        if (__do_repeat && __do_alt &&
                               __s.__loop_data_[__loop_id_].second == __s.__current_)
            __do_repeat = false;
        if (__do_repeat && __do_alt)
            __s.__do_ = __state::__split;
        else if (__do_repeat)
        {
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__node_ = this->first();
            __init_repeat(__s);
        }
        else
        {
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__node_ = this->second();
        }
    }
    else
    {
        __s.__loop_data_[__loop_id_].first = 0;
        bool __do_repeat = 0 < __max_;
        bool __do_alt = 0 >= __min_;
        if (__do_repeat && __do_alt)
            __s.__do_ = __state::__split;
        else if (__do_repeat)
        {
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__node_ = this->first();
            __init_repeat(__s);
        }
        else
        {
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__node_ = this->second();
        }
    }
}

template <class _CharT>
void
__loop<_CharT>::__exec_split(bool __second, __state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    if (__greedy_ != __second)
    {
        __s.__node_ = this->first();
        __init_repeat(__s);
    }
    else
        __s.__node_ = this->second();
}

// __alternate

template <class _CharT>
class __alternate
    : public __owns_two_states<_CharT>
{
    typedef __owns_two_states<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __alternate(__owns_one_state<_CharT>* __s1,
                         __owns_one_state<_CharT>* __s2)
        : base(__s1, __s2) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state& __s) const;
    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec_split(bool __second, __state& __s) const;
};

template <class _CharT>
void
__alternate<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__split;
}

template <class _CharT>
void
__alternate<_CharT>::__exec_split(bool __second, __state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    if (__second)
        __s.__node_ = this->second();
    else
        __s.__node_ = this->first();
}

// __begin_marked_subexpression

template <class _CharT>
class __begin_marked_subexpression
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    unsigned __mexp_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __begin_marked_subexpression(unsigned __mexp, __node<_CharT>* __s)
        : base(__s), __mexp_(__mexp) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__begin_marked_subexpression<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    __s.__sub_matches_[__mexp_-1].first = __s.__current_;
    __s.__node_ = this->first();
}

// __end_marked_subexpression

template <class _CharT>
class __end_marked_subexpression
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    unsigned __mexp_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __end_marked_subexpression(unsigned __mexp, __node<_CharT>* __s)
        : base(__s), __mexp_(__mexp) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__end_marked_subexpression<_CharT>::__exec(__state& __s) const
{
    __s.__do_ = __state::__accept_but_not_consume;
    __s.__sub_matches_[__mexp_-1].second = __s.__current_;
    __s.__sub_matches_[__mexp_-1].matched = true;
    __s.__node_ = this->first();
}

// __back_ref

template <class _CharT>
class __back_ref
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    unsigned __mexp_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __back_ref(unsigned __mexp, __node<_CharT>* __s)
        : base(__s), __mexp_(__mexp) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__back_ref<_CharT>::__exec(__state& __s) const
{
    if (__mexp_ > __s.__sub_matches_.size())
        __throw_regex_error<regex_constants::error_backref>();
    sub_match<const _CharT*>& __sm = __s.__sub_matches_[__mexp_-1];
    if (__sm.matched)
    {
        ptrdiff_t __len = __sm.second - __sm.first;
        if (__s.__last_ - __s.__current_ >= __len &&
            _VSTD::equal(__sm.first, __sm.second, __s.__current_))
        {
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__current_ += __len;
            __s.__node_ = this->first();
        }
        else
        {
            __s.__do_ = __state::__reject;
            __s.__node_ = nullptr;
        }
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __back_ref_icase

template <class _CharT, class _Traits>
class __back_ref_icase
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _Traits __traits_;
    unsigned __mexp_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __back_ref_icase(const _Traits& __traits, unsigned __mexp,
                              __node<_CharT>* __s)
        : base(__s), __traits_(__traits), __mexp_(__mexp) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__back_ref_icase<_CharT, _Traits>::__exec(__state& __s) const
{
    sub_match<const _CharT*>& __sm = __s.__sub_matches_[__mexp_-1];
    if (__sm.matched)
    {
        ptrdiff_t __len = __sm.second - __sm.first;
        if (__s.__last_ - __s.__current_ >= __len)
        {
            for (ptrdiff_t __i = 0; __i < __len; ++__i)
            {
                if (__traits_.translate_nocase(__sm.first[__i]) !=
                                __traits_.translate_nocase(__s.__current_[__i]))
                    goto __not_equal;
            }
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__current_ += __len;
            __s.__node_ = this->first();
        }
        else
        {
            __s.__do_ = __state::__reject;
            __s.__node_ = nullptr;
        }
    }
    else
    {
__not_equal:
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __back_ref_collate

template <class _CharT, class _Traits>
class __back_ref_collate
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _Traits __traits_;
    unsigned __mexp_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __back_ref_collate(const _Traits& __traits, unsigned __mexp,
                              __node<_CharT>* __s)
        : base(__s), __traits_(__traits), __mexp_(__mexp) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__back_ref_collate<_CharT, _Traits>::__exec(__state& __s) const
{
    sub_match<const _CharT*>& __sm = __s.__sub_matches_[__mexp_-1];
    if (__sm.matched)
    {
        ptrdiff_t __len = __sm.second - __sm.first;
        if (__s.__last_ - __s.__current_ >= __len)
        {
            for (ptrdiff_t __i = 0; __i < __len; ++__i)
            {
                if (__traits_.translate(__sm.first[__i]) !=
                                       __traits_.translate(__s.__current_[__i]))
                    goto __not_equal;
            }
            __s.__do_ = __state::__accept_but_not_consume;
            __s.__current_ += __len;
            __s.__node_ = this->first();
        }
        else
        {
            __s.__do_ = __state::__reject;
            __s.__node_ = nullptr;
        }
    }
    else
    {
__not_equal:
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __word_boundary

template <class _CharT, class _Traits>
class __word_boundary
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _Traits __traits_;
    bool __invert_;
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    explicit __word_boundary(const _Traits& __traits, bool __invert,
                             __node<_CharT>* __s)
        : base(__s), __traits_(__traits), __invert_(__invert) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__word_boundary<_CharT, _Traits>::__exec(__state& __s) const
{
    bool __is_word_b = false;
    if (__s.__first_ != __s.__last_)
    {
        if (__s.__current_ == __s.__last_)
        {
            if (!(__s.__flags_ & regex_constants::match_not_eow))
            {
                _CharT __c = __s.__current_[-1];
                __is_word_b = __c == '_' ||
                              __traits_.isctype(__c, ctype_base::alnum);
            }
        }
        else if (__s.__current_ == __s.__first_ &&
                !(__s.__flags_ & regex_constants::match_prev_avail))
        {
            if (!(__s.__flags_ & regex_constants::match_not_bow))
            {
                _CharT __c = *__s.__current_;
                __is_word_b = __c == '_' ||
                              __traits_.isctype(__c, ctype_base::alnum);
            }
        }
        else
        {
            _CharT __c1 = __s.__current_[-1];
            _CharT __c2 = *__s.__current_;
            bool __is_c1_b = __c1 == '_' ||
                             __traits_.isctype(__c1, ctype_base::alnum);
            bool __is_c2_b = __c2 == '_' ||
                             __traits_.isctype(__c2, ctype_base::alnum);
            __is_word_b = __is_c1_b != __is_c2_b;
        }
    }
    if (__is_word_b != __invert_)
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __l_anchor

template <class _CharT>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
bool __is_eol(_CharT __c)
{
    return __c == '\r' || __c == '\n';
}

template <class _CharT>
class __l_anchor_multiline
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    bool __multiline_;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __l_anchor_multiline(bool __multiline, __node<_CharT>* __s)
        : base(__s), __multiline_(__multiline) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__l_anchor_multiline<_CharT>::__exec(__state& __s) const
{
    if (__s.__at_first_ && __s.__current_ == __s.__first_ &&
        !(__s.__flags_ & regex_constants::match_not_bol))
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
    }
    else if (__multiline_ &&
             !__s.__at_first_ &&
             std::__is_eol(*_VSTD::prev(__s.__current_)))
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __r_anchor

template <class _CharT>
class __r_anchor_multiline
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    bool __multiline_;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __r_anchor_multiline(bool __multiline, __node<_CharT>* __s)
        : base(__s), __multiline_(__multiline) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__r_anchor_multiline<_CharT>::__exec(__state& __s) const
{
    if (__s.__current_ == __s.__last_ &&
        !(__s.__flags_ & regex_constants::match_not_eol))
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
    }
    else if (__multiline_ && std::__is_eol(*__s.__current_))
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __match_any

template <class _CharT>
class __match_any
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __match_any(__node<_CharT>* __s)
        : base(__s) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__match_any<_CharT>::__exec(__state& __s) const
{
    if (__s.__current_ != __s.__last_ && *__s.__current_ != 0)
    {
        __s.__do_ = __state::__accept_and_consume;
        ++__s.__current_;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __match_any_but_newline

template <class _CharT>
class __match_any_but_newline
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __match_any_but_newline(__node<_CharT>* __s)
        : base(__s) {}

    void __exec(__state&) const override;
};

template <> _LIBCPP_FUNC_VIS void __match_any_but_newline<char>::__exec(__state&) const;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <> _LIBCPP_FUNC_VIS void __match_any_but_newline<wchar_t>::__exec(__state&) const;
#endif

// __match_char

template <class _CharT>
class __match_char
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _CharT __c_;

    __match_char(const __match_char&);
    __match_char& operator=(const __match_char&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __match_char(_CharT __c, __node<_CharT>* __s)
        : base(__s), __c_(__c) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT>
void
__match_char<_CharT>::__exec(__state& __s) const
{
    if (__s.__current_ != __s.__last_ && *__s.__current_ == __c_)
    {
        __s.__do_ = __state::__accept_and_consume;
        ++__s.__current_;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __match_char_icase

template <class _CharT, class _Traits>
class __match_char_icase
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _Traits __traits_;
    _CharT __c_;

    __match_char_icase(const __match_char_icase&);
    __match_char_icase& operator=(const __match_char_icase&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __match_char_icase(const _Traits& __traits, _CharT __c, __node<_CharT>* __s)
        : base(__s), __traits_(__traits), __c_(__traits.translate_nocase(__c)) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__match_char_icase<_CharT, _Traits>::__exec(__state& __s) const
{
    if (__s.__current_ != __s.__last_ &&
        __traits_.translate_nocase(*__s.__current_) == __c_)
    {
        __s.__do_ = __state::__accept_and_consume;
        ++__s.__current_;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __match_char_collate

template <class _CharT, class _Traits>
class __match_char_collate
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    _Traits __traits_;
    _CharT __c_;

    __match_char_collate(const __match_char_collate&);
    __match_char_collate& operator=(const __match_char_collate&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __match_char_collate(const _Traits& __traits, _CharT __c, __node<_CharT>* __s)
        : base(__s), __traits_(__traits), __c_(__traits.translate(__c)) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__match_char_collate<_CharT, _Traits>::__exec(__state& __s) const
{
    if (__s.__current_ != __s.__last_ &&
        __traits_.translate(*__s.__current_) == __c_)
    {
        __s.__do_ = __state::__accept_and_consume;
        ++__s.__current_;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

// __bracket_expression

template <class _CharT, class _Traits>
class __bracket_expression
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;
    typedef typename _Traits::string_type string_type;

    _Traits __traits_;
    vector<_CharT> __chars_;
    vector<_CharT> __neg_chars_;
    vector<pair<string_type, string_type> > __ranges_;
    vector<pair<_CharT, _CharT> > __digraphs_;
    vector<string_type> __equivalences_;
    typename regex_traits<_CharT>::char_class_type __mask_;
    typename regex_traits<_CharT>::char_class_type __neg_mask_;
    bool __negate_;
    bool __icase_;
    bool __collate_;
    bool __might_have_digraph_;

    __bracket_expression(const __bracket_expression&);
    __bracket_expression& operator=(const __bracket_expression&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __bracket_expression(const _Traits& __traits, __node<_CharT>* __s,
                                 bool __negate, bool __icase, bool __collate)
        : base(__s), __traits_(__traits), __mask_(), __neg_mask_(),
          __negate_(__negate), __icase_(__icase), __collate_(__collate),
          __might_have_digraph_(__traits_.getloc().name() != "C") {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;

    _LIBCPP_INLINE_VISIBILITY
    bool __negated() const {return __negate_;}

    _LIBCPP_INLINE_VISIBILITY
    void __add_char(_CharT __c)
        {
            if (__icase_)
                __chars_.push_back(__traits_.translate_nocase(__c));
            else if (__collate_)
                __chars_.push_back(__traits_.translate(__c));
            else
                __chars_.push_back(__c);
        }
    _LIBCPP_INLINE_VISIBILITY
    void __add_neg_char(_CharT __c)
        {
            if (__icase_)
                __neg_chars_.push_back(__traits_.translate_nocase(__c));
            else if (__collate_)
                __neg_chars_.push_back(__traits_.translate(__c));
            else
                __neg_chars_.push_back(__c);
        }
    _LIBCPP_INLINE_VISIBILITY
    void __add_range(string_type __b, string_type __e)
        {
            if (__collate_)
            {
                if (__icase_)
                {
                    for (size_t __i = 0; __i < __b.size(); ++__i)
                        __b[__i] = __traits_.translate_nocase(__b[__i]);
                    for (size_t __i = 0; __i < __e.size(); ++__i)
                        __e[__i] = __traits_.translate_nocase(__e[__i]);
                }
                else
                {
                    for (size_t __i = 0; __i < __b.size(); ++__i)
                        __b[__i] = __traits_.translate(__b[__i]);
                    for (size_t __i = 0; __i < __e.size(); ++__i)
                        __e[__i] = __traits_.translate(__e[__i]);
                }
                __ranges_.push_back(std::make_pair(
                                  __traits_.transform(__b.begin(), __b.end()),
                                  __traits_.transform(__e.begin(), __e.end())));
            }
            else
            {
                if (__b.size() != 1 || __e.size() != 1)
                    __throw_regex_error<regex_constants::error_range>();
                if (__icase_)
                {
                    __b[0] = __traits_.translate_nocase(__b[0]);
                    __e[0] = __traits_.translate_nocase(__e[0]);
                }
                __ranges_.push_back(std::make_pair(_VSTD::move(__b), _VSTD::move(__e)));
            }
        }
    _LIBCPP_INLINE_VISIBILITY
    void __add_digraph(_CharT __c1, _CharT __c2)
        {
            if (__icase_)
                __digraphs_.push_back(std::make_pair(__traits_.translate_nocase(__c1),
                                                     __traits_.translate_nocase(__c2)));
            else if (__collate_)
                __digraphs_.push_back(std::make_pair(__traits_.translate(__c1),
                                                     __traits_.translate(__c2)));
            else
                __digraphs_.push_back(std::make_pair(__c1, __c2));
        }
    _LIBCPP_INLINE_VISIBILITY
    void __add_equivalence(const string_type& __s)
        {__equivalences_.push_back(__s);}
    _LIBCPP_INLINE_VISIBILITY
    void __add_class(typename regex_traits<_CharT>::char_class_type __mask)
        {__mask_ |= __mask;}
    _LIBCPP_INLINE_VISIBILITY
    void __add_neg_class(typename regex_traits<_CharT>::char_class_type __mask)
        {__neg_mask_ |= __mask;}
};

