Class iteration_proxy_value

Source/external/json.hpp:5114–5232

	target = to_string(value);
}
template<typename IteratorType> class iteration_proxy_value
{
  public:
	using difference_type = std::ptrdiff_t;
	using value_type = iteration_proxy_value;
	using pointer = value_type *;
	using reference = value_type &;
	using iterator_category = std::input_iterator_tag;
	using string_type = typename std::remove_cv< typename std::remove_reference<decltype( std::declval<IteratorType>().key() ) >::type >::type;

  private:
	/// the iterator
	IteratorType anchor{};
	/// an index for arrays (used to create key names)
	std::size_t array_index = 0;
	/// last stringified array index
	mutable std::size_t array_index_last = 0;
	/// a string representation of the array index
	mutable string_type array_index_str = "0";
	/// an empty string (to return a reference for primitive values)
	string_type empty_str{};

  public:
	explicit iteration_proxy_value() = default;
	explicit iteration_proxy_value(IteratorType it, std::size_t array_index_ = 0)
	noexcept(std::is_nothrow_move_constructible<IteratorType>::value
			 && std::is_nothrow_default_constructible<string_type>::value)
		: anchor(std::move(it))
		, array_index(array_index_)
	{}

	iteration_proxy_value(iteration_proxy_value const&) = default;
	iteration_proxy_value& operator=(iteration_proxy_value const&) = default;
	// older GCCs are a bit fussy and require explicit noexcept specifiers on defaulted functions
	iteration_proxy_value(iteration_proxy_value&&)
	noexcept(std::is_nothrow_move_constructible<IteratorType>::value
			 && std::is_nothrow_move_constructible<string_type>::value) = default;
	iteration_proxy_value& operator=(iteration_proxy_value&&)
	noexcept(std::is_nothrow_move_assignable<IteratorType>::value
			 && std::is_nothrow_move_assignable<string_type>::value) = default;
	~iteration_proxy_value() = default;

	/// dereference operator (needed for range-based for)
	const iteration_proxy_value& operator*() const
	{
		return *this;
	}

	/// increment operator (needed for range-based for)
	iteration_proxy_value& operator++()
	{
		++anchor;
		++array_index;

		return *this;
	}

	iteration_proxy_value operator++(int)& // NOLINT(cert-dcl21-cpp)