include/iterator

// -*- C++ -*-
//===-------------------------- iterator ----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_ITERATOR
#define _LIBCPP_ITERATOR

/*
 iterator synopsis

namespace std
{

template<class Iterator>
struct iterator_traits
{
 typedef typename Iterator::difference_type difference_type;
 typedef typename Iterator::value_type value_type;
 typedef typename Iterator::pointer pointer;
 typedef typename Iterator::reference reference;
 typedef typename Iterator::iterator_category iterator_category;
};

template<class T>
struct iterator_traits<T*>
{
 typedef ptrdiff_t difference_type;
 typedef T value_type;
 typedef T* pointer;
 typedef T& reference;
 typedef random_access_iterator_tag iterator_category;
};

template<class T>
struct iterator_traits<const T*>
{
 typedef ptrdiff_t difference_type;
 typedef T value_type;
 typedef const T* pointer;
 typedef const T& reference;
 typedef random_access_iterator_tag iterator_category;
};

template<class Category, class T, class Distance = ptrdiff_t,
 class Pointer = T*, class Reference = T&>
struct iterator
{
 typedef T value_type;
 typedef Distance difference_type;
 typedef Pointer pointer;
 typedef Reference reference;
 typedef Category iterator_category;
};

struct input_iterator_tag {};
struct output_iterator_tag {};
struct forward_iterator_tag : public input_iterator_tag {};
struct bidirectional_iterator_tag : public forward_iterator_tag {};
struct random_access_iterator_tag : public bidirectional_iterator_tag {};

// 27.4.3, iterator operations
// extension: second argument not conforming to C++03
template <class InputIterator> // constexpr in C++17
 constexpr void advance(InputIterator& i,
 typename iterator_traits<InputIterator>::difference_type n);

template <class InputIterator> // constexpr in C++17
 constexpr typename iterator_traits<InputIterator>::difference_type
 distance(InputIterator first, InputIterator last);

template <class InputIterator> // constexpr in C++17
 constexpr InputIterator next(InputIterator x,
typename iterator_traits<InputIterator>::difference_type n = 1);

template <class BidirectionalIterator> // constexpr in C++17
 constexpr BidirectionalIterator prev(BidirectionalIterator x,
 typename iterator_traits<BidirectionalIterator>::difference_type n = 1); 

template <class Iterator>
class reverse_iterator
 : public iterator<typename iterator_traits<Iterator>::iterator_category,
 typename iterator_traits<Iterator>::value_type,
 typename iterator_traits<Iterator>::difference_type,
 typename iterator_traits<Iterator>::pointer,
 typename iterator_traits<Iterator>::reference>
{
protected:
 Iterator current;
public:
 typedef Iterator iterator_type;
 typedef typename iterator_traits<Iterator>::difference_type difference_type;
 typedef typename iterator_traits<Iterator>::reference reference;
 typedef typename iterator_traits<Iterator>::pointer pointer;

 constexpr reverse_iterator();
 constexpr explicit reverse_iterator(Iterator x);
 template <class U> constexpr reverse_iterator(const reverse_iterator<U>& u);
 template <class U> constexpr reverse_iterator& operator=(const reverse_iterator<U>& u);
 constexpr Iterator base() const;
 constexpr reference operator*() const;
 constexpr pointer operator->() const;
 constexpr reverse_iterator& operator++();
 constexpr reverse_iterator operator++(int);
 constexpr reverse_iterator& operator--();
 constexpr reverse_iterator operator--(int);
 constexpr reverse_iterator operator+ (difference_type n) const;
 constexpr reverse_iterator& operator+=(difference_type n);
 constexpr reverse_iterator operator- (difference_type n) const;
 constexpr reverse_iterator& operator-=(difference_type n);
 constexpr reference operator[](difference_type n) const;
};

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator==(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator<(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator!=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator>(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator>=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator<=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr auto
operator-(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y)
-> decltype(__y.base() - __x.base()); // constexpr in C++17

template <class Iterator>
constexpr reverse_iterator<Iterator>
operator+(typename reverse_iterator<Iterator>::difference_type n, 
 const reverse_iterator<Iterator>& x); // constexpr in C++17

template <class Iterator>
constexpr reverse_iterator<Iterator> make_reverse_iterator(Iterator i); // C++14, constexpr in C++17

template <class Container>
class back_insert_iterator
{
protected:
 Container* container;
public:
 typedef Container container_type;
 typedef void value_type;
 typedef void difference_type;
 typedef void reference;
 typedef void pointer;

 explicit back_insert_iterator(Container& x);
 back_insert_iterator& operator=(const typename Container::value_type& value);
 back_insert_iterator& operator*();
 back_insert_iterator& operator++();
 back_insert_iterator operator++(int);
};

template <class Container> back_insert_iterator<Container> back_inserter(Container& x);

template <class Container>
class front_insert_iterator
{
protected:
 Container* container;
public:
 typedef Container container_type;
 typedef void value_type;
 typedef void difference_type;
 typedef void reference;
 typedef void pointer;

 explicit front_insert_iterator(Container& x);
 front_insert_iterator& operator=(const typename Container::value_type& value);
 front_insert_iterator& operator*();
 front_insert_iterator& operator++();
 front_insert_iterator operator++(int);
};

template <class Container> front_insert_iterator<Container> front_inserter(Container& x);

template <class Container>
class insert_iterator
{
protected:
 Container* container;
 typename Container::iterator iter;
public:
 typedef Container container_type;
 typedef void value_type;
 typedef void difference_type;
 typedef void reference;
 typedef void pointer;

 insert_iterator(Container& x, typename Container::iterator i);
 insert_iterator& operator=(const typename Container::value_type& value);
 insert_iterator& operator*();
 insert_iterator& operator++();
 insert_iterator& operator++(int);
};

template <class Container, class Iterator>
insert_iterator<Container> inserter(Container& x, Iterator i);

