STL/stl/inc/iterator

// iterator standard header

// Copyright (c) Microsoft Corporation.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#pragma once
#ifndef _ITERATOR_
#define _ITERATOR_
#include <yvals_core.h>
#if _STL_COMPILER_PREPROCESSOR
#include <iosfwd>
#include <xutility>

#pragma pack(push, _CRT_PACKING)
#pragma warning(push, _STL_WARNING_LEVEL)
#pragma warning(disable : _STL_DISABLED_WARNINGS)
_STL_DISABLE_CLANG_WARNINGS
#pragma push_macro("new")
#undef new

_STD_BEGIN
// CLASS TEMPLATE back_insert_iterator
template <class _Container>
class back_insert_iterator { // wrap pushes to back of container as output iterator
public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using pointer           = void;
    using reference         = void;

    using container_type = _Container;

#ifdef __cpp_lib_concepts
    using difference_type = ptrdiff_t;

    constexpr back_insert_iterator() noexcept = default;
#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
    using difference_type = void;
#endif // __cpp_lib_concepts

    explicit back_insert_iterator(_Container& _Cont) noexcept /* strengthened */ : container(_STD addressof(_Cont)) {}

    back_insert_iterator& operator=(const typename _Container::value_type& _Val) {
        container->push_back(_Val);
        return *this;
    }

    back_insert_iterator& operator=(typename _Container::value_type&& _Val) {
        container->push_back(_STD move(_Val));
        return *this;
    }

    _NODISCARD back_insert_iterator& operator*() noexcept /* strengthened */ {
        return *this;
    }

    back_insert_iterator& operator++() noexcept /* strengthened */ {
        return *this;
    }

    back_insert_iterator operator++(int) noexcept /* strengthened */ {
        return *this;
    }

protected:
    _Container* container = nullptr;
};

// FUNCTION TEMPLATE back_inserter
template <class _Container>
_NODISCARD back_insert_iterator<_Container> back_inserter(_Container& _Cont) noexcept /* strengthened */ {
    // return a back_insert_iterator
    return back_insert_iterator<_Container>(_Cont);
}

// CLASS TEMPLATE front_insert_iterator
template <class _Container>
class front_insert_iterator { // wrap pushes to front of container as output iterator
public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using pointer           = void;
    using reference         = void;

    using container_type = _Container;

#ifdef __cpp_lib_concepts
    using difference_type = ptrdiff_t;

    constexpr front_insert_iterator() noexcept = default;
#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
    using difference_type = void;
#endif // __cpp_lib_concepts

    explicit front_insert_iterator(_Container& _Cont) : container(_STD addressof(_Cont)) {}

    front_insert_iterator& operator=(const typename _Container::value_type& _Val) { // push value into container
        container->push_front(_Val);
        return *this;
    }

    front_insert_iterator& operator=(typename _Container::value_type&& _Val) { // push value into container
        container->push_front(_STD move(_Val));
        return *this;
    }

    _NODISCARD front_insert_iterator& operator*() { // pretend to return designated value
        return *this;
    }

    front_insert_iterator& operator++() { // pretend to preincrement
        return *this;
    }

    front_insert_iterator operator++(int) { // pretend to postincrement
        return *this;
    }

protected:
    _Container* container = nullptr;
};

// FUNCTION TEMPLATE front_inserter
template <class _Container>
_NODISCARD front_insert_iterator<_Container> front_inserter(_Container& _Cont) {
    return front_insert_iterator<_Container>(_Cont);
}


// CLASS TEMPLATE insert_iterator
template <class _Container>
class insert_iterator { // wrap inserts into container as output iterator
public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using pointer           = void;
    using reference         = void;

    using container_type = _Container;