template <class _CharT, class _Traits>
void
__bracket_expression<_CharT, _Traits>::__exec(__state& __s) const
{
    bool __found = false;
    unsigned __consumed = 0;
    if (__s.__current_ != __s.__last_)
    {
        ++__consumed;
        if (__might_have_digraph_)
        {
            const _CharT* __next = _VSTD::next(__s.__current_);
            if (__next != __s.__last_)
            {
                pair<_CharT, _CharT> __ch2(*__s.__current_, *__next);
                if (__icase_)
                {
                    __ch2.first = __traits_.translate_nocase(__ch2.first);
                    __ch2.second = __traits_.translate_nocase(__ch2.second);
                }
                else if (__collate_)
                {
                    __ch2.first = __traits_.translate(__ch2.first);
                    __ch2.second = __traits_.translate(__ch2.second);
                }
                if (!__traits_.lookup_collatename(&__ch2.first, &__ch2.first+2).empty())
                {
                    // __ch2 is a digraph in this locale
                    ++__consumed;
                    for (size_t __i = 0; __i < __digraphs_.size(); ++__i)
                    {
                        if (__ch2 == __digraphs_[__i])
                        {
                            __found = true;
                            goto __exit;
                        }
                    }
                    if (__collate_ && !__ranges_.empty())
                    {
                        string_type __s2 = __traits_.transform(&__ch2.first,
                                                               &__ch2.first + 2);
                        for (size_t __i = 0; __i < __ranges_.size(); ++__i)
                        {
                            if (__ranges_[__i].first <= __s2 &&
                                __s2 <= __ranges_[__i].second)
                            {
                                __found = true;
                                goto __exit;
                            }
                        }
                    }
                    if (!__equivalences_.empty())
                    {
                        string_type __s2 = __traits_.transform_primary(&__ch2.first,
                                                                       &__ch2.first + 2);
                        for (size_t __i = 0; __i < __equivalences_.size(); ++__i)
                        {
                            if (__s2 == __equivalences_[__i])
                            {
                                __found = true;
                                goto __exit;
                            }
                        }
                    }
                    if (__traits_.isctype(__ch2.first, __mask_) &&
                        __traits_.isctype(__ch2.second, __mask_))
                    {
                        __found = true;
                        goto __exit;
                    }
                    if (!__traits_.isctype(__ch2.first, __neg_mask_) &&
                        !__traits_.isctype(__ch2.second, __neg_mask_))
                    {
                        __found = true;
                        goto __exit;
                    }
                    goto __exit;
                }
            }
        }
        // test *__s.__current_ as not a digraph
        _CharT __ch = *__s.__current_;
        if (__icase_)
            __ch = __traits_.translate_nocase(__ch);
        else if (__collate_)
            __ch = __traits_.translate(__ch);
        for (size_t __i = 0; __i < __chars_.size(); ++__i)
        {
            if (__ch == __chars_[__i])
            {
                __found = true;
                goto __exit;
            }
        }
        // When there's at least one of __neg_chars_ and __neg_mask_, the set
        // of "__found" chars is
        //   union(complement(union(__neg_chars_, __neg_mask_)),
        //         other cases...)
        //
        // It doesn't make sense to check this when there are no __neg_chars_
        // and no __neg_mask_.
        if (!(__neg_mask_ == 0 && __neg_chars_.empty()))
        {
            const bool __in_neg_mask = __traits_.isctype(__ch, __neg_mask_);
          const bool __in_neg_chars =
              _VSTD::find(__neg_chars_.begin(), __neg_chars_.end(), __ch) !=
              __neg_chars_.end();
          if (!(__in_neg_mask || __in_neg_chars))
          {
            __found = true;
            goto __exit;
          }
        }
        if (!__ranges_.empty())
        {
            string_type __s2 = __collate_ ?
                                   __traits_.transform(&__ch, &__ch + 1) :
                                   string_type(1, __ch);
            for (size_t __i = 0; __i < __ranges_.size(); ++__i)
            {
                if (__ranges_[__i].first <= __s2 && __s2 <= __ranges_[__i].second)
                {
                    __found = true;
                    goto __exit;
                }
            }
        }
        if (!__equivalences_.empty())
        {
            string_type __s2 = __traits_.transform_primary(&__ch, &__ch + 1);
            for (size_t __i = 0; __i < __equivalences_.size(); ++__i)
            {
                if (__s2 == __equivalences_[__i])
                {
                    __found = true;
                    goto __exit;
                }
            }
        }
        if (__traits_.isctype(__ch, __mask_))
        {
            __found = true;
            goto __exit;
        }
    }
    else
        __found = __negate_;  // force reject
__exit:
    if (__found != __negate_)
    {
        __s.__do_ = __state::__accept_and_consume;
        __s.__current_ += __consumed;
        __s.__node_ = this->first();
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

template <class _CharT, class _Traits> class __lookahead;

template <class _CharT, class _Traits = regex_traits<_CharT> >
    class _LIBCPP_TEMPLATE_VIS basic_regex;

typedef basic_regex<char>    regex;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef basic_regex<wchar_t> wregex;
#endif

template <class _CharT, class _Traits>
class
    _LIBCPP_TEMPLATE_VIS
    _LIBCPP_PREFERRED_NAME(regex)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wregex))
    basic_regex
{
public:
    // types:
    typedef _CharT                              value_type;
    typedef _Traits                             traits_type;
    typedef typename _Traits::string_type       string_type;
    typedef regex_constants::syntax_option_type flag_type;
    typedef typename _Traits::locale_type       locale_type;

private:
    _Traits   __traits_;
    flag_type __flags_;
    unsigned __marked_count_;
    unsigned __loop_count_;
    int __open_count_;
    shared_ptr<__empty_state<_CharT> > __start_;
    __owns_one_state<_CharT>* __end_;

    typedef _VSTD::__state<_CharT> __state;
    typedef _VSTD::__node<_CharT> __node;

public:
    // constants:
    static const regex_constants::syntax_option_type icase = regex_constants::icase;
    static const regex_constants::syntax_option_type nosubs = regex_constants::nosubs;
    static const regex_constants::syntax_option_type optimize = regex_constants::optimize;
    static const regex_constants::syntax_option_type collate = regex_constants::collate;
    static const regex_constants::syntax_option_type ECMAScript = regex_constants::ECMAScript;
    static const regex_constants::syntax_option_type basic = regex_constants::basic;
    static const regex_constants::syntax_option_type extended = regex_constants::extended;
    static const regex_constants::syntax_option_type awk = regex_constants::awk;
    static const regex_constants::syntax_option_type grep = regex_constants::grep;
    static const regex_constants::syntax_option_type egrep = regex_constants::egrep;
    static const regex_constants::syntax_option_type multiline = regex_constants::multiline;

    // construct/copy/destroy:
    _LIBCPP_INLINE_VISIBILITY
    basic_regex()
        : __flags_(regex_constants::ECMAScript), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {}
    _LIBCPP_INLINE_VISIBILITY
    explicit basic_regex(const value_type* __p, flag_type __f = regex_constants::ECMAScript)
        : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {
        __init(__p, __p + __traits_.length(__p));
        }

    _LIBCPP_INLINE_VISIBILITY
    basic_regex(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
        : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {
        __init(__p, __p + __len);
        }

//     basic_regex(const basic_regex&) = default;
//     basic_regex(basic_regex&&) = default;
    template <class _ST, class _SA>
        _LIBCPP_INLINE_VISIBILITY
        explicit basic_regex(const basic_string<value_type, _ST, _SA>& __p,
                             flag_type __f = regex_constants::ECMAScript)
        : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {
        __init(__p.begin(), __p.end());
        }

    template <class _ForwardIterator>
        _LIBCPP_INLINE_VISIBILITY
        basic_regex(_ForwardIterator __first, _ForwardIterator __last,
                    flag_type __f = regex_constants::ECMAScript)
        : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {
        __init(__first, __last);
        }
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    basic_regex(initializer_list<value_type> __il,
                flag_type __f = regex_constants::ECMAScript)
        : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
          __end_(nullptr)
        {
        __init(__il.begin(), __il.end());
        }
#endif // _LIBCPP_CXX03_LANG

//    ~basic_regex() = default;

//     basic_regex& operator=(const basic_regex&) = default;
//     basic_regex& operator=(basic_regex&&) = default;
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& operator=(const value_type* __p)
        {return assign(__p);}
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& operator=(initializer_list<value_type> __il)
        {return assign(__il);}
#endif // _LIBCPP_CXX03_LANG
    template <class _ST, class _SA>
        _LIBCPP_INLINE_VISIBILITY
        basic_regex& operator=(const basic_string<value_type, _ST, _SA>& __p)
        {return assign(__p);}

    // assign:
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& assign(const basic_regex& __that)
        {return *this = __that;}
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& assign(basic_regex&& __that) _NOEXCEPT
        {return *this = _VSTD::move(__that);}
#endif
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& assign(const value_type* __p, flag_type __f = regex_constants::ECMAScript)
        {return assign(__p, __p + __traits_.length(__p), __f);}
    _LIBCPP_INLINE_VISIBILITY
    basic_regex& assign(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
        {return assign(__p, __p + __len, __f);}
    template <class _ST, class _SA>
        _LIBCPP_INLINE_VISIBILITY
        basic_regex& assign(const basic_string<value_type, _ST, _SA>& __s,
                            flag_type __f = regex_constants::ECMAScript)
            {return assign(__s.begin(), __s.end(), __f);}

    template <class _InputIterator>
        _LIBCPP_INLINE_VISIBILITY
        typename enable_if<__is_exactly_cpp17_input_iterator<_InputIterator>::value, basic_regex&>::type
        assign(_InputIterator __first, _InputIterator __last,
                            flag_type __f = regex_constants::ECMAScript)
        {
            basic_string<_CharT> __t(__first, __last);
            return assign(__t.begin(), __t.end(), __f);
        }

private:
    _LIBCPP_INLINE_VISIBILITY
    void __member_init(flag_type __f)
    {
        __flags_ = __f;
        __marked_count_ = 0;
        __loop_count_ = 0;
        __open_count_ = 0;
        __end_ = nullptr;
    }
public:

    template <class _ForwardIterator>
        _LIBCPP_INLINE_VISIBILITY
        typename enable_if
        <
            __is_cpp17_forward_iterator<_ForwardIterator>::value,
            basic_regex&
        >::type
        assign(_ForwardIterator __first, _ForwardIterator __last,
                            flag_type __f = regex_constants::ECMAScript)
        {
            return assign(basic_regex(__first, __last, __f));
        }

#ifndef _LIBCPP_CXX03_LANG

    _LIBCPP_INLINE_VISIBILITY
    basic_regex& assign(initializer_list<value_type> __il,
                        flag_type __f = regex_constants::ECMAScript)
        {return assign(__il.begin(), __il.end(), __f);}

#endif // _LIBCPP_CXX03_LANG

    // const operations:
    _LIBCPP_INLINE_VISIBILITY
    unsigned mark_count() const {return __marked_count_;}
    _LIBCPP_INLINE_VISIBILITY
    flag_type flags() const {return __flags_;}

    // locale:
    _LIBCPP_INLINE_VISIBILITY
    locale_type imbue(locale_type __loc)
    {
        __member_init(ECMAScript);
        __start_.reset();
        return __traits_.imbue(__loc);
    }
    _LIBCPP_INLINE_VISIBILITY
    locale_type getloc() const {return __traits_.getloc();}

    // swap:
    void swap(basic_regex& __r);

private:
    _LIBCPP_INLINE_VISIBILITY
    unsigned __loop_count() const {return __loop_count_;}

    _LIBCPP_INLINE_VISIBILITY
    bool __use_multiline() const
    {
        return __get_grammar(__flags_) == ECMAScript && (__flags_ & multiline);
    }

    template <class _ForwardIterator>
        void
        __init(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_basic_reg_exp(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_RE_expression(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_simple_RE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_nondupl_RE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_one_char_or_coll_elem_RE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_Back_open_paren(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_Back_close_paren(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_Back_open_brace(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_Back_close_brace(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_BACKREF(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ORD_CHAR(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_QUOTED_CHAR(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_RE_dupl_symbol(_ForwardIterator __first, _ForwardIterator __last,
                               __owns_one_state<_CharT>* __s,
                               unsigned __mexp_begin, unsigned __mexp_end);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ERE_dupl_symbol(_ForwardIterator __first, _ForwardIterator __last,
                                __owns_one_state<_CharT>* __s,
                                unsigned __mexp_begin, unsigned __mexp_end);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_bracket_expression(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_follow_list(_ForwardIterator __first, _ForwardIterator __last,
                            __bracket_expression<_CharT, _Traits>* __ml);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_expression_term(_ForwardIterator __first, _ForwardIterator __last,
                                __bracket_expression<_CharT, _Traits>* __ml);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_equivalence_class(_ForwardIterator __first, _ForwardIterator __last,
                                  __bracket_expression<_CharT, _Traits>* __ml);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_character_class(_ForwardIterator __first, _ForwardIterator __last,
                                __bracket_expression<_CharT, _Traits>* __ml);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_collating_symbol(_ForwardIterator __first, _ForwardIterator __last,
                                 basic_string<_CharT>& __col_sym);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_DUP_COUNT(_ForwardIterator __first, _ForwardIterator __last, int& __c);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_extended_reg_exp(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ERE_branch(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ERE_expression(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_one_char_or_coll_elem_ERE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ORD_CHAR_ERE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_QUOTED_CHAR_ERE(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_ecma_exp(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_alternative(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_term(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_assertion(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_atom(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_atom_escape(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_decimal_escape(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_character_class_escape(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_character_escape(_ForwardIterator __first, _ForwardIterator __last,
                                 basic_string<_CharT>* __str = nullptr);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_pattern_character(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_grep(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_egrep(_ForwardIterator __first, _ForwardIterator __last);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_class_escape(_ForwardIterator __first, _ForwardIterator __last,
                          basic_string<_CharT>& __str,
                          __bracket_expression<_CharT, _Traits>* __ml);
    template <class _ForwardIterator>
        _ForwardIterator
        __parse_awk_escape(_ForwardIterator __first, _ForwardIterator __last,
                          basic_string<_CharT>* __str = nullptr);

    bool __test_back_ref(_CharT);

    _LIBCPP_INLINE_VISIBILITY
    void __push_l_anchor();
    void __push_r_anchor();
    void __push_match_any();
    void __push_match_any_but_newline();
    _LIBCPP_INLINE_VISIBILITY
    void __push_greedy_inf_repeat(size_t __min, __owns_one_state<_CharT>* __s,
                                  unsigned __mexp_begin = 0, unsigned __mexp_end = 0)
        {__push_loop(__min, numeric_limits<size_t>::max(), __s,
                     __mexp_begin, __mexp_end);}
    _LIBCPP_INLINE_VISIBILITY
    void __push_nongreedy_inf_repeat(size_t __min, __owns_one_state<_CharT>* __s,
                                  unsigned __mexp_begin = 0, unsigned __mexp_end = 0)
        {__push_loop(__min, numeric_limits<size_t>::max(), __s,
                     __mexp_begin, __mexp_end, false);}
    void __push_loop(size_t __min, size_t __max, __owns_one_state<_CharT>* __s,
                     size_t __mexp_begin = 0, size_t __mexp_end = 0,
                     bool __greedy = true);
    __bracket_expression<_CharT, _Traits>* __start_matching_list(bool __negate);
    void __push_char(value_type __c);
    void __push_back_ref(int __i);
    void __push_alternation(__owns_one_state<_CharT>* __sa,
                            __owns_one_state<_CharT>* __sb);
    void __push_begin_marked_subexpression();
    void __push_end_marked_subexpression(unsigned);
    void __push_empty();
    void __push_word_boundary(bool);
    void __push_lookahead(const basic_regex&, bool, unsigned);

    template <class _Allocator>
        bool
        __search(const _CharT* __first, const _CharT* __last,
                 match_results<const _CharT*, _Allocator>& __m,
                 regex_constants::match_flag_type __flags) const;

    template <class _Allocator>
        bool
        __match_at_start(const _CharT* __first, const _CharT* __last,
                 match_results<const _CharT*, _Allocator>& __m,
                 regex_constants::match_flag_type __flags, bool) const;
    template <class _Allocator>
        bool
        __match_at_start_ecma(const _CharT* __first, const _CharT* __last,
                 match_results<const _CharT*, _Allocator>& __m,
                 regex_constants::match_flag_type __flags, bool) const;
    template <class _Allocator>
        bool
        __match_at_start_posix_nosubs(const _CharT* __first, const _CharT* __last,
                 match_results<const _CharT*, _Allocator>& __m,
                 regex_constants::match_flag_type __flags, bool) const;
    template <class _Allocator>
        bool
        __match_at_start_posix_subs(const _CharT* __first, const _CharT* __last,
                 match_results<const _CharT*, _Allocator>& __m,
                 regex_constants::match_flag_type __flags, bool) const;

    template <class _Bp, class _Ap, class _Cp, class _Tp>
    friend
    bool
    regex_search(_Bp, _Bp, match_results<_Bp, _Ap>&, const basic_regex<_Cp, _Tp>&,
                 regex_constants::match_flag_type);

    template <class _Ap, class _Cp, class _Tp>
    friend
    bool
    regex_search(const _Cp*, const _Cp*, match_results<const _Cp*, _Ap>&,
                 const basic_regex<_Cp, _Tp>&, regex_constants::match_flag_type);

    template <class _Bp, class _Cp, class _Tp>
    friend
    bool
    regex_search(_Bp, _Bp, const basic_regex<_Cp, _Tp>&,
                 regex_constants::match_flag_type);

    template <class _Cp, class _Tp>
    friend
    bool
    regex_search(const _Cp*, const _Cp*,
                 const basic_regex<_Cp, _Tp>&, regex_constants::match_flag_type);

    template <class _Cp, class _Ap, class _Tp>
    friend
    bool
    regex_search(const _Cp*, match_results<const _Cp*, _Ap>&, const basic_regex<_Cp, _Tp>&,
                 regex_constants::match_flag_type);

    template <class _ST, class _SA, class _Cp, class _Tp>
    friend
    bool
    regex_search(const basic_string<_Cp, _ST, _SA>& __s,
                 const basic_regex<_Cp, _Tp>& __e,
                 regex_constants::match_flag_type __flags);

    template <class _ST, class _SA, class _Ap, class _Cp, class _Tp>
    friend
    bool
    regex_search(const basic_string<_Cp, _ST, _SA>& __s,
                 match_results<typename basic_string<_Cp, _ST, _SA>::const_iterator, _Ap>&,
                 const basic_regex<_Cp, _Tp>& __e,
                 regex_constants::match_flag_type __flags);

    template <class _Iter, class _Ap, class _Cp, class _Tp>
    friend
    bool
    regex_search(__wrap_iter<_Iter> __first,
                 __wrap_iter<_Iter> __last,
                 match_results<__wrap_iter<_Iter>, _Ap>& __m,
                 const basic_regex<_Cp, _Tp>& __e,
                 regex_constants::match_flag_type __flags);

    template <class, class> friend class __lookahead;
};