template <class Iterator>
class move_iterator {
public:
 typedef Iterator iterator_type;
 typedef typename iterator_traits<Iterator>::difference_type difference_type;
 typedef Iterator pointer;
 typedef typename iterator_traits<Iterator>::value_type value_type;
 typedef typename iterator_traits<Iterator>::iterator_category iterator_category;
 typedef value_type&& reference;
 
 constexpr move_iterator(); // all the constexprs are in C++17
 constexpr explicit move_iterator(Iterator i);
 template <class U>
 constexpr move_iterator(const move_iterator<U>& u);
 template <class U>
 constexpr move_iterator& operator=(const move_iterator<U>& u);
 constexpr iterator_type base() const;
 constexpr reference operator*() const;
 constexpr pointer operator->() const;
 constexpr move_iterator& operator++();
 constexpr move_iterator operator++(int);
 constexpr move_iterator& operator--();
 constexpr move_iterator operator--(int);
 constexpr move_iterator operator+(difference_type n) const; 
 constexpr move_iterator& operator+=(difference_type n); 
 constexpr move_iterator operator-(difference_type n) const; 
 constexpr move_iterator& operator-=(difference_type n); 
 constexpr unspecified operator[](difference_type n) const;
private:
 Iterator current; // exposition only
};

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator==(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator!=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator<(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator<=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator>(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr bool // constexpr in C++17
operator>=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);

template <class Iterator1, class Iterator2>
constexpr auto // constexpr in C++17
operator-(const move_iterator<Iterator1>& x,
 const move_iterator<Iterator2>& y) -> decltype(x.base() - y.base());

template <class Iterator>
constexpr move_iterator<Iterator> operator+( // constexpr in C++17
 typename move_iterator<Iterator>::difference_type n, 
 const move_iterator<Iterator>& x);

template <class Iterator> // constexpr in C++17
constexpr move_iterator<Iterator> make_move_iterator(const Iterator& i);


template <class T, class charT = char, class traits = char_traits<charT>, class Distance = ptrdiff_t>
class istream_iterator
 : public iterator<input_iterator_tag, T, Distance, const T*, const T&>
{
public:
 typedef charT char_type;
 typedef traits traits_type;
 typedef basic_istream<charT,traits> istream_type;

 constexpr istream_iterator();
 istream_iterator(istream_type& s);
 istream_iterator(const istream_iterator& x);
 ~istream_iterator();

 const T& operator*() const;
 const T* operator->() const;
 istream_iterator& operator++();
 istream_iterator operator++(int);
};

template <class T, class charT, class traits, class Distance>
bool operator==(const istream_iterator<T,charT,traits,Distance>& x,
 const istream_iterator<T,charT,traits,Distance>& y);
template <class T, class charT, class traits, class Distance>
bool operator!=(const istream_iterator<T,charT,traits,Distance>& x,
 const istream_iterator<T,charT,traits,Distance>& y);

template <class T, class charT = char, class traits = char_traits<charT> >
class ostream_iterator
 : public iterator<output_iterator_tag, void, void, void ,void>
{
public:
 typedef charT char_type;
 typedef traits traits_type;
 typedef basic_ostream<charT,traits> ostream_type;

 ostream_iterator(ostream_type& s);
 ostream_iterator(ostream_type& s, const charT* delimiter);
 ostream_iterator(const ostream_iterator& x);
 ~ostream_iterator();
 ostream_iterator& operator=(const T& value);

 ostream_iterator& operator*();
 ostream_iterator& operator++();
 ostream_iterator& operator++(int);
};

template<class charT, class traits = char_traits<charT> >
class istreambuf_iterator
 : public iterator<input_iterator_tag, charT,
 typename traits::off_type, unspecified,
 charT>
{
public:
 typedef charT char_type;
 typedef traits traits_type;
 typedef typename traits::int_type int_type;
 typedef basic_streambuf<charT,traits> streambuf_type;
 typedef basic_istream<charT,traits> istream_type;

 istreambuf_iterator() noexcept;
 istreambuf_iterator(istream_type& s) noexcept;
 istreambuf_iterator(streambuf_type* s) noexcept;
 istreambuf_iterator(a-private-type) noexcept;

 charT operator*() const;
 pointer operator->() const;
 istreambuf_iterator& operator++();
 a-private-type operator++(int);

 bool equal(const istreambuf_iterator& b) const;
};

template <class charT, class traits>
bool operator==(const istreambuf_iterator<charT,traits>& a,
 const istreambuf_iterator<charT,traits>& b);
template <class charT, class traits>
bool operator!=(const istreambuf_iterator<charT,traits>& a,
 const istreambuf_iterator<charT,traits>& b);

template <class charT, class traits = char_traits<charT> >
class ostreambuf_iterator
 : public iterator<output_iterator_tag, void, void, void, void>
{
public:
 typedef charT char_type;
 typedef traits traits_type;
 typedef basic_streambuf<charT,traits> streambuf_type;
 typedef basic_ostream<charT,traits> ostream_type;

 ostreambuf_iterator(ostream_type& s) noexcept;
 ostreambuf_iterator(streambuf_type* s) noexcept;
 ostreambuf_iterator& operator=(charT c);
 ostreambuf_iterator& operator*();
 ostreambuf_iterator& operator++();
 ostreambuf_iterator& operator++(int);
 bool failed() const noexcept;
};

template <class C> constexpr auto begin(C& c) -> decltype(c.begin());
template <class C> constexpr auto begin(const C& c) -> decltype(c.begin());
template <class C> constexpr auto end(C& c) -> decltype(c.end());
template <class C> constexpr auto end(const C& c) -> decltype(c.end());
template <class T, size_t N> constexpr T* begin(T (&array)[N]);
template <class T, size_t N> constexpr T* end(T (&array)[N]);