#ifdef __cpp_lib_concepts
    using difference_type = ptrdiff_t;

    insert_iterator() = default;
#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
    using difference_type = void;
#endif // __cpp_lib_concepts

    insert_iterator(_Container& _Cont, typename _Container::iterator _Where)
        : container(_STD addressof(_Cont)), iter(_Where) {}

    insert_iterator& operator=(
        const typename _Container::value_type& _Val) { // insert into container and increment stored iterator
        iter = container->insert(iter, _Val);
        ++iter;
        return *this;
    }

    insert_iterator& operator=(typename _Container::value_type&& _Val) { // push value into container

        iter = container->insert(iter, _STD move(_Val));
        ++iter;
        return *this;
    }

    _NODISCARD insert_iterator& operator*() { // pretend to return designated value
        return *this;
    }

    insert_iterator& operator++() { // pretend to preincrement
        return *this;
    }

    insert_iterator& operator++(int) { // pretend to postincrement
        return *this;
    }

protected:
    _Container* container = nullptr;
    typename _Container::iterator iter{};
};

// FUNCTION TEMPLATE inserter
template <class _Container>
_NODISCARD insert_iterator<_Container> inserter(_Container& _Cont, typename _Container::iterator _Where) {
    return insert_iterator<_Container>(_Cont, _Where);
}


// CLASS TEMPLATE istream_iterator
template <class _Ty, class _Elem = char, class _Traits = char_traits<_Elem>, class _Diff = ptrdiff_t>
class istream_iterator { // wrap _Ty extracts from input stream as input iterator
public:
    using iterator_category = input_iterator_tag;
    using value_type        = _Ty;
    using difference_type   = _Diff;
    using pointer           = const _Ty*;
    using reference         = const _Ty&;

    using char_type    = _Elem;
    using traits_type  = _Traits;
    using istream_type = basic_istream<_Elem, _Traits>;

    static_assert(conjunction_v<is_default_constructible<_Ty>, is_copy_constructible<_Ty>, is_copy_assignable<_Ty>>,
        "istream_iterator<T> requires T to be default constructible, copy constructible, and copy assignable. "
        "(N4835 [istream.iterator]/2)");

    constexpr istream_iterator() {}

    istream_iterator(istream_type& _Istr) : _Myistr(_STD addressof(_Istr)) {
        _Getval();
    }

    _NODISCARD const _Ty& operator*() const {
        _STL_ASSERT(_Myistr, "The stored stream pointer in_stream must be non-null");
        return _Myval;
    }

    _NODISCARD const _Ty* operator->() const {
        _STL_ASSERT(_Myistr, "The stored stream pointer in_stream must be non-null");
        return _STD addressof(_Myval);
    }

    istream_iterator& operator++() {
        _Getval();
        return *this;
    }

    istream_iterator operator++(int) {
        istream_iterator _Tmp = *this;
        _Getval();
        return _Tmp;
    }

    bool _Equal(const istream_iterator& _Right) const {
        return _Myistr == _Right._Myistr;
    }

private:
    void _Getval() { // get a _Ty value if possible
        _STL_ASSERT(_Myistr, "The stored stream pointer in_stream must be non-null");
        if (!(*_Myistr >> _Myval)) {
            _Myistr = nullptr;
        }
    }

    istream_type* _Myistr{nullptr}; // pointer to input stream
    _Ty _Myval{}; // lookahead value (valid if _Myistr is not null)
};

template <class _Ty, class _Elem, class _Traits, class _Diff>
_NODISCARD bool operator==(const istream_iterator<_Ty, _Elem, _Traits, _Diff>& _Left,
    const istream_iterator<_Ty, _Elem, _Traits, _Diff>& _Right) {
    return _Left._Equal(_Right);
}

template <class _Ty, class _Elem, class _Traits, class _Diff>
_NODISCARD bool operator!=(const istream_iterator<_Ty, _Elem, _Traits, _Diff>& _Left,
    const istream_iterator<_Ty, _Elem, _Traits, _Diff>& _Right) {
    return !(_Left == _Right);
}