#if _LIBCPP_STD_VER >= 17
template <class _ForwardIterator,
          class = typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value, nullptr_t>::type
>
basic_regex(_ForwardIterator, _ForwardIterator,
            regex_constants::syntax_option_type = regex_constants::ECMAScript)
    -> basic_regex<typename iterator_traits<_ForwardIterator>::value_type>;
#endif

template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::icase;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::nosubs;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::optimize;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::collate;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::ECMAScript;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::basic;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::extended;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::awk;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::grep;
template <class _CharT, class _Traits>
    const regex_constants::syntax_option_type basic_regex<_CharT, _Traits>::egrep;

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::swap(basic_regex& __r)
{
    using _VSTD::swap;
    swap(__traits_, __r.__traits_);
    swap(__flags_, __r.__flags_);
    swap(__marked_count_, __r.__marked_count_);
    swap(__loop_count_, __r.__loop_count_);
    swap(__open_count_, __r.__open_count_);
    swap(__start_, __r.__start_);
    swap(__end_, __r.__end_);
}

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_regex<_CharT, _Traits>& __x, basic_regex<_CharT, _Traits>& __y)
{
    return __x.swap(__y);
}

// __lookahead

template <class _CharT, class _Traits>
class __lookahead
    : public __owns_one_state<_CharT>
{
    typedef __owns_one_state<_CharT> base;

    basic_regex<_CharT, _Traits> __exp_;
    unsigned __mexp_;
    bool __invert_;

    __lookahead(const __lookahead&);
    __lookahead& operator=(const __lookahead&);
public:
    typedef _VSTD::__state<_CharT> __state;

    _LIBCPP_INLINE_VISIBILITY
    __lookahead(const basic_regex<_CharT, _Traits>& __exp, bool __invert, __node<_CharT>* __s, unsigned __mexp)
        : base(__s), __exp_(__exp), __mexp_(__mexp), __invert_(__invert) {}

    _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
};