template <class C> auto constexpr cbegin(const C& c) -> decltype(std::begin(c)); // C++14
template <class C> auto constexpr cend(const C& c) -> decltype(std::end(c)); // C++14
template <class C> auto constexpr rbegin(C& c) -> decltype(c.rbegin()); // C++14
template <class C> auto constexpr rbegin(const C& c) -> decltype(c.rbegin()); // C++14
template <class C> auto constexpr rend(C& c) -> decltype(c.rend()); // C++14
template <class C> constexpr auto rend(const C& c) -> decltype(c.rend()); // C++14
template <class E> reverse_iterator<const E*> constexpr rbegin(initializer_list<E> il); // C++14
template <class E> reverse_iterator<const E*> constexpr rend(initializer_list<E> il); // C++14
template <class T, size_t N> reverse_iterator<T*> constexpr rbegin(T (&array)[N]); // C++14
template <class T, size_t N> reverse_iterator<T*> constexpr rend(T (&array)[N]); // C++14
template <class C> constexpr auto crbegin(const C& c) -> decltype(std::rbegin(c)); // C++14
template <class C> constexpr auto crend(const C& c) -> decltype(std::rend(c)); // C++14

// 24.8, container access:
template <class C> constexpr auto size(const C& c) -> decltype(c.size()); // C++17
template <class T, size_t N> constexpr size_t size(const T (&array)[N]) noexcept; // C++17
template <class C> constexpr auto empty(const C& c) -> decltype(c.empty()); // C++17
template <class T, size_t N> constexpr bool empty(const T (&array)[N]) noexcept; // C++17
template <class E> constexpr bool empty(initializer_list<E> il) noexcept; // C++17
template <class C> constexpr auto data(C& c) -> decltype(c.data()); // C++17
template <class C> constexpr auto data(const C& c) -> decltype(c.data()); // C++17
template <class T, size_t N> constexpr T* data(T (&array)[N]) noexcept; // C++17
template <class E> constexpr const E* data(initializer_list<E> il) noexcept; // C++17

} // std

*/

#include <__config>
#include <iosfwd> // for forward declarations of vector and string.
#include <__functional_base>
#include <type_traits>
#include <cstddef>
#include <initializer_list>
#ifdef __APPLE__
#include <Availability.h>
#endif

#include <__debug>

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

_LIBCPP_BEGIN_NAMESPACE_STD

struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag : public input_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {};

template <class _Tp>
struct __has_iterator_category
{
private:
 struct __two {char __lx; char __lxx;};
 template <class _Up> static __two __test(...);
 template <class _Up> static char __test(typename _Up::iterator_category* = 0);
public:
 static const bool value = sizeof(__test<_Tp>(0)) == 1;
};

template <class _Iter, bool> struct __iterator_traits_impl {};

template <class _Iter>
struct __iterator_traits_impl<_Iter, true>
{
 typedef typename _Iter::difference_type difference_type;
 typedef typename _Iter::value_type value_type;
 typedef typename _Iter::pointer pointer;
 typedef typename _Iter::reference reference;
 typedef typename _Iter::iterator_category iterator_category;
};

template <class _Iter, bool> struct __iterator_traits {};

template <class _Iter>
struct __iterator_traits<_Iter, true>
 : __iterator_traits_impl
 <
 _Iter,
 is_convertible<typename _Iter::iterator_category, input_iterator_tag>::value ||
 is_convertible<typename _Iter::iterator_category, output_iterator_tag>::value
 >
{};

// iterator_traits<Iterator> will only have the nested types if Iterator::iterator_category
// exists. Else iterator_traits<Iterator> will be an empty class. This is a
// conforming extension which allows some programs to compile and behave as
// the client expects instead of failing at compile time.

template <class _Iter>
struct _LIBCPP_TEMPLATE_VIS iterator_traits
 : __iterator_traits<_Iter, __has_iterator_category<_Iter>::value> {};

template<class _Tp>
struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
{
 typedef ptrdiff_t difference_type;
 typedef typename remove_const<_Tp>::type value_type;
 typedef _Tp* pointer;
 typedef _Tp& reference;
 typedef random_access_iterator_tag iterator_category;
};

template <class _Tp, class _Up, bool = __has_iterator_category<iterator_traits<_Tp> >::value>
struct __has_iterator_category_convertible_to
 : public integral_constant<bool, is_convertible<typename iterator_traits<_Tp>::iterator_category, _Up>::value>
{};

template <class _Tp, class _Up>
struct __has_iterator_category_convertible_to<_Tp, _Up, false> : public false_type {};

template <class _Tp>
struct __is_input_iterator : public __has_iterator_category_convertible_to<_Tp, input_iterator_tag> {};

template <class _Tp>
struct __is_forward_iterator : public __has_iterator_category_convertible_to<_Tp, forward_iterator_tag> {};

template <class _Tp>
struct __is_bidirectional_iterator : public __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag> {};

template <class _Tp>
struct __is_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {};

template <class _Tp>
struct __is_exactly_input_iterator
 : public integral_constant<bool, 
 __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value && 
 !__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};

template<class _Category, class _Tp, class _Distance = ptrdiff_t,
 class _Pointer = _Tp*, class _Reference = _Tp&>
struct _LIBCPP_TEMPLATE_VIS iterator
{
 typedef _Tp value_type;
 typedef _Distance difference_type;
 typedef _Pointer pointer;
 typedef _Reference reference;
 typedef _Category iterator_category;
};

template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
void __advance(_InputIter& __i,
 typename iterator_traits<_InputIter>::difference_type __n, input_iterator_tag)
{
 for (; __n > 0; --__n)
 ++__i;
}

template <class _BiDirIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
void __advance(_BiDirIter& __i,
 typename iterator_traits<_BiDirIter>::difference_type __n, bidirectional_iterator_tag)
{
 if (__n >= 0)
 for (; __n > 0; --__n)
 ++__i;
 else
 for (; __n < 0; ++__n)
 --__i;
}

template <class _RandIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
void __advance(_RandIter& __i,
 typename iterator_traits<_RandIter>::difference_type __n, random_access_iterator_tag)
{
 __i += __n;
}