// CLASS TEMPLATE ostream_iterator
template <class _Ty, class _Elem = char, class _Traits = char_traits<_Elem>>
class ostream_iterator { // wrap _Ty inserts to output stream as output iterator
public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using difference_type   = void;
    using pointer           = void;
    using reference         = void;

    using char_type    = _Elem;
    using traits_type  = _Traits;
    using ostream_type = basic_ostream<_Elem, _Traits>;

    ostream_iterator(ostream_type& _Ostr, const _Elem* const _Delim = nullptr)
        : _Mydelim(_Delim), _Myostr(_STD addressof(_Ostr)) {}

    ostream_iterator& operator=(const _Ty& _Val) { // insert value into output stream, followed by delimiter
        *_Myostr << _Val;
        if (_Mydelim) {
            *_Myostr << _Mydelim;
        }

        return *this;
    }

    _NODISCARD ostream_iterator& operator*() { // pretend to return designated value
        return *this;
    }

    ostream_iterator& operator++() { // pretend to preincrement
        return *this;
    }

    ostream_iterator& operator++(int) { // pretend to postincrement
        return *this;
    }

protected:
    const _Elem* _Mydelim; // pointer to delimiter string (NB: not freed)
    ostream_type* _Myostr; // pointer to output stream
};

// CLASS TEMPLATE istreambuf_iterator
template <class _Elem, class _Traits>
class istreambuf_iterator { // wrap stream buffer as input iterator
public:
    using iterator_category = input_iterator_tag;
    using value_type        = _Elem;
    using difference_type   = typename _Traits::off_type;
    using pointer           = const _Elem*;
    using reference         = _Elem;

    using char_type      = _Elem;
    using traits_type    = _Traits;
    using streambuf_type = basic_streambuf<_Elem, _Traits>;
    using istream_type   = basic_istream<_Elem, _Traits>;

    using int_type = typename traits_type::int_type;

    constexpr istreambuf_iterator() noexcept : _Strbuf(nullptr), _Got(true), _Val() {}

    istreambuf_iterator(streambuf_type* _Sb) noexcept : _Strbuf(_Sb), _Got(!_Sb), _Val() {}

    istreambuf_iterator(istream_type& _Istr) noexcept : _Strbuf(_Istr.rdbuf()), _Got(!_Strbuf), _Val() {}

private:
    class _Istreambuf_proxy {
    public:
        _NODISCARD _Elem operator*() const {
            return _Keep;
        }

    private:
        friend istreambuf_iterator;
        _Istreambuf_proxy(streambuf_type* _Strbuf_, _Elem _Keep_) : _Strbuf(_Strbuf_), _Keep(_Keep_) {}

        streambuf_type* _Strbuf;
        _Elem _Keep;
    };

public:
    istreambuf_iterator(const _Istreambuf_proxy& _Px) noexcept : _Strbuf(_Px._Strbuf), _Got(!_Strbuf), _Val() {}

    _NODISCARD _Elem operator*() const {
        if (!_Got) {
            _Peek();
        }

#if _ITERATOR_DEBUG_LEVEL == 2
        _STL_VERIFY(_Strbuf, "istreambuf_iterator is not dereferenceable");
#endif // _ITERATOR_DEBUG_LEVEL == 2

        return _Val;
    }

    istreambuf_iterator& operator++() {
#if _ITERATOR_DEBUG_LEVEL == 2
        _STL_VERIFY(_Strbuf, "istreambuf_iterator is not incrementable");
#endif // _ITERATOR_DEBUG_LEVEL == 2

        _Inc();
        return *this;
    }

    _Istreambuf_proxy operator++(int) {
        if (!_Got) {
            _Peek();
        }

        _Istreambuf_proxy _Tmp{_Strbuf, _Val};
        ++*this;
        return _Tmp;
    }

    _NODISCARD bool equal(const istreambuf_iterator& _Right) const {
        if (!_Got) {
            _Peek();
        }

        if (!_Right._Got) {
            _Right._Peek();
        }

        return (!_Strbuf && !_Right._Strbuf) || (_Strbuf && _Right._Strbuf);
    }

private:
    void _Inc() { // skip to next input element
        if (!_Strbuf || traits_type::eq_int_type(traits_type::eof(), _Strbuf->sbumpc())) {
            _Strbuf = nullptr;
            _Got    = true;
        } else {
            _Got = false;
        }
    }