template <class _CharT, class _Traits>
void
__lookahead<_CharT, _Traits>::__exec(__state& __s) const
{
    match_results<const _CharT*> __m;
    __m.__init(1 + __exp_.mark_count(), __s.__current_, __s.__last_);
    bool __matched = __exp_.__match_at_start_ecma(
        __s.__current_, __s.__last_,
        __m,
        (__s.__flags_ | regex_constants::match_continuous) &
        ~regex_constants::__full_match,
        __s.__at_first_ && __s.__current_ == __s.__first_);
    if (__matched != __invert_)
    {
        __s.__do_ = __state::__accept_but_not_consume;
        __s.__node_ = this->first();
        for (unsigned __i = 1; __i < __m.size(); ++__i) {
            __s.__sub_matches_[__mexp_ + __i - 1] = __m.__matches_[__i];
        }
    }
    else
    {
        __s.__do_ = __state::__reject;
        __s.__node_ = nullptr;
    }
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
void
basic_regex<_CharT, _Traits>::__init(_ForwardIterator __first, _ForwardIterator __last)
{
    if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
    _ForwardIterator __temp = __parse(__first, __last);
    if ( __temp != __last)
        __throw_regex_error<regex_constants::__re_err_parse>();
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse(_ForwardIterator __first,
                                      _ForwardIterator __last)
{
    {
        unique_ptr<__node> __h(new __end_state<_CharT>);
        __start_.reset(new __empty_state<_CharT>(__h.get()));
        __h.release();
        __end_ = __start_.get();
    }
    switch (__get_grammar(__flags_))
    {
    case ECMAScript:
        __first = __parse_ecma_exp(__first, __last);
        break;
    case basic:
        __first = __parse_basic_reg_exp(__first, __last);
        break;
    case extended:
    case awk:
        __first = __parse_extended_reg_exp(__first, __last);
        break;
    case grep:
        __first = __parse_grep(__first, __last);
        break;
    case egrep:
        __first = __parse_egrep(__first, __last);
        break;
    default:
        __throw_regex_error<regex_constants::__re_err_grammar>();
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_basic_reg_exp(_ForwardIterator __first,
                                                    _ForwardIterator __last)
{
    if (__first != __last)
    {
        if (*__first == '^')
        {
            __push_l_anchor();
            ++__first;
        }
        if (__first != __last)
        {
            __first = __parse_RE_expression(__first, __last);
            if (__first != __last)
            {
                _ForwardIterator __temp = _VSTD::next(__first);
                if (__temp == __last && *__first == '$')
                {
                    __push_r_anchor();
                    ++__first;
                }
            }
        }
        if (__first != __last)
            __throw_regex_error<regex_constants::__re_err_empty>();
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_extended_reg_exp(_ForwardIterator __first,
                                                       _ForwardIterator __last)
{
    __owns_one_state<_CharT>* __sa = __end_;
    _ForwardIterator __temp = __parse_ERE_branch(__first, __last);
    if (__temp == __first)
        __throw_regex_error<regex_constants::__re_err_empty>();
    __first = __temp;
    while (__first != __last && *__first == '|')
    {
        __owns_one_state<_CharT>* __sb = __end_;
        __temp = __parse_ERE_branch(++__first, __last);
        if (__temp == __first)
            __throw_regex_error<regex_constants::__re_err_empty>();
        __push_alternation(__sa, __sb);
        __first = __temp;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ERE_branch(_ForwardIterator __first,
                                                 _ForwardIterator __last)
{
    _ForwardIterator __temp = __parse_ERE_expression(__first, __last);
    if (__temp == __first)
        __throw_regex_error<regex_constants::__re_err_empty>();
    do
    {
        __first = __temp;
        __temp = __parse_ERE_expression(__first, __last);
    } while (__temp != __first);
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ERE_expression(_ForwardIterator __first,
                                                     _ForwardIterator __last)
{
    __owns_one_state<_CharT>* __e = __end_;
    unsigned __mexp_begin = __marked_count_;
    _ForwardIterator __temp = __parse_one_char_or_coll_elem_ERE(__first, __last);
    if (__temp == __first && __temp != __last)
    {
        switch (*__temp)
        {
        case '^':
            __push_l_anchor();
            ++__temp;
            break;
        case '$':
            __push_r_anchor();
            ++__temp;
            break;
        case '(':
            __push_begin_marked_subexpression();
            unsigned __temp_count = __marked_count_;
            ++__open_count_;
            __temp = __parse_extended_reg_exp(++__temp, __last);
            if (__temp == __last || *__temp != ')')
                __throw_regex_error<regex_constants::error_paren>();
            __push_end_marked_subexpression(__temp_count);
            --__open_count_;
            ++__temp;
            break;
        }
    }
    if (__temp != __first)
        __temp = __parse_ERE_dupl_symbol(__temp, __last, __e, __mexp_begin+1,
                                         __marked_count_+1);
    __first = __temp;
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_RE_expression(_ForwardIterator __first,
                                                    _ForwardIterator __last)
{
    while (true)
    {
        _ForwardIterator __temp = __parse_simple_RE(__first, __last);
        if (__temp == __first)
            break;
        __first = __temp;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_simple_RE(_ForwardIterator __first,
                                                _ForwardIterator __last)
{
    if (__first != __last)
    {
        __owns_one_state<_CharT>* __e = __end_;
        unsigned __mexp_begin = __marked_count_;
        _ForwardIterator __temp = __parse_nondupl_RE(__first, __last);
        if (__temp != __first)
            __first = __parse_RE_dupl_symbol(__temp, __last, __e,
                                             __mexp_begin+1, __marked_count_+1);
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_nondupl_RE(_ForwardIterator __first,
                                                 _ForwardIterator __last)
{
    _ForwardIterator __temp = __first;
    __first = __parse_one_char_or_coll_elem_RE(__first, __last);
    if (__temp == __first)
    {
        __temp = __parse_Back_open_paren(__first, __last);
        if (__temp != __first)
        {
            __push_begin_marked_subexpression();
            unsigned __temp_count = __marked_count_;
            __first = __parse_RE_expression(__temp, __last);
            __temp = __parse_Back_close_paren(__first, __last);
            if (__temp == __first)
                __throw_regex_error<regex_constants::error_paren>();
            __push_end_marked_subexpression(__temp_count);
            __first = __temp;
        }
        else
            __first = __parse_BACKREF(__first, __last);
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_one_char_or_coll_elem_RE(
                                                       _ForwardIterator __first,
                                                       _ForwardIterator __last)
{
    _ForwardIterator __temp = __parse_ORD_CHAR(__first, __last);
    if (__temp == __first)
    {
        __temp = __parse_QUOTED_CHAR(__first, __last);
        if (__temp == __first)
        {
            if (__temp != __last && *__temp == '.')
            {
                __push_match_any();
                ++__temp;
            }
            else
                __temp = __parse_bracket_expression(__first, __last);
        }
    }
    __first = __temp;
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_one_char_or_coll_elem_ERE(
                                                       _ForwardIterator __first,
                                                       _ForwardIterator __last)
{
    _ForwardIterator __temp = __parse_ORD_CHAR_ERE(__first, __last);
    if (__temp == __first)
    {
        __temp = __parse_QUOTED_CHAR_ERE(__first, __last);
        if (__temp == __first)
        {
            if (__temp != __last && *__temp == '.')
            {
                __push_match_any();
                ++__temp;
            }
            else
                __temp = __parse_bracket_expression(__first, __last);
        }
    }
    __first = __temp;
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_Back_open_paren(_ForwardIterator __first,
                                                      _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\' && *__temp == '(')
                __first = ++__temp;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_Back_close_paren(_ForwardIterator __first,
                                                       _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\' && *__temp == ')')
                __first = ++__temp;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_Back_open_brace(_ForwardIterator __first,
                                                      _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\' && *__temp == '{')
                __first = ++__temp;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_Back_close_brace(_ForwardIterator __first,
                                                       _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\' && *__temp == '}')
                __first = ++__temp;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_BACKREF(_ForwardIterator __first,
                                              _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last && *__first == '\\' && __test_back_ref(*__temp))
            __first = ++__temp;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ORD_CHAR(_ForwardIterator __first,
                                               _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp == __last && *__first == '$')
            return __first;
        // Not called inside a bracket
        if (*__first == '.' || *__first == '\\' || *__first == '[')
            return __first;
        __push_char(*__first);
        ++__first;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ORD_CHAR_ERE(_ForwardIterator __first,
                                                   _ForwardIterator __last)
{
    if (__first != __last)
    {
        switch (*__first)
        {
        case '^':
        case '.':
        case '[':
        case '$':
        case '(':
        case '|':
        case '*':
        case '+':
        case '?':
        case '{':
        case '\\':
            break;
        case ')':
            if (__open_count_ == 0)
            {
                __push_char(*__first);
                ++__first;
            }
            break;
        default:
            __push_char(*__first);
            ++__first;
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_QUOTED_CHAR(_ForwardIterator __first,
                                                  _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\')
            {
                switch (*__temp)
                {
                case '^':
                case '.':
                case '*':
                case '[':
                case '$':
                case '\\':
                    __push_char(*__temp);
                    __first = ++__temp;
                    break;
                }
            }
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_QUOTED_CHAR_ERE(_ForwardIterator __first,
                                                      _ForwardIterator __last)
{
    if (__first != __last)
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        if (__temp != __last)
        {
            if (*__first == '\\')
            {
                switch (*__temp)
                {
                case '^':
                case '.':
                case '*':
                case '[':
                case '$':
                case '\\':
                case '(':
                case ')':
                case '|':
                case '+':
                case '?':
                case '{':
                case '}':
                    __push_char(*__temp);
                    __first = ++__temp;
                    break;
                default:
                    if (__get_grammar(__flags_) == awk)
                        __first = __parse_awk_escape(++__first, __last);
                    else if(__test_back_ref(*__temp))
                        __first = ++__temp;
                    break;
                }
            }
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_RE_dupl_symbol(_ForwardIterator __first,
                                                     _ForwardIterator __last,
                                                     __owns_one_state<_CharT>* __s,
                                                     unsigned __mexp_begin,
                                                     unsigned __mexp_end)
{
    if (__first != __last)
    {
        if (*__first == '*')
        {
            __push_greedy_inf_repeat(0, __s, __mexp_begin, __mexp_end);
            ++__first;
        }
        else
        {
            _ForwardIterator __temp = __parse_Back_open_brace(__first, __last);
            if (__temp != __first)
            {
                int __min = 0;
                __first = __temp;
                __temp = __parse_DUP_COUNT(__first, __last, __min);
                if (__temp == __first)
                    __throw_regex_error<regex_constants::error_badbrace>();
                __first = __temp;
                if (__first == __last)
                    __throw_regex_error<regex_constants::error_brace>();
                if (*__first != ',')
                {
                    __temp = __parse_Back_close_brace(__first, __last);
                    if (__temp == __first)
                        __throw_regex_error<regex_constants::error_brace>();
                    __push_loop(__min, __min, __s, __mexp_begin, __mexp_end,
                                    true);
                    __first = __temp;
                }
                else
                {
                    ++__first;  // consume ','
                    int __max = -1;
                    __first = __parse_DUP_COUNT(__first, __last, __max);
                    __temp = __parse_Back_close_brace(__first, __last);
                    if (__temp == __first)
                        __throw_regex_error<regex_constants::error_brace>();
                    if (__max == -1)
                        __push_greedy_inf_repeat(__min, __s, __mexp_begin, __mexp_end);
                    else
                    {
                        if (__max < __min)
                            __throw_regex_error<regex_constants::error_badbrace>();
                        __push_loop(__min, __max, __s, __mexp_begin, __mexp_end,
                                    true);
                    }
                    __first = __temp;
                }
            }
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ERE_dupl_symbol(_ForwardIterator __first,
                                                      _ForwardIterator __last,
                                                      __owns_one_state<_CharT>* __s,
                                                      unsigned __mexp_begin,
                                                      unsigned __mexp_end)
{
    if (__first != __last)
    {
        unsigned __grammar = __get_grammar(__flags_);
        switch (*__first)
        {
        case '*':
            ++__first;
            if (__grammar == ECMAScript && __first != __last && *__first == '?')
            {
                ++__first;
                __push_nongreedy_inf_repeat(0, __s, __mexp_begin, __mexp_end);
            }
            else
                __push_greedy_inf_repeat(0, __s, __mexp_begin, __mexp_end);
            break;
        case '+':
            ++__first;
            if (__grammar == ECMAScript && __first != __last && *__first == '?')
            {
                ++__first;
                __push_nongreedy_inf_repeat(1, __s, __mexp_begin, __mexp_end);
            }
            else
                __push_greedy_inf_repeat(1, __s, __mexp_begin, __mexp_end);
            break;
        case '?':
            ++__first;
            if (__grammar == ECMAScript && __first != __last && *__first == '?')
            {
                ++__first;
                __push_loop(0, 1, __s, __mexp_begin, __mexp_end, false);
            }
            else
                __push_loop(0, 1, __s, __mexp_begin, __mexp_end);
            break;
        case '{':
            {
                int __min;
                _ForwardIterator __temp = __parse_DUP_COUNT(++__first, __last, __min);
                if (__temp == __first)
                    __throw_regex_error<regex_constants::error_badbrace>();
                __first = __temp;
                if (__first == __last)
                    __throw_regex_error<regex_constants::error_brace>();
                switch (*__first)
                {
                case '}':
                    ++__first;
                    if (__grammar == ECMAScript && __first != __last && *__first == '?')
                    {
                        ++__first;
                        __push_loop(__min, __min, __s, __mexp_begin, __mexp_end, false);
                    }
                    else
                        __push_loop(__min, __min, __s, __mexp_begin, __mexp_end);
                    break;
                case ',':
                    ++__first;
                    if (__first == __last)
                        __throw_regex_error<regex_constants::error_badbrace>();
                    if (*__first == '}')
                    {
                        ++__first;
                        if (__grammar == ECMAScript && __first != __last && *__first == '?')
                        {
                            ++__first;
                            __push_nongreedy_inf_repeat(__min, __s, __mexp_begin, __mexp_end);
                        }
                        else
                            __push_greedy_inf_repeat(__min, __s, __mexp_begin, __mexp_end);
                    }
                    else
                    {
                        int __max = -1;
                        __temp = __parse_DUP_COUNT(__first, __last, __max);
                        if (__temp == __first)
                            __throw_regex_error<regex_constants::error_brace>();
                        __first = __temp;
                        if (__first == __last || *__first != '}')
                            __throw_regex_error<regex_constants::error_brace>();
                        ++__first;
                        if (__max < __min)
                            __throw_regex_error<regex_constants::error_badbrace>();
                        if (__grammar == ECMAScript && __first != __last && *__first == '?')
                        {
                            ++__first;
                            __push_loop(__min, __max, __s, __mexp_begin, __mexp_end, false);
                        }
                        else
                            __push_loop(__min, __max, __s, __mexp_begin, __mexp_end);
                    }
                    break;
                default:
                    __throw_regex_error<regex_constants::error_badbrace>();
                }
            }
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_bracket_expression(_ForwardIterator __first,
                                                         _ForwardIterator __last)
{
    if (__first != __last && *__first == '[')
    {
        ++__first;
        if (__first == __last)
            __throw_regex_error<regex_constants::error_brack>();
        bool __negate = false;
        if (*__first == '^')
        {
            ++__first;
            __negate = true;
        }
        __bracket_expression<_CharT, _Traits>* __ml = __start_matching_list(__negate);
        // __ml owned by *this
        if (__first == __last)
            __throw_regex_error<regex_constants::error_brack>();
        if (__get_grammar(__flags_) != ECMAScript && *__first == ']')
        {
            __ml->__add_char(']');
            ++__first;
        }
        __first = __parse_follow_list(__first, __last, __ml);
        if (__first == __last)
            __throw_regex_error<regex_constants::error_brack>();
        if (*__first == '-')
        {
            __ml->__add_char('-');
            ++__first;
        }
        if (__first == __last || *__first != ']')
            __throw_regex_error<regex_constants::error_brack>();
        ++__first;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_follow_list(_ForwardIterator __first,
                                    _ForwardIterator __last,
                                    __bracket_expression<_CharT, _Traits>* __ml)
{
    if (__first != __last)
    {
        while (true)
        {
            _ForwardIterator __temp = __parse_expression_term(__first, __last,
                                                              __ml);
            if (__temp == __first)
                break;
            __first = __temp;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_expression_term(_ForwardIterator __first,
                                    _ForwardIterator __last,
                                    __bracket_expression<_CharT, _Traits>* __ml)
{
    if (__first != __last && *__first != ']')
    {
        _ForwardIterator __temp = _VSTD::next(__first);
        basic_string<_CharT> __start_range;
        if (__temp != __last && *__first == '[')
        {
            if (*__temp == '=')
                return __parse_equivalence_class(++__temp, __last, __ml);
            else if (*__temp == ':')
                return __parse_character_class(++__temp, __last, __ml);
            else if (*__temp == '.')
                __first = __parse_collating_symbol(++__temp, __last, __start_range);
        }
        unsigned __grammar = __get_grammar(__flags_);
        if (__start_range.empty())
        {
            if ((__grammar == ECMAScript || __grammar == awk) && *__first == '\\')
            {
                if (__grammar == ECMAScript)
                    __first = __parse_class_escape(++__first, __last, __start_range, __ml);
                else
                    __first = __parse_awk_escape(++__first, __last, &__start_range);
            }
            else
            {
                __start_range = *__first;
                ++__first;
            }
        }
        if (__first != __last && *__first != ']')
        {
            __temp = _VSTD::next(__first);
            if (__temp != __last && *__first == '-' && *__temp != ']')
            {
                // parse a range
                basic_string<_CharT> __end_range;
                __first = __temp;
                ++__temp;
                if (__temp != __last && *__first == '[' && *__temp == '.')
                    __first = __parse_collating_symbol(++__temp, __last, __end_range);
                else
                {
                    if ((__grammar == ECMAScript || __grammar == awk) && *__first == '\\')
                    {
                        if (__grammar == ECMAScript)
                            __first = __parse_class_escape(++__first, __last,
                                                           __end_range, __ml);
                        else
                            __first = __parse_awk_escape(++__first, __last,
                                                         &__end_range);
                    }
                    else
                    {
                        __end_range = *__first;
                        ++__first;
                    }
                }
                __ml->__add_range(_VSTD::move(__start_range), _VSTD::move(__end_range));
            }
            else if (!__start_range.empty())
            {
                if (__start_range.size() == 1)
                    __ml->__add_char(__start_range[0]);
                else
                    __ml->__add_digraph(__start_range[0], __start_range[1]);
            }
        }
        else if (!__start_range.empty())
        {
            if (__start_range.size() == 1)
                __ml->__add_char(__start_range[0]);
            else
                __ml->__add_digraph(__start_range[0], __start_range[1]);
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_class_escape(_ForwardIterator __first,
                          _ForwardIterator __last,
                          basic_string<_CharT>& __str,
                          __bracket_expression<_CharT, _Traits>* __ml)
{
    if (__first == __last)
        __throw_regex_error<regex_constants::error_escape>();
    switch (*__first)
    {
    case 0:
        __str = *__first;
        return ++__first;
    case 'b':
        __str = _CharT(8);
        return ++__first;
    case 'd':
        __ml->__add_class(ctype_base::digit);
        return ++__first;
    case 'D':
        __ml->__add_neg_class(ctype_base::digit);
        return ++__first;
    case 's':
        __ml->__add_class(ctype_base::space);
        return ++__first;
    case 'S':
        __ml->__add_neg_class(ctype_base::space);
        return ++__first;
    case 'w':
        __ml->__add_class(ctype_base::alnum);
        __ml->__add_char('_');
        return ++__first;
    case 'W':
        __ml->__add_neg_class(ctype_base::alnum);
        __ml->__add_neg_char('_');
        return ++__first;
    }
    __first = __parse_character_escape(__first, __last, &__str);
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_awk_escape(_ForwardIterator __first,
                          _ForwardIterator __last,
                          basic_string<_CharT>* __str)
{
    if (__first == __last)
        __throw_regex_error<regex_constants::error_escape>();
    switch (*__first)
    {
    case '\\':
    case '"':
    case '/':
        if (__str)
            *__str = *__first;
        else
            __push_char(*__first);
        return ++__first;
    case 'a':
        if (__str)
            *__str = _CharT(7);
        else
            __push_char(_CharT(7));
        return ++__first;
    case 'b':
        if (__str)
            *__str = _CharT(8);
        else
            __push_char(_CharT(8));
        return ++__first;
    case 'f':
        if (__str)
            *__str = _CharT(0xC);
        else
            __push_char(_CharT(0xC));
        return ++__first;
    case 'n':
        if (__str)
            *__str = _CharT(0xA);
        else
            __push_char(_CharT(0xA));
        return ++__first;
    case 'r':
        if (__str)
            *__str = _CharT(0xD);
        else
            __push_char(_CharT(0xD));
        return ++__first;
    case 't':
        if (__str)
            *__str = _CharT(0x9);
        else
            __push_char(_CharT(0x9));
        return ++__first;
    case 'v':
        if (__str)
            *__str = _CharT(0xB);
        else
            __push_char(_CharT(0xB));
        return ++__first;
    }
    if ('0' <= *__first && *__first <= '7')
    {
        unsigned __val = *__first - '0';
        if (++__first != __last && ('0' <= *__first && *__first <= '7'))
        {
            __val = 8 * __val + *__first - '0';
            if (++__first != __last && ('0' <= *__first && *__first <= '7'))
                __val = 8 * __val + *__first++ - '0';
        }
        if (__str)
            *__str = _CharT(__val);
        else
            __push_char(_CharT(__val));
    }
    else
        __throw_regex_error<regex_constants::error_escape>();
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_equivalence_class(_ForwardIterator __first,
                                    _ForwardIterator __last,
                                    __bracket_expression<_CharT, _Traits>* __ml)
{
    // Found [=
    //   This means =] must exist
    value_type __equal_close[2] = {'=', ']'};
    _ForwardIterator __temp = _VSTD::search(__first, __last, __equal_close,
                                                            __equal_close+2);
    if (__temp == __last)
        __throw_regex_error<regex_constants::error_brack>();
    // [__first, __temp) contains all text in [= ... =]
    string_type __collate_name =
        __traits_.lookup_collatename(__first, __temp);
    if (__collate_name.empty())
        __throw_regex_error<regex_constants::error_collate>();
    string_type __equiv_name =
        __traits_.transform_primary(__collate_name.begin(),
                                    __collate_name.end());
    if (!__equiv_name.empty())
        __ml->__add_equivalence(__equiv_name);
    else
    {
        switch (__collate_name.size())
        {
        case 1:
            __ml->__add_char(__collate_name[0]);
            break;
        case 2:
            __ml->__add_digraph(__collate_name[0], __collate_name[1]);
            break;
        default:
            __throw_regex_error<regex_constants::error_collate>();
        }
    }
    __first = _VSTD::next(__temp, 2);
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_character_class(_ForwardIterator __first,
                                    _ForwardIterator __last,
                                    __bracket_expression<_CharT, _Traits>* __ml)
{
    // Found [:
    //   This means :] must exist
    value_type __colon_close[2] = {':', ']'};
    _ForwardIterator __temp = _VSTD::search(__first, __last, __colon_close,
                                                            __colon_close+2);
    if (__temp == __last)
        __throw_regex_error<regex_constants::error_brack>();
    // [__first, __temp) contains all text in [: ... :]
    typedef typename _Traits::char_class_type char_class_type;
    char_class_type __class_type =
        __traits_.lookup_classname(__first, __temp, __flags_ & icase);
    if (__class_type == 0)
        __throw_regex_error<regex_constants::error_ctype>();
    __ml->__add_class(__class_type);
    __first = _VSTD::next(__temp, 2);
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_collating_symbol(_ForwardIterator __first,
                                                _ForwardIterator __last,
                                                basic_string<_CharT>& __col_sym)
{
    // Found [.
    //   This means .] must exist
    value_type __dot_close[2] = {'.', ']'};
    _ForwardIterator __temp = _VSTD::search(__first, __last, __dot_close,
                                                            __dot_close+2);
    if (__temp == __last)
        __throw_regex_error<regex_constants::error_brack>();
    // [__first, __temp) contains all text in [. ... .]
    __col_sym = __traits_.lookup_collatename(__first, __temp);
    switch (__col_sym.size())
    {
    case 1:
    case 2:
        break;
    default:
        __throw_regex_error<regex_constants::error_collate>();
    }
    __first = _VSTD::next(__temp, 2);
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_DUP_COUNT(_ForwardIterator __first,
                                                _ForwardIterator __last,
                                                int& __c)
{
    if (__first != __last )
    {
        int __val = __traits_.value(*__first, 10);
        if ( __val != -1 )
        {
            __c = __val;
            for (++__first;
                 __first != __last && ( __val = __traits_.value(*__first, 10)) != -1;
                 ++__first)
            {
                if (__c >= numeric_limits<int>::max() / 10)
                    __throw_regex_error<regex_constants::error_badbrace>();
                __c *= 10;
                __c += __val;
            }
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_ecma_exp(_ForwardIterator __first,
                                               _ForwardIterator __last)
{
    __owns_one_state<_CharT>* __sa = __end_;
    _ForwardIterator __temp = __parse_alternative(__first, __last);
    if (__temp == __first)
        __push_empty();
    __first = __temp;
    while (__first != __last && *__first == '|')
    {
        __owns_one_state<_CharT>* __sb = __end_;
        __temp = __parse_alternative(++__first, __last);
        if (__temp == __first)
            __push_empty();
        __push_alternation(__sa, __sb);
        __first = __temp;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_alternative(_ForwardIterator __first,
                                                  _ForwardIterator __last)
{
    while (true)
    {
        _ForwardIterator __temp = __parse_term(__first, __last);
        if (__temp == __first)
            break;
        __first = __temp;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_term(_ForwardIterator __first,
                                           _ForwardIterator __last)
{
    _ForwardIterator __temp = __parse_assertion(__first, __last);
    if (__temp == __first)
    {
        __owns_one_state<_CharT>* __e = __end_;
        unsigned __mexp_begin = __marked_count_;
        __temp = __parse_atom(__first, __last);
        if (__temp != __first)
            __first = __parse_ERE_dupl_symbol(__temp, __last, __e,
                                              __mexp_begin+1, __marked_count_+1);
    }
    else
        __first = __temp;
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_assertion(_ForwardIterator __first,
                                                _ForwardIterator __last)
{
    if (__first != __last)
    {
        switch (*__first)
        {
        case '^':
            __push_l_anchor();
            ++__first;
            break;
        case '$':
            __push_r_anchor();
            ++__first;
            break;
        case '\\':
            {
                _ForwardIterator __temp = _VSTD::next(__first);
                if (__temp != __last)
                {
                    if (*__temp == 'b')
                    {
                        __push_word_boundary(false);
                        __first = ++__temp;
                    }
                    else if (*__temp == 'B')
                    {
                        __push_word_boundary(true);
                        __first = ++__temp;
                    }
                }
            }
            break;
        case '(':
            {
                _ForwardIterator __temp = _VSTD::next(__first);
                if (__temp != __last && *__temp == '?')
                {
                    if (++__temp != __last)
                    {
                        switch (*__temp)
                        {
                        case '=':
                            {
                                basic_regex __exp;
                                __exp.__flags_ = __flags_;
                                __temp = __exp.__parse(++__temp, __last);
                                unsigned __mexp = __exp.__marked_count_;
                                __push_lookahead(_VSTD::move(__exp), false, __marked_count_);
                                __marked_count_ += __mexp;
                                if (__temp == __last || *__temp != ')')
                                    __throw_regex_error<regex_constants::error_paren>();
                                __first = ++__temp;
                            }
                            break;
                        case '!':
                            {
                                basic_regex __exp;
                                __exp.__flags_ = __flags_;
                                __temp = __exp.__parse(++__temp, __last);
                                unsigned __mexp = __exp.__marked_count_;
                                __push_lookahead(_VSTD::move(__exp), true, __marked_count_);
                                __marked_count_ += __mexp;
                                if (__temp == __last || *__temp != ')')
                                    __throw_regex_error<regex_constants::error_paren>();
                                __first = ++__temp;
                            }
                            break;
                        }
                    }
                }
            }
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_atom(_ForwardIterator __first,
                                           _ForwardIterator __last)
{
    if (__first != __last)
    {
        switch (*__first)
        {
        case '.':
            __push_match_any_but_newline();
            ++__first;
            break;
        case '\\':
            __first = __parse_atom_escape(__first, __last);
            break;
        case '[':
            __first = __parse_bracket_expression(__first, __last);
            break;
        case '(':
            {
                ++__first;
                if (__first == __last)
                    __throw_regex_error<regex_constants::error_paren>();
                _ForwardIterator __temp = _VSTD::next(__first);
                if (__temp != __last && *__first == '?' && *__temp == ':')
                {
                    ++__open_count_;
                    __first = __parse_ecma_exp(++__temp, __last);
                    if (__first == __last || *__first != ')')
                        __throw_regex_error<regex_constants::error_paren>();
                    --__open_count_;
                    ++__first;
                }
                else
                {
                    __push_begin_marked_subexpression();
                    unsigned __temp_count = __marked_count_;
                    ++__open_count_;
                    __first = __parse_ecma_exp(__first, __last);
                    if (__first == __last || *__first != ')')
                        __throw_regex_error<regex_constants::error_paren>();
                    __push_end_marked_subexpression(__temp_count);
                    --__open_count_;
                    ++__first;
                }
            }
            break;
        case '*':
        case '+':
        case '?':
        case '{':
            __throw_regex_error<regex_constants::error_badrepeat>();
            break;
        default:
            __first = __parse_pattern_character(__first, __last);
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_atom_escape(_ForwardIterator __first,
                                                  _ForwardIterator __last)
{
    if (__first != __last && *__first == '\\')
    {
        _ForwardIterator __t1 = _VSTD::next(__first);
        if (__t1 == __last)
            __throw_regex_error<regex_constants::error_escape>();

