Class primitive_iterator_t

Source/external/json.hpp:12650–12750

@brief an iterator for primitive JSON types This class models an iterator for primitive JSON types (boolean, number, string). It's only purpose is to allow the iterator/const_iterator classes to "iterate" over primitive values. Internally, the iterator is modeled by a `difference_type` variable. Value begin_value (`0`) models the begin, end_value (`1`) models past the end. */

end_value (`1`) models past the end.
*/
class primitive_iterator_t
{
  private:
	using difference_type = std::ptrdiff_t;
	static constexpr difference_type begin_value = 0;
	static constexpr difference_type end_value = begin_value + 1;

  JSON_PRIVATE_UNLESS_TESTED:
	/// iterator as signed integer type
	difference_type m_it = (std::numeric_limits<std::ptrdiff_t>::min)();

  public:
	constexpr difference_type get_value() const noexcept
	{
		return m_it;
	}

	/// set iterator to a defined beginning
	void set_begin() noexcept
	{
		m_it = begin_value;
	}

	/// set iterator to a defined past the end
	void set_end() noexcept
	{
		m_it = end_value;
	}

	/// return whether the iterator can be dereferenced
	constexpr bool is_begin() const noexcept
	{
		return m_it == begin_value;
	}

	/// return whether the iterator is at end
	constexpr bool is_end() const noexcept
	{
		return m_it == end_value;
	}

	friend constexpr bool operator==(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
	{
		return lhs.m_it == rhs.m_it;
	}

	friend constexpr bool operator<(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
	{
		return lhs.m_it < rhs.m_it;
	}

	primitive_iterator_t operator+(difference_type n) noexcept
	{
		auto result = *this;
		result += n;
		return result;
	}