    _Elem _Peek() const { // peek at next input element
        int_type _Meta;
        if (!_Strbuf || traits_type::eq_int_type(traits_type::eof(), _Meta = _Strbuf->sgetc())) {
            _Strbuf = nullptr;
        } else {
            _Val = traits_type::to_char_type(_Meta);
        }

        _Got = true;
        return _Val;
    }

    mutable streambuf_type* _Strbuf; // the wrapped stream buffer
    mutable bool _Got; // true if _Val is valid
    mutable _Elem _Val; // next element to deliver
};

template <class _Elem, class _Traits>
_NODISCARD bool operator==(
    const istreambuf_iterator<_Elem, _Traits>& _Left, const istreambuf_iterator<_Elem, _Traits>& _Right) {
    return _Left.equal(_Right);
}

template <class _Elem, class _Traits>
_NODISCARD bool operator!=(
    const istreambuf_iterator<_Elem, _Traits>& _Left, const istreambuf_iterator<_Elem, _Traits>& _Right) {
    return !(_Left == _Right);
}

// CLASS TEMPLATE ostreambuf_iterator
template <class _Elem, class _Traits>
class ostreambuf_iterator { // wrap stream buffer as output iterator
public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using difference_type   = void;
    using pointer           = void;
    using reference         = void;

    using char_type      = _Elem;
    using traits_type    = _Traits;
    using streambuf_type = basic_streambuf<_Elem, _Traits>;
    using ostream_type   = basic_ostream<_Elem, _Traits>;

    ostreambuf_iterator(streambuf_type* _Sb) noexcept : _Failed(false), _Strbuf(_Sb) {}

    ostreambuf_iterator(ostream_type& _Ostr) noexcept : _Failed(false), _Strbuf(_Ostr.rdbuf()) {}

    ostreambuf_iterator& operator=(_Elem _Right) { // store element and increment
        if (!_Strbuf || traits_type::eq_int_type(_Traits::eof(), _Strbuf->sputc(_Right))) {
            _Failed = true;
        }

        return *this;
    }

    _NODISCARD ostreambuf_iterator& operator*() { // pretend to get designated element
        return *this;
    }

    ostreambuf_iterator& operator++() { // pretend to preincrement
        return *this;
    }

    ostreambuf_iterator& operator++(int) { // pretend to postincrement
        return *this;
    }

    _NODISCARD bool failed() const noexcept {
        return _Failed;
    }

private:
    bool _Failed; // true if any stores have failed
    streambuf_type* _Strbuf; // the wrapped stream buffer
};
_STD_END

_STDEXT_BEGIN
using _STD iterator_traits;
using _STD size_t;

// CLASS TEMPLATE checked_array_iterator
template <class _Ptr>
class checked_array_iterator { // wrap a pointer with checking
    static_assert(_STD is_pointer_v<_Ptr>, "checked_array_iterator requires pointers");

public:
    using iterator_category = typename iterator_traits<_Ptr>::iterator_category;
    using value_type        = typename iterator_traits<_Ptr>::value_type;
    using difference_type   = typename iterator_traits<_Ptr>::difference_type;
    using pointer           = typename iterator_traits<_Ptr>::pointer;
    using reference         = typename iterator_traits<_Ptr>::reference;

    constexpr checked_array_iterator() noexcept : _Myarray(nullptr), _Mysize(0), _Myindex(0) {}

    constexpr checked_array_iterator(const _Ptr _Array, const size_t _Size, const size_t _Index = 0) noexcept
        : _Myarray(_Array), _Mysize(_Size), _Myindex(_Index) {
        _STL_VERIFY(_Index <= _Size, "checked_array_iterator construction index out of range");
    }

    _NODISCARD constexpr _Ptr base() const noexcept {
        return _Myarray + _Myindex;
    }

    _NODISCARD constexpr reference operator*() const noexcept {
        return *operator->();
    }