        _ForwardIterator __t2 = __parse_decimal_escape(__t1, __last);
        if (__t2 != __t1)
            __first = __t2;
        else
        {
            __t2 = __parse_character_class_escape(__t1, __last);
            if (__t2 != __t1)
                __first = __t2;
            else
            {
                __t2 = __parse_character_escape(__t1, __last);
                if (__t2 != __t1)
                    __first = __t2;
            }
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_decimal_escape(_ForwardIterator __first,
                                                     _ForwardIterator __last)
{
    if (__first != __last)
    {
        if (*__first == '0')
        {
            __push_char(_CharT());
            ++__first;
        }
        else if ('1' <= *__first && *__first <= '9')
        {
            unsigned __v = *__first - '0';
            for (++__first;
                    __first != __last && '0' <= *__first && *__first <= '9'; ++__first)
                {
                if (__v >= numeric_limits<unsigned>::max() / 10)
                    __throw_regex_error<regex_constants::error_backref>();
                __v = 10 * __v + *__first - '0';
                }
            if (__v == 0 || __v > mark_count())
                __throw_regex_error<regex_constants::error_backref>();
            __push_back_ref(__v);
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_character_class_escape(_ForwardIterator __first,
                                                             _ForwardIterator __last)
{
    if (__first != __last)
    {
        __bracket_expression<_CharT, _Traits>* __ml;
        switch (*__first)
        {
        case 'd':
            __ml = __start_matching_list(false);
            __ml->__add_class(ctype_base::digit);
            ++__first;
            break;
        case 'D':
            __ml = __start_matching_list(true);
            __ml->__add_class(ctype_base::digit);
            ++__first;
            break;
        case 's':
            __ml = __start_matching_list(false);
            __ml->__add_class(ctype_base::space);
            ++__first;
            break;
        case 'S':
            __ml = __start_matching_list(true);
            __ml->__add_class(ctype_base::space);
            ++__first;
            break;
        case 'w':
            __ml = __start_matching_list(false);
            __ml->__add_class(ctype_base::alnum);
            __ml->__add_char('_');
            ++__first;
            break;
        case 'W':
            __ml = __start_matching_list(true);
            __ml->__add_class(ctype_base::alnum);
            __ml->__add_char('_');
            ++__first;
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_character_escape(_ForwardIterator __first,
                                                    _ForwardIterator __last,
                                                    basic_string<_CharT>* __str)
{
    if (__first != __last)
    {
        _ForwardIterator __t;
        unsigned __sum = 0;
        int __hd;
        switch (*__first)
        {
        case 'f':
            if (__str)
                *__str = _CharT(0xC);
            else
                __push_char(_CharT(0xC));
            ++__first;
            break;
        case 'n':
            if (__str)
                *__str = _CharT(0xA);
            else
                __push_char(_CharT(0xA));
            ++__first;
            break;
        case 'r':
            if (__str)
                *__str = _CharT(0xD);
            else
                __push_char(_CharT(0xD));
            ++__first;
            break;
        case 't':
            if (__str)
                *__str = _CharT(0x9);
            else
                __push_char(_CharT(0x9));
            ++__first;
            break;
        case 'v':
            if (__str)
                *__str = _CharT(0xB);
            else
                __push_char(_CharT(0xB));
            ++__first;
            break;
        case 'c':
            if ((__t = _VSTD::next(__first)) != __last)
            {
                if (('A' <= *__t && *__t <= 'Z') ||
                    ('a' <= *__t && *__t <= 'z'))
                {
                    if (__str)
                        *__str = _CharT(*__t % 32);
                    else
                        __push_char(_CharT(*__t % 32));
                    __first = ++__t;
                }
                else
                    __throw_regex_error<regex_constants::error_escape>();
            }
            else
                __throw_regex_error<regex_constants::error_escape>();
            break;
        case 'u':
            ++__first;
            if (__first == __last)
                __throw_regex_error<regex_constants::error_escape>();
            __hd = __traits_.value(*__first, 16);
            if (__hd == -1)
                __throw_regex_error<regex_constants::error_escape>();
            __sum = 16 * __sum + static_cast<unsigned>(__hd);
            ++__first;
            if (__first == __last)
                __throw_regex_error<regex_constants::error_escape>();
            __hd = __traits_.value(*__first, 16);
            if (__hd == -1)
                __throw_regex_error<regex_constants::error_escape>();
            __sum = 16 * __sum + static_cast<unsigned>(__hd);
            // fallthrough
        case 'x':
            ++__first;
            if (__first == __last)
                __throw_regex_error<regex_constants::error_escape>();
            __hd = __traits_.value(*__first, 16);
            if (__hd == -1)
                __throw_regex_error<regex_constants::error_escape>();
            __sum = 16 * __sum + static_cast<unsigned>(__hd);
            ++__first;
            if (__first == __last)
                __throw_regex_error<regex_constants::error_escape>();
            __hd = __traits_.value(*__first, 16);
            if (__hd == -1)
                __throw_regex_error<regex_constants::error_escape>();
            __sum = 16 * __sum + static_cast<unsigned>(__hd);
            if (__str)
                *__str = _CharT(__sum);
            else
                __push_char(_CharT(__sum));
            ++__first;
            break;
        case '0':
            if (__str)
                *__str = _CharT(0);
            else
                __push_char(_CharT(0));
            ++__first;
            break;
        default:
            if (*__first != '_' && !__traits_.isctype(*__first, ctype_base::alnum))
            {
                if (__str)
                    *__str = *__first;
                else
                    __push_char(*__first);
                ++__first;
            }
            else
                __throw_regex_error<regex_constants::error_escape>();
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_pattern_character(_ForwardIterator __first,
                                                        _ForwardIterator __last)
{
    if (__first != __last)
    {
        switch (*__first)
        {
        case '^':
        case '$':
        case '\\':
        case '.':
        case '*':
        case '+':
        case '?':
        case '(':
        case ')':
        case '[':
        case ']':
        case '{':
        case '}':
        case '|':
            break;
        default:
            __push_char(*__first);
            ++__first;
            break;
        }
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_grep(_ForwardIterator __first,
                                           _ForwardIterator __last)
{
    __owns_one_state<_CharT>* __sa = __end_;
    _ForwardIterator __t1 = _VSTD::find(__first, __last, _CharT('\n'));
    if (__t1 != __first)
        __parse_basic_reg_exp(__first, __t1);
    else
        __push_empty();
    __first = __t1;
    if (__first != __last)
        ++__first;
    while (__first != __last)
    {
        __t1 = _VSTD::find(__first, __last, _CharT('\n'));
        __owns_one_state<_CharT>* __sb = __end_;
        if (__t1 != __first)
            __parse_basic_reg_exp(__first, __t1);
        else
            __push_empty();
        __push_alternation(__sa, __sb);
        __first = __t1;
        if (__first != __last)
            ++__first;
    }
    return __first;
}

template <class _CharT, class _Traits>
template <class _ForwardIterator>
_ForwardIterator
basic_regex<_CharT, _Traits>::__parse_egrep(_ForwardIterator __first,
                                            _ForwardIterator __last)
{
    __owns_one_state<_CharT>* __sa = __end_;
    _ForwardIterator __t1 = _VSTD::find(__first, __last, _CharT('\n'));
    if (__t1 != __first)
        __parse_extended_reg_exp(__first, __t1);
    else
        __push_empty();
    __first = __t1;
    if (__first != __last)
        ++__first;
    while (__first != __last)
    {
        __t1 = _VSTD::find(__first, __last, _CharT('\n'));
        __owns_one_state<_CharT>* __sb = __end_;
        if (__t1 != __first)
            __parse_extended_reg_exp(__first, __t1);
        else
            __push_empty();
        __push_alternation(__sa, __sb);
        __first = __t1;
        if (__first != __last)
            ++__first;
    }
    return __first;
}

template <class _CharT, class _Traits>
bool
basic_regex<_CharT, _Traits>::__test_back_ref(_CharT __c)
{
    unsigned __val = __traits_.value(__c, 10);
    if (__val >= 1 && __val <= 9)
    {
        if (__val > mark_count())
            __throw_regex_error<regex_constants::error_backref>();
        __push_back_ref(__val);
        return true;
    }

    return false;
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_loop(size_t __min, size_t __max,
        __owns_one_state<_CharT>* __s, size_t __mexp_begin, size_t __mexp_end,
        bool __greedy)
{
    unique_ptr<__empty_state<_CharT> > __e1(new __empty_state<_CharT>(__end_->first()));
    __end_->first() = nullptr;
    unique_ptr<__loop<_CharT> > __e2(new __loop<_CharT>(__loop_count_,
                __s->first(), __e1.get(), __mexp_begin, __mexp_end, __greedy,
                __min, __max));
    __s->first() = nullptr;
    __e1.release();
    __end_->first() = new __repeat_one_loop<_CharT>(__e2.get());
    __end_ = __e2->second();
    __s->first() = __e2.release();
    ++__loop_count_;
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_char(value_type __c)
{
    if (flags() & icase)
        __end_->first() = new __match_char_icase<_CharT, _Traits>
                                              (__traits_, __c, __end_->first());
    else if (flags() & collate)
        __end_->first() = new __match_char_collate<_CharT, _Traits>
                                              (__traits_, __c, __end_->first());
    else
        __end_->first() = new __match_char<_CharT>(__c, __end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_begin_marked_subexpression()
{
    if (!(__flags_ & nosubs))
    {
        __end_->first() =
                new __begin_marked_subexpression<_CharT>(++__marked_count_,
                                                         __end_->first());
        __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
    }
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_end_marked_subexpression(unsigned __sub)
{
    if (!(__flags_ & nosubs))
    {
        __end_->first() =
                new __end_marked_subexpression<_CharT>(__sub, __end_->first());
        __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
    }
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_l_anchor()
{
    __end_->first() = new __l_anchor_multiline<_CharT>(__use_multiline(), __end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_r_anchor()
{
    __end_->first() = new __r_anchor_multiline<_CharT>(__use_multiline(), __end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_match_any()
{
    __end_->first() = new __match_any<_CharT>(__end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_match_any_but_newline()
{
    __end_->first() = new __match_any_but_newline<_CharT>(__end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_empty()
{
    __end_->first() = new __empty_state<_CharT>(__end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_word_boundary(bool __invert)
{
    __end_->first() = new __word_boundary<_CharT, _Traits>(__traits_, __invert,
                                                           __end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_back_ref(int __i)
{
    if (flags() & icase)
        __end_->first() = new __back_ref_icase<_CharT, _Traits>
                                              (__traits_, __i, __end_->first());
    else if (flags() & collate)
        __end_->first() = new __back_ref_collate<_CharT, _Traits>
                                              (__traits_, __i, __end_->first());
    else
        __end_->first() = new __back_ref<_CharT>(__i, __end_->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_alternation(__owns_one_state<_CharT>* __sa,
                                                 __owns_one_state<_CharT>* __ea)
{
    __sa->first() = new __alternate<_CharT>(
                         static_cast<__owns_one_state<_CharT>*>(__sa->first()),
                         static_cast<__owns_one_state<_CharT>*>(__ea->first()));
    __ea->first() = nullptr;
    __ea->first() = new __empty_state<_CharT>(__end_->first());
    __end_->first() = nullptr;
    __end_->first() = new __empty_non_own_state<_CharT>(__ea->first());
    __end_ = static_cast<__owns_one_state<_CharT>*>(__ea->first());
}

template <class _CharT, class _Traits>
__bracket_expression<_CharT, _Traits>*
basic_regex<_CharT, _Traits>::__start_matching_list(bool __negate)
{
    __bracket_expression<_CharT, _Traits>* __r =
        new __bracket_expression<_CharT, _Traits>(__traits_, __end_->first(),
                                                  __negate, __flags_ & icase,
                                                  __flags_ & collate);
    __end_->first() = __r;
    __end_ = __r;
    return __r;
}

template <class _CharT, class _Traits>
void
basic_regex<_CharT, _Traits>::__push_lookahead(const basic_regex& __exp,
                                               bool __invert,
                                               unsigned __mexp)
{
    __end_->first() = new __lookahead<_CharT, _Traits>(__exp, __invert,
                                                           __end_->first(), __mexp);
    __end_ = static_cast<__owns_one_state<_CharT>*>(__end_->first());
}

// sub_match

typedef sub_match<const char*>             csub_match;
typedef sub_match<string::const_iterator>  ssub_match;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef sub_match<const wchar_t*>          wcsub_match;
typedef sub_match<wstring::const_iterator> wssub_match;
#endif

template <class _BidirectionalIterator>
class
    _LIBCPP_TEMPLATE_VIS
    _LIBCPP_PREFERRED_NAME(csub_match)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wcsub_match))
    _LIBCPP_PREFERRED_NAME(ssub_match)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wssub_match))
    sub_match
    : public pair<_BidirectionalIterator, _BidirectionalIterator>
{
public:
    typedef _BidirectionalIterator                              iterator;
    typedef typename iterator_traits<iterator>::value_type      value_type;
    typedef typename iterator_traits<iterator>::difference_type difference_type;
    typedef basic_string<value_type>                            string_type;

    bool matched;

    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR sub_match() : matched() {}

    _LIBCPP_INLINE_VISIBILITY
    difference_type length() const
        {return matched ? _VSTD::distance(this->first, this->second) : 0;}
    _LIBCPP_INLINE_VISIBILITY
    string_type str() const
        {return matched ? string_type(this->first, this->second) : string_type();}
    _LIBCPP_INLINE_VISIBILITY
    operator string_type() const
        {return str();}

    _LIBCPP_INLINE_VISIBILITY
    int compare(const sub_match& __s) const
        {return str().compare(__s.str());}
    _LIBCPP_INLINE_VISIBILITY
    int compare(const string_type& __s) const
        {return str().compare(__s);}
    _LIBCPP_INLINE_VISIBILITY
    int compare(const value_type* __s) const
        {return str().compare(__s);}

    _LIBCPP_HIDE_FROM_ABI
    void swap(sub_match& __s)
#ifndef _LIBCPP_CXX03_LANG
    _NOEXCEPT(__is_nothrow_swappable<_BidirectionalIterator>::value)
#endif // _LIBCPP_CXX03_LANG
    {
        this->pair<_BidirectionalIterator, _BidirectionalIterator>::swap(__s);
        std::swap(matched, __s.matched);
    }
};

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const sub_match<_BiIter>& __x, const sub_match<_BiIter>& __y)
{
    return __x.compare(__y) == 0;
}

#if _LIBCPP_STD_VER >= 20
template<class _BiIter>
using __sub_match_cat = compare_three_way_result_t<basic_string<typename iterator_traits<_BiIter>::value_type>>;

template <class _BiIter>
_LIBCPP_HIDE_FROM_ABI auto operator<=>(const sub_match<_BiIter>& __x, const sub_match<_BiIter>& __y) {
    return static_cast<__sub_match_cat<_BiIter>>(__x.compare(__y) <=> 0);
}
#else // _LIBCPP_STD_VER >= 20
template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const sub_match<_BiIter>& __x, const sub_match<_BiIter>& __y)
{
    return !(__x == __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const sub_match<_BiIter>& __x, const sub_match<_BiIter>& __y)
{
    return __x.compare(__y) < 0;
}

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

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

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const sub_match<_BiIter>& __x, const sub_match<_BiIter>& __y)
{
    return __y < __x;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
           const sub_match<_BiIter>& __y)
{
    return __y.compare(typename sub_match<_BiIter>::string_type(__x.data(), __x.size())) == 0;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
           const sub_match<_BiIter>& __y)
{
    return !(__x == __y);
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
          const sub_match<_BiIter>& __y)
{
    return __y.compare(typename sub_match<_BiIter>::string_type(__x.data(), __x.size())) > 0;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
          const sub_match<_BiIter>& __y)
{
    return __y < __x;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool operator>=(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
                const sub_match<_BiIter>& __y)
{
    return !(__x < __y);
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __x,
           const sub_match<_BiIter>& __y)
{
    return !(__y < __x);
}
#endif // _LIBCPP_STD_VER >= 20

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const sub_match<_BiIter>& __x,
           const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return __x.compare(typename sub_match<_BiIter>::string_type(__y.data(), __y.size())) == 0;
}