template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
void advance(_InputIter& __i,
 typename iterator_traits<_InputIter>::difference_type __n)
{
 __advance(__i, __n, typename iterator_traits<_InputIter>::iterator_category());
}

template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename iterator_traits<_InputIter>::difference_type
__distance(_InputIter __first, _InputIter __last, input_iterator_tag)
{
 typename iterator_traits<_InputIter>::difference_type __r(0);
 for (; __first != __last; ++__first)
 ++__r;
 return __r;
}

template <class _RandIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename iterator_traits<_RandIter>::difference_type
__distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
{
 return __last - __first;
}

template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename iterator_traits<_InputIter>::difference_type
distance(_InputIter __first, _InputIter __last)
{
 return __distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
}

template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_InputIter
next(_InputIter __x,
 typename iterator_traits<_InputIter>::difference_type __n = 1,
 typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0)
{
 _VSTD::advance(__x, __n);
 return __x;
}

template <class _BidiretionalIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_BidiretionalIter
prev(_BidiretionalIter __x,
 typename iterator_traits<_BidiretionalIter>::difference_type __n = 1,
 typename enable_if<__is_bidirectional_iterator<_BidiretionalIter>::value>::type* = 0)
{
 _VSTD::advance(__x, -__n);
 return __x;
}


template <class _Tp, class = void>
struct __is_stashing_iterator : false_type {};

template <class _Tp>
struct __is_stashing_iterator<_Tp, typename __void_t<typename _Tp::__stashing_iterator_tag>::type>
 : true_type {};

template <class _Iter>
class _LIBCPP_TEMPLATE_VIS reverse_iterator
 : public iterator<typename iterator_traits<_Iter>::iterator_category,
 typename iterator_traits<_Iter>::value_type,
 typename iterator_traits<_Iter>::difference_type,
 typename iterator_traits<_Iter>::pointer,
 typename iterator_traits<_Iter>::reference>
{
private:
 /*mutable*/ _Iter __t; // no longer used as of LWG #2360, not removed due to ABI break

 static_assert(!__is_stashing_iterator<_Iter>::value,
 "The specified iterator type cannot be used with reverse_iterator; "
 "Using stashing iterators with reverse_iterator causes undefined behavior");

protected:
 _Iter current;
public:
 typedef _Iter iterator_type;
 typedef typename iterator_traits<_Iter>::difference_type difference_type;
 typedef typename iterator_traits<_Iter>::reference reference;
 typedef typename iterator_traits<_Iter>::pointer pointer;

 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator() : __t(), current() {}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 explicit reverse_iterator(_Iter __x) : __t(__x), current(__x) {}
 template <class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator(const reverse_iterator<_Up>& __u) : __t(__u.base()), current(__u.base()) {}
 template <class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator& operator=(const reverse_iterator<_Up>& __u)
 { __t = current = __u.base(); return *this; }
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 _Iter base() const {return current;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reference operator*() const {_Iter __tmp = current; return *--__tmp;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 pointer operator->() const {return _VSTD::addressof(operator*());}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator& operator++() {--current; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator operator++(int) {reverse_iterator __tmp(*this); --current; return __tmp;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator& operator--() {++current; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator operator--(int) {reverse_iterator __tmp(*this); ++current; return __tmp;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator operator+ (difference_type __n) const {return reverse_iterator(current - __n);}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator& operator+=(difference_type __n) {current -= __n; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator operator- (difference_type __n) const {return reverse_iterator(current + __n);}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator& operator-=(difference_type __n) {current += __n; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reference operator[](difference_type __n) const {return *(*this + __n);}
};

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() == __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() > __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() != __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() < __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() <= __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __x.base() >= __y.base();
}

#ifndef _LIBCPP_CXX03_LANG
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
-> decltype(__y.base() - __x.base())
{
 return __y.base() - __x.base();
}
#else
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
typename reverse_iterator<_Iter1>::difference_type
operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
{
 return __y.base() - __x.base();
}
#endif

template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<_Iter>
operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x)
{
 return reverse_iterator<_Iter>(__x.base() - __n);
}

#if _LIBCPP_STD_VER > 11
template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<_Iter> make_reverse_iterator(_Iter __i)
{
 return reverse_iterator<_Iter>(__i);
}
#endif

template <class _Container>
class _LIBCPP_TEMPLATE_VIS back_insert_iterator
 : public iterator<output_iterator_tag,
 void,
 void,
 void,
 void>
{
protected:
 _Container* container;
public:
 typedef _Container container_type;

 _LIBCPP_INLINE_VISIBILITY explicit back_insert_iterator(_Container& __x) : container(_VSTD::addressof(__x)) {}
 _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator=(const typename _Container::value_type& __value_)
 {container->push_back(__value_); return *this;}
#ifndef _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator=(typename _Container::value_type&& __value_)
 {container->push_back(_VSTD::move(__value_)); return *this;}
#endif // _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator*() {return *this;}
 _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator++() {return *this;}
 _LIBCPP_INLINE_VISIBILITY back_insert_iterator operator++(int) {return *this;}
};

template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
back_insert_iterator<_Container>
back_inserter(_Container& __x)
{
 return back_insert_iterator<_Container>(__x);
}

template <class _Container>
class _LIBCPP_TEMPLATE_VIS front_insert_iterator
 : public iterator<output_iterator_tag,
 void,
 void,
 void,
 void>
{
protected:
 _Container* container;
public:
 typedef _Container container_type;