    _NODISCARD constexpr pointer operator->() const noexcept {
        _STL_VERIFY(_Myarray, "cannot dereference value-initialized or null checked_array_iterator");
        _STL_VERIFY(_Myindex < _Mysize, "cannot dereference end checked_array_iterator");
        return _Myarray + _Myindex;
    }

    constexpr checked_array_iterator& operator++() noexcept {
        _STL_VERIFY(_Myarray, "cannot increment value-initialized or null checked_array_iterator");
        _STL_VERIFY(_Myindex < _Mysize, "cannot increment checked_array_iterator past end");
        ++_Myindex;
        return *this;
    }

    constexpr checked_array_iterator operator++(int) noexcept {
        checked_array_iterator _Tmp = *this;
        ++*this;
        return _Tmp;
    }

    constexpr checked_array_iterator& operator--() noexcept {
        _STL_VERIFY(_Myarray, "cannot decrement value-initialized or null checked_array_iterator");
        _STL_VERIFY(_Myindex != 0, "cannot decrement checked_array_iterator before begin");
        --_Myindex;
        return *this;
    }

    constexpr checked_array_iterator operator--(int) noexcept {
        checked_array_iterator _Tmp = *this;
        --*this;
        return _Tmp;
    }

    constexpr checked_array_iterator& operator+=(const difference_type _Off) noexcept {
        if (_Off != 0) {
            _STL_VERIFY(_Myarray, "cannot seek value-initialized or null checked_array_iterator");
        }

        if (_Off < 0) {
#pragma warning(suppress : 4146) // unary minus operator applied to unsigned type, result still unsigned
            _STL_VERIFY(_Myindex >= -static_cast<size_t>(_Off), "cannot seek checked_array_iterator before begin");
        }

        if (_Off > 0) {
            _STL_VERIFY(
                _Mysize - _Myindex >= static_cast<size_t>(_Off), "cannot seek checked_array_iterator after end");
        }

        _Myindex += _Off;
        return *this;
    }

    _NODISCARD constexpr checked_array_iterator operator+(const difference_type _Off) const noexcept {
        checked_array_iterator _Tmp = *this;
        _Tmp += _Off;
        return _Tmp;
    }

#ifndef __CUDACC__ // TRANSITION, VSO-568006
    _NODISCARD
#endif // TRANSITION, VSO-568006
    friend constexpr checked_array_iterator operator+(
        const difference_type _Off, const checked_array_iterator<_Ptr>& _Next) noexcept {
        return _Next + _Off;
    }

    constexpr checked_array_iterator& operator-=(const difference_type _Off) noexcept {
        if (_Off != 0) {
            _STL_VERIFY(_Myarray, "cannot seek value-initialized or null checked_array_iterator");
        }

        if (_Off > 0) {
            _STL_VERIFY(_Myindex >= static_cast<size_t>(_Off), "cannot seek checked_array_iterator before begin");
        }

        if (_Off < 0) {
#pragma warning(suppress : 4146) // unary minus operator applied to unsigned type, result still unsigned
            _STL_VERIFY(
                _Mysize - _Myindex >= -static_cast<size_t>(_Off), "cannot seek checked_array_iterator after end");
        }

        _Myindex -= _Off;
        return *this;
    }

    _NODISCARD constexpr checked_array_iterator operator-(const difference_type _Off) const noexcept {
        checked_array_iterator _Tmp = *this;
        _Tmp -= _Off;
        return _Tmp;
    }

    _NODISCARD constexpr difference_type operator-(const checked_array_iterator& _Right) const noexcept {
        _STL_VERIFY(_Myarray == _Right._Myarray && _Mysize == _Right._Mysize,
            "cannot subtract incompatible checked_array_iterators");
        return static_cast<difference_type>(_Myindex - _Right._Myindex);
    }

    _NODISCARD constexpr reference operator[](const difference_type _Off) const noexcept {
        return *(*this + _Off);
    }