#if _LIBCPP_STD_VER >= 20
template <class _BiIter, class _ST, class _SA>
_LIBCPP_HIDE_FROM_ABI auto operator<=>(
    const sub_match<_BiIter>& __x, const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y) {
    return static_cast<__sub_match_cat<_BiIter>>(
        __x.compare(typename sub_match<_BiIter>::string_type(__y.data(), __y.size())) <=> 0);
}
#else // _LIBCPP_STD_VER >= 20
template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const sub_match<_BiIter>& __x,
           const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return !(__x == __y);
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const sub_match<_BiIter>& __x,
          const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return __x.compare(typename sub_match<_BiIter>::string_type(__y.data(), __y.size())) < 0;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool operator>(const sub_match<_BiIter>& __x,
               const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return __y < __x;
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const sub_match<_BiIter>& __x,
           const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return !(__x < __y);
}

template <class _BiIter, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const sub_match<_BiIter>& __x,
           const basic_string<typename iterator_traits<_BiIter>::value_type, _ST, _SA>& __y)
{
    return !(__y < __x);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(typename iterator_traits<_BiIter>::value_type const* __x,
           const sub_match<_BiIter>& __y)
{
    return __y.compare(__x) == 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(typename iterator_traits<_BiIter>::value_type const* __x,
           const sub_match<_BiIter>& __y)
{
    return !(__x == __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(typename iterator_traits<_BiIter>::value_type const* __x,
          const sub_match<_BiIter>& __y)
{
    return __y.compare(__x) > 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(typename iterator_traits<_BiIter>::value_type const* __x,
          const sub_match<_BiIter>& __y)
{
    return __y < __x;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(typename iterator_traits<_BiIter>::value_type const* __x,
           const sub_match<_BiIter>& __y)
{
    return !(__x < __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(typename iterator_traits<_BiIter>::value_type const* __x,
           const sub_match<_BiIter>& __y)
{
    return !(__y < __x);
}
#endif // _LIBCPP_STD_VER >= 20

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const* __y)
{
    return __x.compare(__y) == 0;
}

#if _LIBCPP_STD_VER >= 20
template <class _BiIter>
_LIBCPP_HIDE_FROM_ABI auto
operator<=>(const sub_match<_BiIter>& __x, typename iterator_traits<_BiIter>::value_type const* __y) {
    return static_cast<__sub_match_cat<_BiIter>>(__x.compare(__y) <=> 0);
}
#else // _LIBCPP_STD_VER >= 20
template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const* __y)
{
    return !(__x == __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const sub_match<_BiIter>& __x,
          typename iterator_traits<_BiIter>::value_type const* __y)
{
    return __x.compare(__y) < 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const sub_match<_BiIter>& __x,
          typename iterator_traits<_BiIter>::value_type const* __y)
{
    return __y < __x;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const* __y)
{
    return !(__x < __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const* __y)
{
    return !(__y < __x);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(typename iterator_traits<_BiIter>::value_type const& __x,
           const sub_match<_BiIter>& __y)
{
    typedef basic_string<typename iterator_traits<_BiIter>::value_type> string_type;
    return __y.compare(string_type(1, __x)) == 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(typename iterator_traits<_BiIter>::value_type const& __x,
           const sub_match<_BiIter>& __y)
{
    return !(__x == __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(typename iterator_traits<_BiIter>::value_type const& __x,
          const sub_match<_BiIter>& __y)
{
    typedef basic_string<typename iterator_traits<_BiIter>::value_type> string_type;
    return __y.compare(string_type(1, __x)) > 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(typename iterator_traits<_BiIter>::value_type const& __x,
          const sub_match<_BiIter>& __y)
{
    return __y < __x;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(typename iterator_traits<_BiIter>::value_type const& __x,
           const sub_match<_BiIter>& __y)
{
    return !(__x < __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(typename iterator_traits<_BiIter>::value_type const& __x,
           const sub_match<_BiIter>& __y)
{
    return !(__y < __x);
}
#endif // _LIBCPP_STD_VER >= 20

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const& __y)
{
    typedef basic_string<typename iterator_traits<_BiIter>::value_type> string_type;
    return __x.compare(string_type(1, __y)) == 0;
}

#if _LIBCPP_STD_VER >= 20
template <class _BiIter>
_LIBCPP_HIDE_FROM_ABI auto
operator<=>(const sub_match<_BiIter>& __x, typename iterator_traits<_BiIter>::value_type const& __y) {
    using string_type = basic_string<typename iterator_traits<_BiIter>::value_type>;
    return static_cast<__sub_match_cat<_BiIter>>(__x.compare(string_type(1, __y)) <=> 0);
}
#else // _LIBCPP_STD_VER >= 20
template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const& __y)
{
    return !(__x == __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const sub_match<_BiIter>& __x,
          typename iterator_traits<_BiIter>::value_type const& __y)
{
    typedef basic_string<typename iterator_traits<_BiIter>::value_type> string_type;
    return __x.compare(string_type(1, __y)) < 0;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const sub_match<_BiIter>& __x,
          typename iterator_traits<_BiIter>::value_type const& __y)
{
    return __y < __x;
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const& __y)
{
    return !(__x < __y);
}

template <class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const sub_match<_BiIter>& __x,
           typename iterator_traits<_BiIter>::value_type const& __y)
{
    return !(__y < __x);
}
#endif // _LIBCPP_STD_VER >= 20

template <class _CharT, class _ST, class _BiIter>
inline _LIBCPP_INLINE_VISIBILITY
basic_ostream<_CharT, _ST>&
operator<<(basic_ostream<_CharT, _ST>& __os, const sub_match<_BiIter>& __m)
{
    return __os << __m.str();
}

typedef match_results<const char*>             cmatch;
typedef match_results<string::const_iterator>  smatch;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef match_results<const wchar_t*>          wcmatch;
typedef match_results<wstring::const_iterator> wsmatch;
#endif

template <class _BidirectionalIterator, class _Allocator>
class
    _LIBCPP_TEMPLATE_VIS
    _LIBCPP_PREFERRED_NAME(cmatch)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wcmatch))
    _LIBCPP_PREFERRED_NAME(smatch)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wsmatch))
    match_results
{
public:
    typedef _Allocator                                        allocator_type;
    typedef sub_match<_BidirectionalIterator>                 value_type;
private:
    typedef vector<value_type, allocator_type>                __container_type;

    __container_type  __matches_;
    value_type __unmatched_;
    value_type __prefix_;
    value_type __suffix_;
    bool       __ready_;
public:
    _BidirectionalIterator __position_start_;
    typedef const value_type&                                 const_reference;
    typedef value_type&                                       reference;
    typedef typename __container_type::const_iterator         const_iterator;
    typedef const_iterator                                    iterator;
    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
    typedef typename allocator_traits<allocator_type>::size_type size_type;
    typedef typename iterator_traits<_BidirectionalIterator>::value_type char_type;
    typedef basic_string<char_type>                           string_type;

    // construct/copy/destroy:
#ifndef _LIBCPP_CXX03_LANG
    match_results() : match_results(allocator_type()) {}
    explicit match_results(const allocator_type& __a);
#else
    explicit match_results(const allocator_type& __a = allocator_type());
#endif

//    match_results(const match_results&) = default;
//    match_results& operator=(const match_results&) = default;
//    match_results(match_results&& __m) = default;
//    match_results& operator=(match_results&& __m) = default;
//    ~match_results() = default;

    _LIBCPP_INLINE_VISIBILITY
    bool ready() const {return __ready_;}

    // size:
    _LIBCPP_INLINE_VISIBILITY
    size_type size() const _NOEXCEPT {return __matches_.size();}
    _LIBCPP_INLINE_VISIBILITY
    size_type max_size() const _NOEXCEPT {return __matches_.max_size();}
    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
    bool empty() const _NOEXCEPT {return size() == 0;}

    // element access:
    _LIBCPP_INLINE_VISIBILITY
    difference_type length(size_type __sub = 0) const
        {
        _LIBCPP_ASSERT(ready(), "match_results::length() called when not ready");
        return (*this)[__sub].length();
        }
    _LIBCPP_INLINE_VISIBILITY
    difference_type position(size_type __sub = 0) const
        {
        _LIBCPP_ASSERT(ready(), "match_results::position() called when not ready");
        return _VSTD::distance(__position_start_, (*this)[__sub].first);
        }
    _LIBCPP_INLINE_VISIBILITY
    string_type str(size_type __sub = 0) const
        {
        _LIBCPP_ASSERT(ready(), "match_results::str() called when not ready");
        return (*this)[__sub].str();
        }
    _LIBCPP_INLINE_VISIBILITY
    const_reference operator[](size_type __n) const
        {
        _LIBCPP_ASSERT(ready(), "match_results::operator[]() called when not ready");
        return __n < __matches_.size() ? __matches_[__n] : __unmatched_;
        }

    _LIBCPP_INLINE_VISIBILITY
    const_reference prefix() const
        {
        _LIBCPP_ASSERT(ready(), "match_results::prefix() called when not ready");
        return __prefix_;
        }
    _LIBCPP_INLINE_VISIBILITY
    const_reference suffix() const
        {
        _LIBCPP_ASSERT(ready(), "match_results::suffix() called when not ready");
        return __suffix_;
        }

    _LIBCPP_INLINE_VISIBILITY
    const_iterator begin() const {return empty() ? __matches_.end() : __matches_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator end() const {return __matches_.end();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator cbegin() const {return empty() ? __matches_.end() : __matches_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator cend() const {return __matches_.end();}

    // format:
    template <class _OutputIter>
        _OutputIter
        format(_OutputIter __output_iter, const char_type* __fmt_first,
               const char_type* __fmt_last,
               regex_constants::match_flag_type __flags = regex_constants::format_default) const;
    template <class _OutputIter, class _ST, class _SA>
        _LIBCPP_INLINE_VISIBILITY
        _OutputIter
        format(_OutputIter __output_iter, const basic_string<char_type, _ST, _SA>& __fmt,
               regex_constants::match_flag_type __flags = regex_constants::format_default) const
            {return format(__output_iter, __fmt.data(), __fmt.data() + __fmt.size(), __flags);}
    template <class _ST, class _SA>
        _LIBCPP_INLINE_VISIBILITY
        basic_string<char_type, _ST, _SA>
        format(const basic_string<char_type, _ST, _SA>& __fmt,
               regex_constants::match_flag_type __flags = regex_constants::format_default) const
        {
            basic_string<char_type, _ST, _SA> __r;
            format(std::back_inserter(__r), __fmt.data(), __fmt.data() + __fmt.size(),
                   __flags);
            return __r;
        }
    _LIBCPP_INLINE_VISIBILITY
    string_type
        format(const char_type* __fmt,
               regex_constants::match_flag_type __flags = regex_constants::format_default) const
        {
            string_type __r;
            format(std::back_inserter(__r), __fmt,
                   __fmt + char_traits<char_type>::length(__fmt), __flags);
            return __r;
        }

    // allocator:
    _LIBCPP_INLINE_VISIBILITY
    allocator_type get_allocator() const {return __matches_.get_allocator();}

    // swap:
    void swap(match_results& __m);

    template <class _Bp, class _Ap>
        _LIBCPP_INLINE_VISIBILITY
        void __assign(_BidirectionalIterator __f, _BidirectionalIterator __l,
                      const match_results<_Bp, _Ap>& __m, bool __no_update_pos)
    {
        _Bp __mf = __m.prefix().first;
        __matches_.resize(__m.size());
        for (size_type __i = 0; __i < __matches_.size(); ++__i)
        {
            __matches_[__i].first = _VSTD::next(__f, _VSTD::distance(__mf, __m[__i].first));
            __matches_[__i].second = _VSTD::next(__f, _VSTD::distance(__mf, __m[__i].second));
            __matches_[__i].matched = __m[__i].matched;
        }
        __unmatched_.first   = __l;
        __unmatched_.second  = __l;
        __unmatched_.matched = false;
        __prefix_.first = _VSTD::next(__f, _VSTD::distance(__mf, __m.prefix().first));
        __prefix_.second = _VSTD::next(__f, _VSTD::distance(__mf, __m.prefix().second));
        __prefix_.matched = __m.prefix().matched;
        __suffix_.first = _VSTD::next(__f, _VSTD::distance(__mf, __m.suffix().first));
        __suffix_.second = _VSTD::next(__f, _VSTD::distance(__mf, __m.suffix().second));
        __suffix_.matched = __m.suffix().matched;
        if (!__no_update_pos)
            __position_start_ = __prefix_.first;
        __ready_ = __m.ready();
    }

private:
    void __init(unsigned __s,
                _BidirectionalIterator __f, _BidirectionalIterator __l,
                bool __no_update_pos = false);

    template <class, class> friend class basic_regex;

    template <class _Bp, class _Ap, class _Cp, class _Tp>
    friend
    bool
    regex_match(_Bp, _Bp, match_results<_Bp, _Ap>&, const basic_regex<_Cp, _Tp>&,
                regex_constants::match_flag_type);

    template <class _Bp, class _Ap>
    friend
    bool
    operator==(const match_results<_Bp, _Ap>&, const match_results<_Bp, _Ap>&);

    template <class, class> friend class __lookahead;
};

template <class _BidirectionalIterator, class _Allocator>
match_results<_BidirectionalIterator, _Allocator>::match_results(
        const allocator_type& __a)
    : __matches_(__a),
      __unmatched_(),
      __prefix_(),
      __suffix_(),
      __ready_(false),
      __position_start_()
{
}

template <class _BidirectionalIterator, class _Allocator>
void
match_results<_BidirectionalIterator, _Allocator>::__init(unsigned __s,
                         _BidirectionalIterator __f, _BidirectionalIterator __l,
                         bool __no_update_pos)
{
    __unmatched_.first   = __l;
    __unmatched_.second  = __l;
    __unmatched_.matched = false;
    __matches_.assign(__s, __unmatched_);
    __prefix_.first      = __f;
    __prefix_.second     = __f;
    __prefix_.matched    = false;
    __suffix_ = __unmatched_;
    if (!__no_update_pos)
        __position_start_ = __prefix_.first;
    __ready_ = true;
}

template <class _BidirectionalIterator, class _Allocator>
template <class _OutputIter>
_OutputIter
match_results<_BidirectionalIterator, _Allocator>::format(_OutputIter __output_iter,
        const char_type* __fmt_first, const char_type* __fmt_last,
        regex_constants::match_flag_type __flags) const
{
    _LIBCPP_ASSERT(ready(), "match_results::format() called when not ready");
    if (__flags & regex_constants::format_sed)
    {
        for (; __fmt_first != __fmt_last; ++__fmt_first)
        {
            if (*__fmt_first == '&')
                __output_iter = _VSTD::copy(__matches_[0].first, __matches_[0].second,
                                   __output_iter);
            else if (*__fmt_first == '\\' && __fmt_first + 1 != __fmt_last)
            {
                ++__fmt_first;
                if ('0' <= *__fmt_first && *__fmt_first <= '9')
                {
                    size_t __i = *__fmt_first - '0';
                    __output_iter = _VSTD::copy((*this)[__i].first,
                                        (*this)[__i].second, __output_iter);
                }
                else
                {
                    *__output_iter = *__fmt_first;
                    ++__output_iter;
                }
            }
            else
            {
                *__output_iter = *__fmt_first;
                ++__output_iter;
            }
        }
    }
    else
    {
        for (; __fmt_first != __fmt_last; ++__fmt_first)
        {
            if (*__fmt_first == '$' && __fmt_first + 1 != __fmt_last)
            {
                switch (__fmt_first[1])
                {
                case '$':
                    *__output_iter = *++__fmt_first;
                    ++__output_iter;
                    break;
                case '&':
                    ++__fmt_first;
                    __output_iter = _VSTD::copy(__matches_[0].first, __matches_[0].second,
                                       __output_iter);
                    break;
                case '`':
                    ++__fmt_first;
                    __output_iter = _VSTD::copy(__prefix_.first, __prefix_.second, __output_iter);
                    break;
                case '\'':
                    ++__fmt_first;
                    __output_iter = _VSTD::copy(__suffix_.first, __suffix_.second, __output_iter);
                    break;
                default:
                    if ('0' <= __fmt_first[1] && __fmt_first[1] <= '9')
                    {
                        ++__fmt_first;
                        size_t __idx = *__fmt_first - '0';
                        if (__fmt_first + 1 != __fmt_last &&
                            '0' <= __fmt_first[1] && __fmt_first[1] <= '9')
                        {
                            ++__fmt_first;
                            if (__idx >= numeric_limits<size_t>::max() / 10)
                                __throw_regex_error<regex_constants::error_escape>();
                            __idx = 10 * __idx + *__fmt_first - '0';
                        }
                        __output_iter = _VSTD::copy((*this)[__idx].first,
                                            (*this)[__idx].second, __output_iter);
                    }
                    else
                    {
                        *__output_iter = *__fmt_first;
                        ++__output_iter;
                    }
                    break;
                }
            }
            else
            {
                *__output_iter = *__fmt_first;
                ++__output_iter;
            }
        }
    }
    return __output_iter;
}

template <class _BidirectionalIterator, class _Allocator>
void
match_results<_BidirectionalIterator, _Allocator>::swap(match_results& __m)
{
    using _VSTD::swap;
    swap(__matches_, __m.__matches_);
    swap(__unmatched_, __m.__unmatched_);
    swap(__prefix_, __m.__prefix_);
    swap(__suffix_, __m.__suffix_);
    swap(__position_start_, __m.__position_start_);
    swap(__ready_, __m.__ready_);
}

template <class _BidirectionalIterator, class _Allocator>
_LIBCPP_HIDE_FROM_ABI bool
operator==(const match_results<_BidirectionalIterator, _Allocator>& __x,
           const match_results<_BidirectionalIterator, _Allocator>& __y)
{
    if (__x.__ready_ != __y.__ready_)
        return false;
    if (!__x.__ready_)
        return true;
    return __x.__matches_ == __y.__matches_ &&
           __x.__prefix_ == __y.__prefix_ &&
           __x.__suffix_ == __y.__suffix_;
}

template <class _BidirectionalIterator, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const match_results<_BidirectionalIterator, _Allocator>& __x,
           const match_results<_BidirectionalIterator, _Allocator>& __y)
{
    return !(__x == __y);
}

template <class _BidirectionalIterator, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(match_results<_BidirectionalIterator, _Allocator>& __x,
     match_results<_BidirectionalIterator, _Allocator>& __y)
{
    __x.swap(__y);
}