 _LIBCPP_INLINE_VISIBILITY explicit front_insert_iterator(_Container& __x) : container(_VSTD::addressof(__x)) {}
 _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator=(const typename _Container::value_type& __value_)
 {container->push_front(__value_); return *this;}
#ifndef _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator=(typename _Container::value_type&& __value_)
 {container->push_front(_VSTD::move(__value_)); return *this;}
#endif // _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator*() {return *this;}
 _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator++() {return *this;}
 _LIBCPP_INLINE_VISIBILITY front_insert_iterator operator++(int) {return *this;}
};

template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
front_insert_iterator<_Container>
front_inserter(_Container& __x)
{
 return front_insert_iterator<_Container>(__x);
}

template <class _Container>
class _LIBCPP_TEMPLATE_VIS insert_iterator
 : public iterator<output_iterator_tag,
 void,
 void,
 void,
 void>
{
protected:
 _Container* container;
 typename _Container::iterator iter;
public:
 typedef _Container container_type;

 _LIBCPP_INLINE_VISIBILITY insert_iterator(_Container& __x, typename _Container::iterator __i)
 : container(_VSTD::addressof(__x)), iter(__i) {}
 _LIBCPP_INLINE_VISIBILITY insert_iterator& operator=(const typename _Container::value_type& __value_)
 {iter = container->insert(iter, __value_); ++iter; return *this;}
#ifndef _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY insert_iterator& operator=(typename _Container::value_type&& __value_)
 {iter = container->insert(iter, _VSTD::move(__value_)); ++iter; return *this;}
#endif // _LIBCPP_CXX03_LANG
 _LIBCPP_INLINE_VISIBILITY insert_iterator& operator*() {return *this;}
 _LIBCPP_INLINE_VISIBILITY insert_iterator& operator++() {return *this;}
 _LIBCPP_INLINE_VISIBILITY insert_iterator& operator++(int) {return *this;}
};

template <class _Container>
inline _LIBCPP_INLINE_VISIBILITY
insert_iterator<_Container>
inserter(_Container& __x, typename _Container::iterator __i)
{
 return insert_iterator<_Container>(__x, __i);
}

template <class _Tp, class _CharT = char,
 class _Traits = char_traits<_CharT>, class _Distance = ptrdiff_t>
class _LIBCPP_TEMPLATE_VIS istream_iterator
 : public iterator<input_iterator_tag, _Tp, _Distance, const _Tp*, const _Tp&>
{
public:
 typedef _CharT char_type;
 typedef _Traits traits_type;
 typedef basic_istream<_CharT,_Traits> istream_type;
private:
 istream_type* __in_stream_;
 _Tp __value_;
public:
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istream_iterator() : __in_stream_(0), __value_() {}
 _LIBCPP_INLINE_VISIBILITY istream_iterator(istream_type& __s) : __in_stream_(_VSTD::addressof(__s))
 {
 if (!(*__in_stream_ >> __value_))
 __in_stream_ = 0;
 }

 _LIBCPP_INLINE_VISIBILITY const _Tp& operator*() const {return __value_;}
 _LIBCPP_INLINE_VISIBILITY const _Tp* operator->() const {return _VSTD::addressof((operator*()));}
 _LIBCPP_INLINE_VISIBILITY istream_iterator& operator++()
 {
 if (!(*__in_stream_ >> __value_))
 __in_stream_ = 0;
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY istream_iterator operator++(int)
 {istream_iterator __t(*this); ++(*this); return __t;}

 friend _LIBCPP_INLINE_VISIBILITY
 bool operator==(const istream_iterator& __x, const istream_iterator& __y)
 {return __x.__in_stream_ == __y.__in_stream_;}

 friend _LIBCPP_INLINE_VISIBILITY
 bool operator!=(const istream_iterator& __x, const istream_iterator& __y)
 {return !(__x == __y);}
};

template <class _Tp, class _CharT = char, class _Traits = char_traits<_CharT> >
class _LIBCPP_TEMPLATE_VIS ostream_iterator
 : public iterator<output_iterator_tag, void, void, void, void>
{
public:
 typedef _CharT char_type;
 typedef _Traits traits_type;
 typedef basic_ostream<_CharT,_Traits> ostream_type;
private:
 ostream_type* __out_stream_;
 const char_type* __delim_;
public:
 _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s) _NOEXCEPT
 : __out_stream_(_VSTD::addressof(__s)), __delim_(0) {}
 _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s, const _CharT* __delimiter) _NOEXCEPT
 : __out_stream_(_VSTD::addressof(__s)), __delim_(__delimiter) {}
 _LIBCPP_INLINE_VISIBILITY ostream_iterator& operator=(const _Tp& __value_)
 {
 *__out_stream_ << __value_;
 if (__delim_)
 *__out_stream_ << __delim_;
 return *this;
 }

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

template<class _CharT, class _Traits>
class _LIBCPP_TEMPLATE_VIS istreambuf_iterator
 : public iterator<input_iterator_tag, _CharT,
 typename _Traits::off_type, _CharT*,
 _CharT>
{
public:
 typedef _CharT char_type;
 typedef _Traits traits_type;
 typedef typename _Traits::int_type int_type;
 typedef basic_streambuf<_CharT,_Traits> streambuf_type;
 typedef basic_istream<_CharT,_Traits> istream_type;
private:
 mutable streambuf_type* __sbuf_;

 class __proxy
 {
 char_type __keep_;
 streambuf_type* __sbuf_;
 _LIBCPP_INLINE_VISIBILITY __proxy(char_type __c, streambuf_type* __s)
 : __keep_(__c), __sbuf_(__s) {}
 friend class istreambuf_iterator;
 public:
 _LIBCPP_INLINE_VISIBILITY char_type operator*() const {return __keep_;}
 };

 _LIBCPP_INLINE_VISIBILITY
 bool __test_for_eof() const
 {
 if (__sbuf_ && traits_type::eq_int_type(__sbuf_->sgetc(), traits_type::eof()))
 __sbuf_ = 0;
 return __sbuf_ == 0;
 }
public:
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istreambuf_iterator() _NOEXCEPT : __sbuf_(0) {}
 _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(istream_type& __s) _NOEXCEPT
 : __sbuf_(__s.rdbuf()) {}
 _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(streambuf_type* __s) _NOEXCEPT
 : __sbuf_(__s) {}
 _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(const __proxy& __p) _NOEXCEPT
 : __sbuf_(__p.__sbuf_) {}