    _NODISCARD constexpr bool operator==(const checked_array_iterator& _Right) const noexcept {
        _STL_VERIFY(_Myarray == _Right._Myarray && _Mysize == _Right._Mysize,
            "cannot compare incompatible checked_array_iterators for equality");
        return _Myindex == _Right._Myindex;
    }

    _NODISCARD constexpr bool operator!=(const checked_array_iterator& _Right) const noexcept {
        return !(*this == _Right);
    }

    _NODISCARD constexpr bool operator<(const checked_array_iterator& _Right) const noexcept {
        _STL_VERIFY(_Myarray == _Right._Myarray && _Mysize == _Right._Mysize,
            "cannot compare incompatible checked_array_iterators");
        return _Myindex < _Right._Myindex;
    }

    _NODISCARD constexpr bool operator>(const checked_array_iterator& _Right) const noexcept {
        return _Right < *this;
    }

    _NODISCARD constexpr bool operator<=(const checked_array_iterator& _Right) const noexcept {
        return !(_Right < *this);
    }

    _NODISCARD constexpr bool operator>=(const checked_array_iterator& _Right) const noexcept {
        return !(*this < _Right);
    }

    friend constexpr void _Verify_range(
        const checked_array_iterator& _First, const checked_array_iterator& _Last) noexcept {
        _STL_VERIFY(_First._Myarray == _Last._Myarray && _First._Mysize == _Last._Mysize,
            "mismatching checked_array_iterators");
        _STL_VERIFY(_First._Myindex <= _Last._Myindex, "transposed checked_array_iterator range");
    }

    constexpr void _Verify_offset(const difference_type _Off) const noexcept {
        if (_Off < 0) {
#pragma warning(suppress : 4146) // unary minus operator applied to unsigned type, result still unsigned
            _STL_VERIFY(
                _Myindex >= -static_cast<size_t>(_Off), "cannot seek checked_array_iterator iterator before begin");
        }

        if (_Off > 0) {
            _STL_VERIFY(_Mysize - _Myindex >= static_cast<size_t>(_Off),
                "cannot seek checked_array_iterator iterator after end");
        }
    }

    using _Prevent_inheriting_unwrap = checked_array_iterator;

    _NODISCARD constexpr _Ptr _Unwrapped() const noexcept {
        return _Myarray + _Myindex;
    }

    constexpr void _Seek_to(_Ptr _It) noexcept {
        _Myindex = static_cast<size_t>(_It - _Myarray);
    }

private:
    _Ptr _Myarray; // beginning of array
    size_t _Mysize; // size of array
    size_t _Myindex; // offset into array
};

template <class _Ptr>
_NODISCARD constexpr checked_array_iterator<_Ptr> make_checked_array_iterator(
    const _Ptr _Array, const size_t _Size, const size_t _Index = 0) {
    return checked_array_iterator<_Ptr>(_Array, _Size, _Index);
}

// CLASS TEMPLATE unchecked_array_iterator
template <class _Ptr>
class unchecked_array_iterator { // wrap a pointer without checking, to silence warnings
    static_assert(_STD is_pointer_v<_Ptr>, "unchecked_array_iterator requires pointers");

public:
    using iterator_category = typename iterator_traits<_Ptr>::iterator_category;
    using value_type        = typename iterator_traits<_Ptr>::value_type;
    using difference_type   = typename iterator_traits<_Ptr>::difference_type;
    using pointer           = typename iterator_traits<_Ptr>::pointer;
    using reference         = typename iterator_traits<_Ptr>::reference;

    constexpr unchecked_array_iterator() noexcept : _Myptr(nullptr) {}

    constexpr explicit unchecked_array_iterator(const _Ptr _Src) noexcept : _Myptr(_Src) {}

    _NODISCARD constexpr _Ptr base() const noexcept {
        return _Myptr;
    }

    _NODISCARD constexpr reference operator*() const noexcept {
        return *_Myptr;
    }

