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Iterator adaptor for random access range which has not provided iterator interfaces (C++17)
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| #pragma once | |
| #include <iterator> | |
| #include <type_traits> | |
| #include <utility> | |
| template <typename RandomAccessRange> | |
| class index_iterator { | |
| public: | |
| using target_type = RandomAccessRange; | |
| using target_pointer_type = std::add_pointer_t<RandomAccessRange>; | |
| using size_type = decltype(size(std::declval<target_type>())); | |
| using reference = decltype(std::declval<target_type>()[std::declval<size_type>()]); | |
| using value_type = std::remove_reference_t<reference>; | |
| using signed_size_type = std::make_signed_t<size_type>; | |
| using difference_type = signed_size_type; | |
| index_iterator() noexcept : target_(nullptr), index_(0) {} | |
| explicit index_iterator(target_type &target, signed_size_type index) noexcept | |
| : target_(std::addressof(target)), index_(index) {} | |
| reference operator*() const { | |
| return (*target_)[static_cast<size_type>(index())]; | |
| } | |
| index_iterator &operator++() noexcept { | |
| ++index_; | |
| return *this; | |
| } | |
| index_iterator operator++(int) noexcept { | |
| index_iterator copy = *this; | |
| ++(*this); | |
| return copy; | |
| } | |
| index_iterator &operator--() noexcept { | |
| --index_; | |
| return *this; | |
| } | |
| index_iterator operator--(int) noexcept { | |
| index_iterator copy = *this; | |
| --(*this); | |
| return copy; | |
| } | |
| signed_size_type index() const noexcept { return index_; } | |
| private: | |
| target_pointer_type target_; | |
| signed_size_type index_; | |
| }; | |
| // specialization for std::bitset | |
| template <std::size_t N> | |
| inline index_iterator<std::bitset<N>> begin(std::bitset<N> &bitset) { | |
| return index_iterator<std::bitset<N>>(bitset, 0); | |
| } | |
| template <std::size_t N> | |
| inline index_iterator<std::bitset<N>> end(std::bitset<N> &bitset) { | |
| return index_iterator<std::bitset<N>>(bitset, size(bitset)); | |
| } | |
| template <std::size_t N> | |
| inline bool operator==(const index_iterator<std::bitset<N>> &lhs, | |
| const index_iterator<std::bitset<N>> &rhs) { | |
| return lhs.index() == rhs.index(); | |
| } | |
| template <std::size_t N> | |
| inline bool operator!=(const index_iterator<std::bitset<N>> &lhs, | |
| const index_iterator<std::bitset<N>> &rhs) { | |
| return !(lhs == rhs); | |
| } | |
| namespace std { | |
| template <std::size_t N> | |
| class iterator_traits<index_iterator<std::bitset<N>>> { | |
| using iterator = index_iterator<std::bitset<N>>; | |
| public: | |
| using value_type = typename iterator::value_type; | |
| using reference = typename iterator::reference; | |
| using difference_type = typename iterator::difference_type; | |
| using iterator_category = std::bidirectional_iterator_tag; | |
| }; | |
| } // namespace std |
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