 _LIBCPP_INLINE_VISIBILITY char_type operator*() const
 {return static_cast<char_type>(__sbuf_->sgetc());}
 _LIBCPP_INLINE_VISIBILITY istreambuf_iterator& operator++()
 {
 __sbuf_->sbumpc();
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY __proxy operator++(int)
 {
 return __proxy(__sbuf_->sbumpc(), __sbuf_);
 }

 _LIBCPP_INLINE_VISIBILITY bool equal(const istreambuf_iterator& __b) const
 {return __test_for_eof() == __b.__test_for_eof();}
};

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool operator==(const istreambuf_iterator<_CharT,_Traits>& __a,
 const istreambuf_iterator<_CharT,_Traits>& __b)
 {return __a.equal(__b);}

template <class _CharT, class _Traits>
inline _LIBCPP_INLINE_VISIBILITY
bool operator!=(const istreambuf_iterator<_CharT,_Traits>& __a,
 const istreambuf_iterator<_CharT,_Traits>& __b)
 {return !__a.equal(__b);}

template <class _CharT, class _Traits>
class _LIBCPP_TEMPLATE_VIS ostreambuf_iterator
 : public iterator<output_iterator_tag, void, void, void, void>
{
public:
 typedef _CharT char_type;
 typedef _Traits traits_type;
 typedef basic_streambuf<_CharT,_Traits> streambuf_type;
 typedef basic_ostream<_CharT,_Traits> ostream_type;
private:
 streambuf_type* __sbuf_;
public:
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(ostream_type& __s) _NOEXCEPT
 : __sbuf_(__s.rdbuf()) {}
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(streambuf_type* __s) _NOEXCEPT
 : __sbuf_(__s) {}
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator=(_CharT __c)
 {
 if (__sbuf_ && traits_type::eq_int_type(__sbuf_->sputc(__c), traits_type::eof()))
 __sbuf_ = 0;
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator*() {return *this;}
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator++() {return *this;}
 _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator++(int) {return *this;}
 _LIBCPP_INLINE_VISIBILITY bool failed() const _NOEXCEPT {return __sbuf_ == 0;}

#if !defined(__APPLE__) || \
 (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED > __MAC_10_8) || \
 (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED > __IPHONE_6_0)

 template <class _Ch, class _Tr>
 friend
 _LIBCPP_HIDDEN
 ostreambuf_iterator<_Ch, _Tr>
 __pad_and_output(ostreambuf_iterator<_Ch, _Tr> __s,
 const _Ch* __ob, const _Ch* __op, const _Ch* __oe,
 ios_base& __iob, _Ch __fl);
#endif
};

template <class _Iter>
class _LIBCPP_TEMPLATE_VIS move_iterator
{
private:
 _Iter __i;
public:
 typedef _Iter iterator_type;
 typedef typename iterator_traits<iterator_type>::iterator_category iterator_category;
 typedef typename iterator_traits<iterator_type>::value_type value_type;
 typedef typename iterator_traits<iterator_type>::difference_type difference_type;
 typedef iterator_type pointer;
#ifndef _LIBCPP_CXX03_LANG
 typedef typename iterator_traits<iterator_type>::reference __reference;
 typedef typename conditional<
 is_reference<__reference>::value,
 typename remove_reference<__reference>::type&&,
 __reference
 >::type reference;
#else
 typedef typename iterator_traits<iterator_type>::reference reference;
#endif

 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator() : __i() {}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 explicit move_iterator(_Iter __x) : __i(__x) {}
 template <class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator(const move_iterator<_Up>& __u) : __i(__u.base()) {}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 _Iter base() const {return __i;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 
 reference operator*() const { return static_cast<reference>(*__i); }
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 pointer operator->() const { return __i;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator& operator++() {++__i; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator operator++(int) {move_iterator __tmp(*this); ++__i; return __tmp;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator& operator--() {--__i; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator operator--(int) {move_iterator __tmp(*this); --__i; return __tmp;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator operator+ (difference_type __n) const {return move_iterator(__i + __n);}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator& operator+=(difference_type __n) {__i += __n; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator operator- (difference_type __n) const {return move_iterator(__i - __n);}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator& operator-=(difference_type __n) {__i -= __n; return *this;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reference operator[](difference_type __n) const { return static_cast<reference>(__i[__n]); }
};

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator==(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() == __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator<(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() < __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator!=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() != __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator>(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() > __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator>=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() >= __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
bool
operator<=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() <= __y.base();
}

#ifndef _LIBCPP_CXX03_LANG
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
operator-(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
-> decltype(__x.base() - __y.base())
{
 return __x.base() - __y.base();
}
#else
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
typename move_iterator<_Iter1>::difference_type
operator-(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
{
 return __x.base() - __y.base();
}
#endif

template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
move_iterator<_Iter>
operator+(typename move_iterator<_Iter>::difference_type __n, const move_iterator<_Iter>& __x)
{
 return move_iterator<_Iter>(__x.base() + __n);
}

template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
move_iterator<_Iter>
make_move_iterator(_Iter __i)
{
 return move_iterator<_Iter>(__i);
}

// __wrap_iter

template <class _Iter> class __wrap_iter;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
bool
operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

#ifndef _LIBCPP_CXX03_LANG
template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
auto
operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
-> decltype(__x.base() - __y.base());
#else
template <class _Iter1, class _Iter2>
_LIBCPP_INLINE_VISIBILITY
typename __wrap_iter<_Iter1>::difference_type
operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
#endif

template <class _Iter>
_LIBCPP_INLINE_VISIBILITY
__wrap_iter<_Iter>
operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOEXCEPT_DEBUG;

template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY copy(_Ip, _Ip, _Op);
template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY copy_backward(_B1, _B1, _B2);
template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY move(_Ip, _Ip, _Op);
template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY move_backward(_B1, _B1, _B2);

