Class iterator

cpp/nd/impl/stacked_array.hpp:158–215

    }

    class iterator
    {
    public:
        iterator(const vstacked_list_array_base* a, int64_t index, int64_t parent_index)
            : a_(a)
            , parent_index_(parent_index)
            , index_(index)
        {
        }

        void operator++()
        {
            ++index_;
            if (index_ >= a_->offsets_[parent_index_] + a_->a_[parent_index_].size()) {
                ++parent_index_;
            }
        }

        void operator--()
        {
            --index_;
            if (index_ < a_->offsets_[parent_index_]) {
                --parent_index_;
            }
        }

        void operator+=(std::ptrdiff_t n)
        {
            index_ += n;
            parent_index_ = std::distance(a_->offsets_.begin(), std::ranges::upper_bound(a_->offsets_, index_)) - 1;
        }

        void operator-=(std::ptrdiff_t n)
        {
            index_ -= n;
            parent_index_ = std::distance(a_->offsets_.begin(), std::ranges::upper_bound(a_->offsets_, index_)) - 1;
        }

        std::ptrdiff_t operator-(const iterator& other) const
        {
            return index_ - other.index_;
        }

        bool operator==(const iterator& other) const
        {
            return index_ == other.index_;
        }

        array operator*() const
        {
            return a_->a_[parent_index_][index_ - a_->offsets_[parent_index_]];
        }

    private:
        const vstacked_list_array_base* a_;
        int64_t parent_index_;
        int64_t index_;
    };