ndarray_iterator.h

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#ifndef MF_NDARRAY_ITERATOR_H_
#define MF_NDARRAY_ITERATOR_H_

#include <iterator>

namespace mf {


template<typename Array>
class ndarray_iterator :
public std::iterator<std::random_access_iterator_tag, typename Array::value_type> {
    using base = std::iterator<std::random_access_iterator_tag, typename Array::value_type>;

public:
    using typename base::value_type;
    using typename base::reference;
    using typename base::pointer;
    
    using index_type = typename Array::index_type;
    using coordinates_type = typename Array::coordinates_type;

    constexpr static std::size_t dimension = Array::dimension;

private:
    const Array array_;
    pointer pointer_ = nullptr;
    index_type index_ = 0;
    std::ptrdiff_t pointer_step_;
    std::ptrdiff_t contiguous_length_;
    
    void forward_(std::ptrdiff_t);
    void backward_(std::ptrdiff_t);

public:
    ndarray_iterator() = default;
    ndarray_iterator(const Array& array, index_type index, pointer ptr);
    ndarray_iterator(const ndarray_iterator&) = default;
    
    ndarray_iterator& operator=(const ndarray_iterator&);
    
    ndarray_iterator& operator++();
    ndarray_iterator operator++(int);
    ndarray_iterator& operator--();
    ndarray_iterator operator--(int);
    
    ndarray_iterator& operator+=(std::ptrdiff_t);
    ndarray_iterator& operator-=(std::ptrdiff_t);
    
    reference operator*() const noexcept { return *pointer_; }
    pointer operator->() const noexcept { return pointer_; }
    reference operator[](std::ptrdiff_t n) const { return *(*this + n); }
    
    friend bool operator==(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() == b.index(); }
    friend bool operator!=(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() != b.index(); }
    friend bool operator<(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() < b.index(); }
    friend bool operator<=(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() <= b.index(); }
    friend bool operator>(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() > b.index(); }
    friend bool operator>=(const ndarray_iterator& a, const ndarray_iterator& b) noexcept
        { return a.index() >= b.index(); }
    
    friend ndarray_iterator operator+(const ndarray_iterator& it, std::ptrdiff_t n)
        { auto copy = it; copy += n; return copy; }
    friend ndarray_iterator operator+(std::ptrdiff_t n, const ndarray_iterator& it)
        { auto copy = it; copy += n; return copy; }
    friend ndarray_iterator operator-(const ndarray_iterator& it, std::ptrdiff_t n)
        { auto copy = it; copy -= n; return copy; }
    friend std::ptrdiff_t operator-(const ndarray_iterator& a, const ndarray_iterator& b)
        { return a.index() - b.index(); }
    
    index_type index() const noexcept { return index_; }
    coordinates_type coordinates() const noexcept { return array_.index_to_coordinates(index_); }
};


template<typename Array>
constexpr std::size_t ndarray_iterator<Array>::dimension;


}

#include "ndarray_iterator.tcc"

#endif