#if _LIBCPP_DEBUG_LEVEL < 2

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
 is_trivially_copy_assignable<_Tp>::value,
 _Tp*
>::type
__unwrap_iter(__wrap_iter<_Tp*>);

#else

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
 is_trivially_copy_assignable<_Tp>::value,
 __wrap_iter<_Tp*>
>::type
__unwrap_iter(__wrap_iter<_Tp*> __i);

#endif

template <class _Iter>
class __wrap_iter
{
public:
 typedef _Iter iterator_type;
 typedef typename iterator_traits<iterator_type>::iterator_category iterator_category;
 typedef typename iterator_traits<iterator_type>::value_type value_type;
 typedef typename iterator_traits<iterator_type>::difference_type difference_type;
 typedef typename iterator_traits<iterator_type>::pointer pointer;
 typedef typename iterator_traits<iterator_type>::reference reference;
private:
 iterator_type __i;
public:
 _LIBCPP_INLINE_VISIBILITY __wrap_iter() _NOEXCEPT_DEBUG
#if _LIBCPP_STD_VER > 11
 : __i{}
#endif
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__insert_i(this);
#endif
 }
 template <class _Up> _LIBCPP_INLINE_VISIBILITY __wrap_iter(const __wrap_iter<_Up>& __u,
 typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = 0) _NOEXCEPT_DEBUG
 : __i(__u.base())
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 __get_db()->__iterator_copy(this, &__u);
#endif
 }
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_INLINE_VISIBILITY
 __wrap_iter(const __wrap_iter& __x)
 : __i(__x.base())
 {
 __get_db()->__iterator_copy(this, &__x);
 }
 _LIBCPP_INLINE_VISIBILITY
 __wrap_iter& operator=(const __wrap_iter& __x)
 {
 if (this != &__x)
 {
 __get_db()->__iterator_copy(this, &__x);
 __i = __x.__i;
 }
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY
 ~__wrap_iter()
 {
 __get_db()->__erase_i(this);
 }
#endif
 _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
 "Attempted to dereference a non-dereferenceable iterator");
#endif
 return *__i;
 }
 _LIBCPP_INLINE_VISIBILITY pointer operator->() const _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
 "Attempted to dereference a non-dereferenceable iterator");
#endif
 return (pointer)_VSTD::addressof(*__i);
 }
 _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator++() _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
 "Attempted to increment non-incrementable iterator");
#endif
 ++__i;
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY __wrap_iter operator++(int) _NOEXCEPT_DEBUG
 {__wrap_iter __tmp(*this); ++(*this); return __tmp;}
 _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator--() _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__decrementable(this),
 "Attempted to decrement non-decrementable iterator");
#endif
 --__i;
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY __wrap_iter operator--(int) _NOEXCEPT_DEBUG
 {__wrap_iter __tmp(*this); --(*this); return __tmp;}
 _LIBCPP_INLINE_VISIBILITY __wrap_iter operator+ (difference_type __n) const _NOEXCEPT_DEBUG
 {__wrap_iter __w(*this); __w += __n; return __w;}
 _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator+=(difference_type __n) _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__addable(this, __n),
 "Attempted to add/subtract iterator outside of valid range");
#endif
 __i += __n;
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY __wrap_iter operator- (difference_type __n) const _NOEXCEPT_DEBUG
 {return *this + (-__n);}
 _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator-=(difference_type __n) _NOEXCEPT_DEBUG
 {*this += -__n; return *this;}
 _LIBCPP_INLINE_VISIBILITY reference operator[](difference_type __n) const _NOEXCEPT_DEBUG
 {
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__subscriptable(this, __n),
 "Attempted to subscript iterator outside of valid range");
#endif
 return __i[__n];
 }

 _LIBCPP_INLINE_VISIBILITY iterator_type base() const _NOEXCEPT_DEBUG {return __i;}

private:
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_INLINE_VISIBILITY __wrap_iter(const void* __p, iterator_type __x) : __i(__x)
 {
 __get_db()->__insert_ic(this, __p);
 }
#else
 _LIBCPP_INLINE_VISIBILITY __wrap_iter(iterator_type __x) _NOEXCEPT_DEBUG : __i(__x) {}
#endif

 template <class _Up> friend class __wrap_iter;
 template <class _CharT, class _Traits, class _Alloc> friend class basic_string;
 template <class _Tp, class _Alloc> friend class _LIBCPP_TEMPLATE_VIS vector;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

 template <class _Iter1, class _Iter2>
 friend
 bool
 operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;

#ifndef _LIBCPP_CXX03_LANG
 template <class _Iter1, class _Iter2>
 friend
 auto
 operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 -> decltype(__x.base() - __y.base());
#else
 template <class _Iter1, class _Iter2>
 friend
 typename __wrap_iter<_Iter1>::difference_type
 operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
#endif

 template <class _Iter1>
 friend
 __wrap_iter<_Iter1>
 operator+(typename __wrap_iter<_Iter1>::difference_type, __wrap_iter<_Iter1>) _NOEXCEPT_DEBUG;

 template <class _Ip, class _Op> friend _Op copy(_Ip, _Ip, _Op);
 template <class _B1, class _B2> friend _B2 copy_backward(_B1, _B1, _B2);
 template <class _Ip, class _Op> friend _Op move(_Ip, _Ip, _Op);
 template <class _B1, class _B2> friend _B2 move_backward(_B1, _B1, _B2);

#if _LIBCPP_DEBUG_LEVEL < 2
 template <class _Tp>
 friend
 typename enable_if
 <
 is_trivially_copy_assignable<_Tp>::value,
 _Tp*
 >::type
 __unwrap_iter(__wrap_iter<_Tp*>);
#else
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
 is_trivially_copy_assignable<_Tp>::value,
 __wrap_iter<_Tp*>
 >::type
 __unwrap_iter(__wrap_iter<_Tp*> __i);
#endif
};

