// -*- 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 <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;
};

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

template <class BiIter>
    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 <__config>
#include <__debug>
#include <__iterator/wrap_iter.h>
#include <__locale>
#include <compare>
#include <deque>
#include <initializer_list>
#include <iterator>
#include <memory>
#include <stdexcept>
#include <string>
#include <utility>
#include <vector>
#include <version>

#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
};

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);
    regex_error(const regex_error&) _NOEXCEPT = default;
    virtual ~regex_error() _NOEXCEPT;
     _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_NO_EXCEPTIONS
    throw regex_error(_Ev);
#else
    _VSTD::abort();
#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;
#ifdef __BIONIC__
    // 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.
    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_ = &use_facet<ctype<char_type> >(__loc_);
    __col_ = &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 = __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 __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_INLINE_VISIBILITY
    virtual ~__node() {}

    _LIBCPP_INLINE_VISIBILITY
    virtual void __exec(__state&) const {}
    _LIBCPP_INLINE_VISIBILITY
    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() {}

    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) {}

    virtual ~__owns_one_state();
};

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) {}

    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) {}

    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) {}

    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) {}

    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) {}

    virtual void __exec(__state& __s) const;
    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) {}

    virtual void __exec(__state& __s) const;
    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) {}

    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) {}

    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) {}

    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) {}

    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) {}

    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) {}

    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) {}

    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_ &&
             __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) {}

    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 && __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) {}

    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) {}

    virtual void __exec(__state&) const;
};

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) {}

    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)) {}

    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)) {}

    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") {}

    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(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(make_pair(_VSTD::move(__b), _VSTD::move(__e)));
            }
        }
    _LIBCPP_INLINE_VISIBILITY
    void __add_digraph(_CharT __c1, _CharT __c2)
        {
            if (__icase_)
                __digraphs_.push_back(make_pair(__traits_.translate_nocase(__c1),
                                                __traits_.translate_nocase(__c2)));
            else if (__collate_)
                __digraphs_.push_back(make_pair(__traits_.translate(__c1),
                                                __traits_.translate(__c2)));
            else
                __digraphs_.push_back(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_cpp17_input_iterator  <_InputIterator>::value &&
            !__is_cpp17_forward_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 c);

    _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) {}

    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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               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