// regex_search

template <class _CharT, class _Traits>
template <class _Allocator>
bool
basic_regex<_CharT, _Traits>::__match_at_start_ecma(
        const _CharT* __first, const _CharT* __last,
        match_results<const _CharT*, _Allocator>& __m,
        regex_constants::match_flag_type __flags, bool __at_first) const
{
    vector<__state> __states;
    __node* __st = __start_.get();
    if (__st)
    {
        sub_match<const _CharT*> __unmatched;
        __unmatched.first   = __last;
        __unmatched.second  = __last;
        __unmatched.matched = false;

        __states.push_back(__state());
        __states.back().__do_ = 0;
        __states.back().__first_ = __first;
        __states.back().__current_ = __first;
        __states.back().__last_ = __last;
        __states.back().__sub_matches_.resize(mark_count(), __unmatched);
        __states.back().__loop_data_.resize(__loop_count());
        __states.back().__node_ = __st;
        __states.back().__flags_ = __flags;
        __states.back().__at_first_ = __at_first;
        int __counter = 0;
        int __length = __last - __first;
        do
        {
            ++__counter;
            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
              __throw_regex_error<regex_constants::error_complexity>();
            __state& __s = __states.back();
            if (__s.__node_)
                __s.__node_->__exec(__s);
            switch (__s.__do_)
            {
            case __state::__end_state:
                if ((__flags & regex_constants::match_not_null) &&
                    __s.__current_ == __first)
                {
                  __states.pop_back();
                  break;
                }
                if ((__flags & regex_constants::__full_match) &&
                    __s.__current_ != __last)
                {
                  __states.pop_back();
                  break;
                }
                __m.__matches_[0].first = __first;
                __m.__matches_[0].second = _VSTD::next(__first, __s.__current_ - __first);
                __m.__matches_[0].matched = true;
                for (unsigned __i = 0; __i < __s.__sub_matches_.size(); ++__i)
                    __m.__matches_[__i+1] = __s.__sub_matches_[__i];
                return true;
            case __state::__accept_and_consume:
            case __state::__repeat:
            case __state::__accept_but_not_consume:
                break;
            case __state::__split:
                {
                __state __snext = __s;
                __s.__node_->__exec_split(true, __s);
                __snext.__node_->__exec_split(false, __snext);
                __states.push_back(_VSTD::move(__snext));
                }
                break;
            case __state::__reject:
                __states.pop_back();
                break;
            default:
                __throw_regex_error<regex_constants::__re_err_unknown>();
                break;

            }
        } while (!__states.empty());
    }
    return false;
}

template <class _CharT, class _Traits>
template <class _Allocator>
bool
basic_regex<_CharT, _Traits>::__match_at_start_posix_nosubs(
        const _CharT* __first, const _CharT* __last,
        match_results<const _CharT*, _Allocator>& __m,
        regex_constants::match_flag_type __flags, bool __at_first) const
{
    deque<__state> __states;
    ptrdiff_t __highest_j = 0;
    ptrdiff_t __np = _VSTD::distance(__first, __last);
    __node* __st = __start_.get();
    if (__st)
    {
        __states.push_back(__state());
        __states.back().__do_ = 0;
        __states.back().__first_ = __first;
        __states.back().__current_ = __first;
        __states.back().__last_ = __last;
        __states.back().__loop_data_.resize(__loop_count());
        __states.back().__node_ = __st;
        __states.back().__flags_ = __flags;
        __states.back().__at_first_ = __at_first;
        bool __matched = false;
        int __counter = 0;
        int __length = __last - __first;
        do
        {
            ++__counter;
            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
              __throw_regex_error<regex_constants::error_complexity>();
            __state& __s = __states.back();
            if (__s.__node_)
                __s.__node_->__exec(__s);
            switch (__s.__do_)
            {
            case __state::__end_state:
                if ((__flags & regex_constants::match_not_null) &&
                    __s.__current_ == __first)
                {
                  __states.pop_back();
                  break;
                }
                if ((__flags & regex_constants::__full_match) &&
                    __s.__current_ != __last)
                {
                  __states.pop_back();
                  break;
                }
                if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                    __highest_j = __s.__current_ - __s.__first_;
                __matched = true;
                if (__highest_j == __np)
                    __states.clear();
                else
                    __states.pop_back();
                break;
            case __state::__consume_input:
                break;
            case __state::__accept_and_consume:
                __states.push_front(_VSTD::move(__s));
                __states.pop_back();
                break;
            case __state::__repeat:
            case __state::__accept_but_not_consume:
                break;
            case __state::__split:
                {
                __state __snext = __s;
                __s.__node_->__exec_split(true, __s);
                __snext.__node_->__exec_split(false, __snext);
                __states.push_back(_VSTD::move(__snext));
                }
                break;
            case __state::__reject:
                __states.pop_back();
                break;
            default:
                __throw_regex_error<regex_constants::__re_err_unknown>();
                break;
            }
        } while (!__states.empty());
        if (__matched)
        {
            __m.__matches_[0].first = __first;
            __m.__matches_[0].second = _VSTD::next(__first, __highest_j);
            __m.__matches_[0].matched = true;
            return true;
        }
    }
    return false;
}

template <class _CharT, class _Traits>
template <class _Allocator>
bool
basic_regex<_CharT, _Traits>::__match_at_start_posix_subs(
        const _CharT* __first, const _CharT* __last,
        match_results<const _CharT*, _Allocator>& __m,
        regex_constants::match_flag_type __flags, bool __at_first) const
{
    vector<__state> __states;
    __state __best_state;
    ptrdiff_t __highest_j = 0;
    ptrdiff_t __np = _VSTD::distance(__first, __last);
    __node* __st = __start_.get();
    if (__st)
    {
        sub_match<const _CharT*> __unmatched;
        __unmatched.first   = __last;
        __unmatched.second  = __last;
        __unmatched.matched = false;

        __states.push_back(__state());
        __states.back().__do_ = 0;
        __states.back().__first_ = __first;
        __states.back().__current_ = __first;
        __states.back().__last_ = __last;
        __states.back().__sub_matches_.resize(mark_count(), __unmatched);
        __states.back().__loop_data_.resize(__loop_count());
        __states.back().__node_ = __st;
        __states.back().__flags_ = __flags;
        __states.back().__at_first_ = __at_first;
        bool __matched = false;
        int __counter = 0;
        int __length = __last - __first;
        do
        {
            ++__counter;
            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
              __throw_regex_error<regex_constants::error_complexity>();
            __state& __s = __states.back();
            if (__s.__node_)
                __s.__node_->__exec(__s);
            switch (__s.__do_)
            {
            case __state::__end_state:
                if ((__flags & regex_constants::match_not_null) &&
                    __s.__current_ == __first)
                {
                  __states.pop_back();
                  break;
                }
                if ((__flags & regex_constants::__full_match) &&
                    __s.__current_ != __last)
                {
                  __states.pop_back();
                  break;
                }
                if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                {
                    __highest_j = __s.__current_ - __s.__first_;
                    __best_state = __s;
                }
                __matched = true;
                if (__highest_j == __np)
                    __states.clear();
                else
                    __states.pop_back();
                break;
            case __state::__accept_and_consume:
            case __state::__repeat:
            case __state::__accept_but_not_consume:
                break;
            case __state::__split:
                {
                __state __snext = __s;
                __s.__node_->__exec_split(true, __s);
                __snext.__node_->__exec_split(false, __snext);
                __states.push_back(_VSTD::move(__snext));
                }
                break;
            case __state::__reject:
                __states.pop_back();
                break;
            default:
                __throw_regex_error<regex_constants::__re_err_unknown>();
                break;
            }
        } while (!__states.empty());
        if (__matched)
        {
            __m.__matches_[0].first = __first;
            __m.__matches_[0].second = _VSTD::next(__first, __highest_j);
            __m.__matches_[0].matched = true;
            for (unsigned __i = 0; __i < __best_state.__sub_matches_.size(); ++__i)
                __m.__matches_[__i+1] = __best_state.__sub_matches_[__i];
            return true;
        }
    }
    return false;
}

template <class _CharT, class _Traits>
template <class _Allocator>
bool
basic_regex<_CharT, _Traits>::__match_at_start(
        const _CharT* __first, const _CharT* __last,
        match_results<const _CharT*, _Allocator>& __m,
        regex_constants::match_flag_type __flags, bool __at_first) const
{
    if (__get_grammar(__flags_) == ECMAScript)
        return __match_at_start_ecma(__first, __last, __m, __flags, __at_first);
    if (mark_count() == 0)
        return __match_at_start_posix_nosubs(__first, __last, __m, __flags, __at_first);
    return __match_at_start_posix_subs(__first, __last, __m, __flags, __at_first);
}

template <class _CharT, class _Traits>
template <class _Allocator>
bool
basic_regex<_CharT, _Traits>::__search(
        const _CharT* __first, const _CharT* __last,
        match_results<const _CharT*, _Allocator>& __m,
        regex_constants::match_flag_type __flags) const
{
    if (__flags & regex_constants::match_prev_avail)
        __flags &= ~(regex_constants::match_not_bol | regex_constants::match_not_bow);

    __m.__init(1 + mark_count(), __first, __last,
                                    __flags & regex_constants::__no_update_pos);
    if (__match_at_start(__first, __last, __m, __flags,
                                    !(__flags & regex_constants::__no_update_pos)))
    {
        __m.__prefix_.second = __m[0].first;
        __m.__prefix_.matched = __m.__prefix_.first != __m.__prefix_.second;
        __m.__suffix_.first = __m[0].second;
        __m.__suffix_.matched = __m.__suffix_.first != __m.__suffix_.second;
        return true;
    }
    if (__first != __last && !(__flags & regex_constants::match_continuous))
    {
        __flags |= regex_constants::match_prev_avail;
        for (++__first; __first != __last; ++__first)
        {
            __m.__matches_.assign(__m.size(), __m.__unmatched_);
            if (__match_at_start(__first, __last, __m, __flags, false))
            {
                __m.__prefix_.second = __m[0].first;
                __m.__prefix_.matched = __m.__prefix_.first != __m.__prefix_.second;
                __m.__suffix_.first = __m[0].second;
                __m.__suffix_.matched = __m.__suffix_.first != __m.__suffix_.second;
                return true;
            }
            __m.__matches_.assign(__m.size(), __m.__unmatched_);
        }
    }
    __m.__matches_.clear();
    return false;
}

template <class _BidirectionalIterator, class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(_BidirectionalIterator __first, _BidirectionalIterator __last,
             match_results<_BidirectionalIterator, _Allocator>& __m,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    int __offset = (__flags & regex_constants::match_prev_avail) ? 1 : 0;
    basic_string<_CharT> __s(_VSTD::prev(__first, __offset), __last);
    match_results<const _CharT*> __mc;
    bool __r = __e.__search(__s.data() + __offset, __s.data() + __s.size(), __mc, __flags);
    __m.__assign(__first, __last, __mc, __flags & regex_constants::__no_update_pos);
    return __r;
}

template <class _Iter, class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(__wrap_iter<_Iter> __first,
             __wrap_iter<_Iter> __last,
             match_results<__wrap_iter<_Iter>, _Allocator>& __m,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<const _CharT*> __mc;
    bool __r = __e.__search(__first.base(), __last.base(), __mc, __flags);
    __m.__assign(__first, __last, __mc, __flags & regex_constants::__no_update_pos);
    return __r;
}

template <class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const _CharT* __first, const _CharT* __last,
             match_results<const _CharT*, _Allocator>& __m,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return __e.__search(__first, __last, __m, __flags);
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(_BidirectionalIterator __first, _BidirectionalIterator __last,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    basic_string<_CharT> __s(__first, __last);
    match_results<const _CharT*> __mc;
    return __e.__search(__s.data(), __s.data() + __s.size(), __mc, __flags);
}

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const _CharT* __first, const _CharT* __last,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<const _CharT*> __mc;
    return __e.__search(__first, __last, __mc, __flags);
}

template <class _CharT, class _Allocator, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const _CharT* __str, match_results<const _CharT*, _Allocator>& __m,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return __e.__search(__str, __str + _Traits::length(__str), __m, __flags);
}

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const _CharT* __str, const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<const _CharT*> __m;
    return _VSTD::regex_search(__str, __m, __e, __flags);
}

template <class _ST, class _SA, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const basic_string<_CharT, _ST, _SA>& __s,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<const _CharT*> __mc;
    return __e.__search(__s.data(), __s.data() + __s.size(), __mc, __flags);
}

template <class _ST, class _SA, class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_search(const basic_string<_CharT, _ST, _SA>& __s,
             match_results<typename basic_string<_CharT, _ST, _SA>::const_iterator, _Allocator>& __m,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<const _CharT*> __mc;
    bool __r = __e.__search(__s.data(), __s.data() + __s.size(), __mc, __flags);
    __m.__assign(__s.begin(), __s.end(), __mc, __flags & regex_constants::__no_update_pos);
    return __r;
}

#if _LIBCPP_STD_VER >= 14
template <class _ST, class _SA, class _Ap, class _Cp, class _Tp>
bool
regex_search(const basic_string<_Cp, _ST, _SA>&& __s,
             match_results<typename basic_string<_Cp, _ST, _SA>::const_iterator, _Ap>&,
             const basic_regex<_Cp, _Tp>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default) = delete;
#endif

// regex_match

template <class _BidirectionalIterator, class _Allocator, class _CharT, class _Traits>
_LIBCPP_HIDE_FROM_ABI bool
regex_match(_BidirectionalIterator __first, _BidirectionalIterator __last,
            match_results<_BidirectionalIterator, _Allocator>& __m,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    bool __r = _VSTD::regex_search(
        __first, __last, __m, __e,
        __flags | regex_constants::match_continuous |
        regex_constants::__full_match);
    if (__r)
    {
        __r = !__m.suffix().matched;
        if (!__r)
            __m.__matches_.clear();
    }
    return __r;
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(_BidirectionalIterator __first, _BidirectionalIterator __last,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    match_results<_BidirectionalIterator> __m;
    return _VSTD::regex_match(__first, __last, __m, __e, __flags);
}

template <class _CharT, class _Allocator, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(const _CharT* __str, match_results<const _CharT*, _Allocator>& __m,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return _VSTD::regex_match(__str, __str + _Traits::length(__str), __m, __e, __flags);
}

template <class _ST, class _SA, class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(const basic_string<_CharT, _ST, _SA>& __s,
            match_results<typename basic_string<_CharT, _ST, _SA>::const_iterator, _Allocator>& __m,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return _VSTD::regex_match(__s.begin(), __s.end(), __m, __e, __flags);
}

#if _LIBCPP_STD_VER >= 14
template <class _ST, class _SA, class _Allocator, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(const basic_string<_CharT, _ST, _SA>&& __s,
            match_results<typename basic_string<_CharT, _ST, _SA>::const_iterator, _Allocator>& __m,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default) = delete;
#endif

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(const _CharT* __str, const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return _VSTD::regex_match(__str, __str + _Traits::length(__str), __e, __flags);
}

template <class _ST, class _SA, class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool
regex_match(const basic_string<_CharT, _ST, _SA>& __s,
            const basic_regex<_CharT, _Traits>& __e,
            regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return _VSTD::regex_match(__s.begin(), __s.end(), __e, __flags);
}