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
 return __x.base() == __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
 "Attempted to compare incomparable iterators");
#endif
 return __x.base() < __y.base();
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
 return !(__x == __y);
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
 return __y < __x;
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
 return !(__x < __y);
}

template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
 return !(__y < __x);
}

template <class _Iter1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
{
 return !(__x == __y);
}

template <class _Iter1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
{
 return __y < __x;
}

template <class _Iter1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
{
 return !(__x < __y);
}

template <class _Iter1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
{
 return !(__y < __x);
}

#ifndef _LIBCPP_CXX03_LANG
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
auto
operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
-> decltype(__x.base() - __y.base())
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
 "Attempted to subtract incompatible iterators");
#endif
 return __x.base() - __y.base();
}
#else
template <class _Iter1, class _Iter2>
inline _LIBCPP_INLINE_VISIBILITY
typename __wrap_iter<_Iter1>::difference_type
operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
{
#if _LIBCPP_DEBUG_LEVEL >= 2
 _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
 "Attempted to subtract incompatible iterators");
#endif
 return __x.base() - __y.base();
}
#endif

template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY
__wrap_iter<_Iter>
operator+(typename __wrap_iter<_Iter>::difference_type __n,
 __wrap_iter<_Iter> __x) _NOEXCEPT_DEBUG
{
 __x += __n;
 return __x;
}

template <class _Iter>
struct __libcpp_is_trivial_iterator
 : public _LIBCPP_BOOL_CONSTANT(is_pointer<_Iter>::value) {};
 
template <class _Iter>
struct __libcpp_is_trivial_iterator<move_iterator<_Iter> >
 : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};

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

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


template <class _Tp, size_t _Np>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
_Tp*
begin(_Tp (&__array)[_Np])
{
 return __array;
}

template <class _Tp, size_t _Np>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
_Tp*
end(_Tp (&__array)[_Np])
{
 return __array + _Np;
}

#if !defined(_LIBCPP_CXX03_LANG)

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
begin(_Cp& __c) -> decltype(__c.begin())
{
 return __c.begin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
begin(const _Cp& __c) -> decltype(__c.begin())
{
 return __c.begin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
end(_Cp& __c) -> decltype(__c.end())
{
 return __c.end();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto
end(const _Cp& __c) -> decltype(__c.end())
{
 return __c.end();
}

#if _LIBCPP_STD_VER > 11

template <class _Tp, size_t _Np>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<_Tp*> rbegin(_Tp (&__array)[_Np])
{
 return reverse_iterator<_Tp*>(__array + _Np);
}

template <class _Tp, size_t _Np>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<_Tp*> rend(_Tp (&__array)[_Np])
{
 return reverse_iterator<_Tp*>(__array);
}

template <class _Ep>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<const _Ep*> rbegin(initializer_list<_Ep> __il)
{
 return reverse_iterator<const _Ep*>(__il.end());
}

template <class _Ep>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator<const _Ep*> rend(initializer_list<_Ep> __il)
{
 return reverse_iterator<const _Ep*>(__il.begin());
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
auto cbegin(const _Cp& __c) -> decltype(_VSTD::begin(__c))
{
 return _VSTD::begin(__c);
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
auto cend(const _Cp& __c) -> decltype(_VSTD::end(__c))
{
 return _VSTD::end(__c);
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto rbegin(_Cp& __c) -> decltype(__c.rbegin())
{
 return __c.rbegin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto rbegin(const _Cp& __c) -> decltype(__c.rbegin())
{
 return __c.rbegin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto rend(_Cp& __c) -> decltype(__c.rend())
{
 return __c.rend();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto rend(const _Cp& __c) -> decltype(__c.rend())
{
 return __c.rend();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto crbegin(const _Cp& __c) -> decltype(_VSTD::rbegin(__c))
{
 return _VSTD::rbegin(__c);
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
auto crend(const _Cp& __c) -> decltype(_VSTD::rend(__c))
{
 return _VSTD::rend(__c);
}

#endif


#else // defined(_LIBCPP_CXX03_LANG)

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY
typename _Cp::iterator
begin(_Cp& __c)
{
 return __c.begin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY
typename _Cp::const_iterator
begin(const _Cp& __c)
{
 return __c.begin();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY
typename _Cp::iterator
end(_Cp& __c)
{
 return __c.end();
}

template <class _Cp>
inline _LIBCPP_INLINE_VISIBILITY
typename _Cp::const_iterator
end(const _Cp& __c)
{
 return __c.end();
}

#endif // !defined(_LIBCPP_CXX03_LANG)

#if _LIBCPP_STD_VER > 14
template <class _Cont>
constexpr auto size(const _Cont& __c) -> decltype(__c.size()) { return __c.size(); }

template <class _Tp, size_t _Sz>
constexpr size_t size(const _Tp (&)[_Sz]) noexcept { return _Sz; }

template <class _Cont>
constexpr auto empty(const _Cont& __c) -> decltype(__c.empty()) { return __c.empty(); }

template <class _Tp, size_t _Sz>
constexpr bool empty(const _Tp (&)[_Sz]) noexcept { return false; }

template <class _Ep>
constexpr bool empty(initializer_list<_Ep> __il) noexcept { return __il.size() == 0; }

template <class _Cont> constexpr
auto data(_Cont& __c) -> decltype(__c.data()) { return __c.data(); }

template <class _Cont> constexpr
auto data(const _Cont& __c) -> decltype(__c.data()) { return __c.data(); }

template <class _Tp, size_t _Sz>
constexpr _Tp* data(_Tp (&__array)[_Sz]) noexcept { return __array; }

template <class _Ep>
constexpr const _Ep* data(initializer_list<_Ep> __il) noexcept { return __il.begin(); }
#endif


_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_ITERATOR