    _NODISCARD constexpr pointer operator->() const noexcept {
        return _Myptr;
    }

    constexpr unchecked_array_iterator& operator++() noexcept {
        ++_Myptr;
        return *this;
    }

    constexpr unchecked_array_iterator operator++(int) noexcept {
        unchecked_array_iterator _Tmp = *this;
        ++_Myptr;
        return _Tmp;
    }

    constexpr unchecked_array_iterator& operator--() noexcept {
        --_Myptr;
        return *this;
    }

    constexpr unchecked_array_iterator operator--(int) noexcept {
        unchecked_array_iterator _Tmp = *this;
        --_Myptr;
        return _Tmp;
    }

    constexpr unchecked_array_iterator& operator+=(const difference_type _Off) noexcept {
        _Myptr += _Off;
        return *this;
    }

    _NODISCARD constexpr unchecked_array_iterator operator+(const difference_type _Off) const noexcept {
        unchecked_array_iterator _Tmp = *this;
        _Tmp += _Off;
        return _Tmp;
    }

#ifndef __CUDACC__ // TRANSITION, VSO-568006
    _NODISCARD
#endif // TRANSITION, VSO-568006
    friend constexpr unchecked_array_iterator operator+(
        const difference_type _Off, const unchecked_array_iterator& _Next) noexcept {
        return _Next + _Off;
    }

    constexpr unchecked_array_iterator& operator-=(const difference_type _Off) noexcept {
        return *this += -_Off;
    }

    _NODISCARD constexpr unchecked_array_iterator operator-(const difference_type _Off) const noexcept {
        unchecked_array_iterator _Tmp = *this;
        _Tmp -= _Off;
        return _Tmp;
    }

    _NODISCARD constexpr difference_type operator-(const unchecked_array_iterator& _Right) const noexcept {
        return _Myptr - _Right._Myptr;
    }

    _NODISCARD constexpr reference operator[](const difference_type _Off) const noexcept {
        return *(*this + _Off);
    }

    _NODISCARD constexpr bool operator==(const unchecked_array_iterator& _Right) const noexcept {
        return _Myptr == _Right._Myptr;
    }

    _NODISCARD constexpr bool operator!=(const unchecked_array_iterator& _Right) const noexcept {
        return !(*this == _Right);
    }

    _NODISCARD constexpr bool operator<(const unchecked_array_iterator& _Right) const noexcept {
        return _Myptr < _Right._Myptr;
    }

    _NODISCARD constexpr bool operator>(const unchecked_array_iterator& _Right) const noexcept {
        return _Right < *this;
    }

    _NODISCARD constexpr bool operator<=(const unchecked_array_iterator& _Right) const noexcept {
        return !(_Right < *this);
    }

    _NODISCARD constexpr bool operator>=(const unchecked_array_iterator& _Right) const noexcept {
        return !(*this < _Right);
    }

#if _ITERATOR_DEBUG_LEVEL != 0
    friend constexpr void _Verify_range(
        const unchecked_array_iterator _First, const unchecked_array_iterator _Last) noexcept {
        _STD _Verify_range(_First._Myptr, _Last._Myptr);
    }
#endif // _ITERATOR_DEBUG_LEVEL != 0

    using _Prevent_inheriting_unwrap = unchecked_array_iterator;

    static constexpr bool _Unwrap_when_unverified = true;

    _NODISCARD constexpr _Ptr _Unwrapped() const noexcept {
        return _Myptr;
    }

    constexpr void _Seek_to(_Ptr _It) noexcept {
        _Myptr = _It;
    }

private:
    _Ptr _Myptr; // underlying pointer
};

template <class _Ptr>
_NODISCARD unchecked_array_iterator<_Ptr> make_unchecked_array_iterator(const _Ptr _It) noexcept {
    return unchecked_array_iterator<_Ptr>(_It);
}
_STDEXT_END

#pragma pop_macro("new")
_STL_RESTORE_CLANG_WARNINGS
#pragma warning(pop)
#pragma pack(pop)
#endif // _STL_COMPILER_PREPROCESSOR
#endif // _ITERATOR_