// regex_iterator

template <class _BidirectionalIterator,
          class _CharT = typename iterator_traits<_BidirectionalIterator>::value_type,
          class _Traits = regex_traits<_CharT> >
    class _LIBCPP_TEMPLATE_VIS regex_iterator;

typedef regex_iterator<const char*>             cregex_iterator;
typedef regex_iterator<string::const_iterator>  sregex_iterator;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef regex_iterator<const wchar_t*>          wcregex_iterator;
typedef regex_iterator<wstring::const_iterator> wsregex_iterator;
#endif

template <class _BidirectionalIterator, class _CharT, class _Traits>
class
    _LIBCPP_TEMPLATE_VIS
    _LIBCPP_PREFERRED_NAME(cregex_iterator)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wcregex_iterator))
    _LIBCPP_PREFERRED_NAME(sregex_iterator)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wsregex_iterator))
    regex_iterator
{
public:
    typedef basic_regex<_CharT, _Traits>          regex_type;
    typedef match_results<_BidirectionalIterator> value_type;
    typedef ptrdiff_t                             difference_type;
    typedef const value_type*                     pointer;
    typedef const value_type&                     reference;
    typedef forward_iterator_tag                  iterator_category;

private:
    _BidirectionalIterator           __begin_;
    _BidirectionalIterator           __end_;
    const regex_type*                __pregex_;
    regex_constants::match_flag_type __flags_;
    value_type                       __match_;

public:
    regex_iterator();
    regex_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                   const regex_type& __re,
                   regex_constants::match_flag_type __m
                                              = regex_constants::match_default);
#if _LIBCPP_STD_VER >= 14
    regex_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                   const regex_type&& __re,
                   regex_constants::match_flag_type __m
                                     = regex_constants::match_default) = delete;
#endif

    bool operator==(const regex_iterator& __x) const;
    _LIBCPP_INLINE_VISIBILITY
    bool operator!=(const regex_iterator& __x) const {return !(*this == __x);}

    _LIBCPP_INLINE_VISIBILITY
    reference operator*() const {return  __match_;}
    _LIBCPP_INLINE_VISIBILITY
    pointer operator->() const  {return _VSTD::addressof(__match_);}

    regex_iterator& operator++();
    _LIBCPP_INLINE_VISIBILITY
    regex_iterator operator++(int)
    {
        regex_iterator __t(*this);
        ++(*this);
        return __t;
    }
};

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_iterator<_BidirectionalIterator, _CharT, _Traits>::regex_iterator()
    : __begin_(), __end_(), __pregex_(nullptr), __flags_(), __match_()
{
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                   const regex_type& __re, regex_constants::match_flag_type __m)
    : __begin_(__a),
      __end_(__b),
      __pregex_(_VSTD::addressof(__re)),
      __flags_(__m)
{
    _VSTD::regex_search(__begin_, __end_, __match_, *__pregex_, __flags_);
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
bool
regex_iterator<_BidirectionalIterator, _CharT, _Traits>::
    operator==(const regex_iterator& __x) const
{
    if (__match_.empty() && __x.__match_.empty())
        return true;
    if (__match_.empty() || __x.__match_.empty())
        return false;
    return __begin_ == __x.__begin_       &&
           __end_ == __x.__end_           &&
           __pregex_ == __x.__pregex_     &&
           __flags_ == __x.__flags_       &&
           __match_[0] == __x.__match_[0];
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_iterator<_BidirectionalIterator, _CharT, _Traits>&
regex_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++()
{
    __flags_ |= regex_constants::__no_update_pos;
    _BidirectionalIterator __start = __match_[0].second;
    if (__match_[0].first == __match_[0].second)
    {
        if (__start == __end_)
        {
            __match_ = value_type();
            return *this;
        }
        else if (_VSTD::regex_search(__start, __end_, __match_, *__pregex_,
                                    __flags_ | regex_constants::match_not_null |
                                    regex_constants::match_continuous))
            return *this;
        else
            ++__start;
    }
    __flags_ |= regex_constants::match_prev_avail;
    if (!_VSTD::regex_search(__start, __end_, __match_, *__pregex_, __flags_))
        __match_ = value_type();
    return *this;
}

// regex_token_iterator

template <class _BidirectionalIterator,
          class _CharT = typename iterator_traits<_BidirectionalIterator>::value_type,
          class _Traits = regex_traits<_CharT> >
    class _LIBCPP_TEMPLATE_VIS regex_token_iterator;

typedef regex_token_iterator<const char*>             cregex_token_iterator;
typedef regex_token_iterator<string::const_iterator>  sregex_token_iterator;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef regex_token_iterator<const wchar_t*>          wcregex_token_iterator;
typedef regex_token_iterator<wstring::const_iterator> wsregex_token_iterator;
#endif

template <class _BidirectionalIterator, class _CharT, class _Traits>
class
    _LIBCPP_TEMPLATE_VIS
    _LIBCPP_PREFERRED_NAME(cregex_token_iterator)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wcregex_token_iterator))
    _LIBCPP_PREFERRED_NAME(sregex_token_iterator)
    _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wsregex_token_iterator))
    regex_token_iterator
{
public:
    typedef basic_regex<_CharT, _Traits>      regex_type;
    typedef sub_match<_BidirectionalIterator> value_type;
    typedef ptrdiff_t                         difference_type;
    typedef const value_type*                 pointer;
    typedef const value_type&                 reference;
    typedef forward_iterator_tag              iterator_category;

private:
    typedef regex_iterator<_BidirectionalIterator, _CharT, _Traits> _Position;

    _Position         __position_;
    const value_type* __result_;
    value_type        __suffix_;
    ptrdiff_t         __n_;
    vector<int>       __subs_;

public:
    regex_token_iterator();
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re, int __submatch = 0,
                         regex_constants::match_flag_type __m =
                                                regex_constants::match_default);
#if _LIBCPP_STD_VER >= 14
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type&& __re, int __submatch = 0,
                         regex_constants::match_flag_type __m =
                                       regex_constants::match_default) = delete;
#endif

    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re, const vector<int>& __submatches,
                         regex_constants::match_flag_type __m =
                                                regex_constants::match_default);
#if _LIBCPP_STD_VER >= 14
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type&& __re, const vector<int>& __submatches,
                         regex_constants::match_flag_type __m =
                                     regex_constants::match_default) = delete;
#endif

#ifndef _LIBCPP_CXX03_LANG
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re,
                         initializer_list<int> __submatches,
                         regex_constants::match_flag_type __m =
                                                regex_constants::match_default);

#if _LIBCPP_STD_VER >= 14
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type&& __re,
                         initializer_list<int> __submatches,
                         regex_constants::match_flag_type __m =
                                       regex_constants::match_default) = delete;
#endif
#endif // _LIBCPP_CXX03_LANG
    template <size_t _Np>
        regex_token_iterator(_BidirectionalIterator __a,
                             _BidirectionalIterator __b,
                             const regex_type& __re,
                             const int (&__submatches)[_Np],
                             regex_constants::match_flag_type __m =
                                                regex_constants::match_default);
#if _LIBCPP_STD_VER >= 14
    template <size_t _Np>
        regex_token_iterator(_BidirectionalIterator __a,
                             _BidirectionalIterator __b,
                             const regex_type&& __re,
                             const int (&__submatches)[_Np],
                             regex_constants::match_flag_type __m =
                                      regex_constants::match_default) = delete;
#endif

    regex_token_iterator(const regex_token_iterator&);
    regex_token_iterator& operator=(const regex_token_iterator&);

    bool operator==(const regex_token_iterator& __x) const;
    _LIBCPP_INLINE_VISIBILITY
    bool operator!=(const regex_token_iterator& __x) const {return !(*this == __x);}

    _LIBCPP_INLINE_VISIBILITY
    const value_type& operator*() const {return *__result_;}
    _LIBCPP_INLINE_VISIBILITY
    const value_type* operator->() const {return __result_;}

    regex_token_iterator& operator++();
    _LIBCPP_INLINE_VISIBILITY
    regex_token_iterator operator++(int)
    {
        regex_token_iterator __t(*this);
        ++(*this);
        return __t;
    }

private:
    void __init(_BidirectionalIterator __a, _BidirectionalIterator __b);
    void __establish_result () {
        if (__subs_[__n_] == -1)
            __result_ = &__position_->prefix();
        else
            __result_ = &(*__position_)[__subs_[__n_]];
        }
};

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator()
    : __result_(nullptr),
      __suffix_(),
      __n_(0)
{
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
void
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    __init(_BidirectionalIterator __a, _BidirectionalIterator __b)
{
    if (__position_ != _Position())
        __establish_result ();
    else if (__subs_[__n_] == -1)
    {
        __suffix_.matched = true;
        __suffix_.first = __a;
        __suffix_.second = __b;
        __result_ = &__suffix_;
    }
    else
        __result_ = nullptr;
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re, int __submatch,
                         regex_constants::match_flag_type __m)
    : __position_(__a, __b, __re, __m),
      __n_(0),
      __subs_(1, __submatch)
{
    __init(__a, __b);
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re, const vector<int>& __submatches,
                         regex_constants::match_flag_type __m)
    : __position_(__a, __b, __re, __m),
      __n_(0),
      __subs_(__submatches)
{
    __init(__a, __b);
}

#ifndef _LIBCPP_CXX03_LANG

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                         const regex_type& __re,
                         initializer_list<int> __submatches,
                         regex_constants::match_flag_type __m)
    : __position_(__a, __b, __re, __m),
      __n_(0),
      __subs_(__submatches)
{
    __init(__a, __b);
}

#endif // _LIBCPP_CXX03_LANG

template <class _BidirectionalIterator, class _CharT, class _Traits>
template <size_t _Np>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                             const regex_type& __re,
                             const int (&__submatches)[_Np],
                             regex_constants::match_flag_type __m)
    : __position_(__a, __b, __re, __m),
      __n_(0),
      __subs_(begin(__submatches), end(__submatches))
{
    __init(__a, __b);
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    regex_token_iterator(const regex_token_iterator& __x)
    : __position_(__x.__position_),
      __result_(__x.__result_),
      __suffix_(__x.__suffix_),
      __n_(__x.__n_),
      __subs_(__x.__subs_)
{
    if (__x.__result_ == &__x.__suffix_)
        __result_ = &__suffix_;
    else if ( __result_ != nullptr )
        __establish_result ();
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>&
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    operator=(const regex_token_iterator& __x)
{
    if (this != &__x)
    {
        __position_ = __x.__position_;
        if (__x.__result_ == &__x.__suffix_)
            __result_ = &__suffix_;
        else
            __result_ = __x.__result_;
        __suffix_ = __x.__suffix_;
        __n_ = __x.__n_;
        __subs_ = __x.__subs_;

        if ( __result_ != nullptr && __result_ != &__suffix_ )
            __establish_result();
    }
    return *this;
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
bool
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
    operator==(const regex_token_iterator& __x) const
{
    if (__result_ == nullptr && __x.__result_ == nullptr)
        return true;
    if (__result_ == &__suffix_ && __x.__result_ == &__x.__suffix_ &&
            __suffix_ == __x.__suffix_)
        return true;
    if (__result_ == nullptr || __x.__result_ == nullptr)
        return false;
    if (__result_ == &__suffix_ || __x.__result_ == &__x.__suffix_)
        return false;
    return __position_ == __x.__position_ && __n_ == __x.__n_ &&
           __subs_ == __x.__subs_;
}

template <class _BidirectionalIterator, class _CharT, class _Traits>
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>&
regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++()
{
    _Position __prev = __position_;
    if (__result_ == &__suffix_)
        __result_ = nullptr;
    else if (static_cast<size_t>(__n_ + 1) < __subs_.size())
    {
        ++__n_;
        __establish_result();
    }
    else
    {
        __n_ = 0;
        ++__position_;
        if (__position_ != _Position())
            __establish_result();
        else
        {
            if (_VSTD::find(__subs_.begin(), __subs_.end(), -1) != __subs_.end()
                && __prev->suffix().length() != 0)
            {
                __suffix_.matched = true;
                __suffix_.first = __prev->suffix().first;
                __suffix_.second = __prev->suffix().second;
                __result_ = &__suffix_;
            }
            else
                __result_ = nullptr;
        }
    }
    return *this;
}

// regex_replace

template <class _OutputIterator, class _BidirectionalIterator,
          class _Traits, class _CharT>
_LIBCPP_HIDE_FROM_ABI _OutputIterator
regex_replace(_OutputIterator __output_iter,
              _BidirectionalIterator __first, _BidirectionalIterator __last,
              const basic_regex<_CharT, _Traits>& __e, const _CharT* __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    typedef regex_iterator<_BidirectionalIterator, _CharT, _Traits> _Iter;
    _Iter __i(__first, __last, __e, __flags);
    _Iter __eof;
    if (__i == __eof)
    {
        if (!(__flags & regex_constants::format_no_copy))
            __output_iter = _VSTD::copy(__first, __last, __output_iter);
    }
    else
    {
        sub_match<_BidirectionalIterator> __lm;
        for (size_t __len = char_traits<_CharT>::length(__fmt); __i != __eof; ++__i)
        {
            if (!(__flags & regex_constants::format_no_copy))
                __output_iter = _VSTD::copy(__i->prefix().first, __i->prefix().second, __output_iter);
            __output_iter = __i->format(__output_iter, __fmt, __fmt + __len, __flags);
            __lm = __i->suffix();
            if (__flags & regex_constants::format_first_only)
                break;
        }
        if (!(__flags & regex_constants::format_no_copy))
            __output_iter = _VSTD::copy(__lm.first, __lm.second, __output_iter);
    }
    return __output_iter;
}

template <class _OutputIterator, class _BidirectionalIterator,
          class _Traits, class _CharT, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
_OutputIterator
regex_replace(_OutputIterator __output_iter,
              _BidirectionalIterator __first, _BidirectionalIterator __last,
              const basic_regex<_CharT, _Traits>& __e,
              const basic_string<_CharT, _ST, _SA>& __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    return _VSTD::regex_replace(__output_iter, __first, __last, __e, __fmt.c_str(), __flags);
}

template <class _Traits, class _CharT, class _ST, class _SA, class _FST,
          class _FSA>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _ST, _SA>
regex_replace(const basic_string<_CharT, _ST, _SA>& __s,
              const basic_regex<_CharT, _Traits>& __e,
              const basic_string<_CharT, _FST, _FSA>& __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    basic_string<_CharT, _ST, _SA> __r;
    _VSTD::regex_replace(std::back_inserter(__r), __s.begin(), __s.end(), __e,
                        __fmt.c_str(), __flags);
    return __r;
}

template <class _Traits, class _CharT, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT, _ST, _SA>
regex_replace(const basic_string<_CharT, _ST, _SA>& __s,
              const basic_regex<_CharT, _Traits>& __e, const _CharT* __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    basic_string<_CharT, _ST, _SA> __r;
    _VSTD::regex_replace(std::back_inserter(__r), __s.begin(), __s.end(), __e,
                        __fmt, __flags);
    return __r;
}

template <class _Traits, class _CharT, class _ST, class _SA>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT>
regex_replace(const _CharT* __s,
              const basic_regex<_CharT, _Traits>& __e,
              const basic_string<_CharT, _ST, _SA>& __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    basic_string<_CharT> __r;
    _VSTD::regex_replace(std::back_inserter(__r), __s,
                        __s + char_traits<_CharT>::length(__s), __e,
                        __fmt.c_str(), __flags);
    return __r;
}

template <class _Traits, class _CharT>
inline _LIBCPP_INLINE_VISIBILITY
basic_string<_CharT>
regex_replace(const _CharT* __s,
              const basic_regex<_CharT, _Traits>& __e,
              const _CharT* __fmt,
              regex_constants::match_flag_type __flags = regex_constants::match_default)
{
    basic_string<_CharT> __r;
    _VSTD::regex_replace(std::back_inserter(__r), __s,
                        __s + char_traits<_CharT>::length(__s), __e,
                        __fmt, __flags);
    return __r;
}

_LIBCPP_END_NAMESPACE_STD

#if _LIBCPP_STD_VER >= 17
_LIBCPP_BEGIN_NAMESPACE_STD
namespace pmr {
template <class _BidirT>
using match_results = std::match_results<_BidirT, polymorphic_allocator<std::sub_match<_BidirT>>>;

using cmatch  = match_results<const char*>;
using smatch  = match_results<std::pmr::string::const_iterator>;

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
using wcmatch = match_results<const wchar_t*>;
using wsmatch = match_results<std::pmr::wstring::const_iterator>;
#endif
} // namespace pmr
_LIBCPP_END_NAMESPACE_STD
#endif

_LIBCPP_POP_MACROS

#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
#  include <atomic>
#  include <concepts>
#  include <cstdlib>
#  include <iosfwd>
#  include <iterator>
#  include <new>
#  include <type_traits>
#  include <typeinfo>
#  include <utility>
#endif

#endif // _LIBCPP_REGEX
