Range.hpp

template<typename value_t>
class RangeImpl
{
	class Iterator;
public:
	RangeImpl(value_t begin, value_t end, value_t step = 1) :m_begin(begin), m_end(end), m_step(step)
	{
		if (step>0 && m_begin >= m_end)
			throw std::logic_error("end must greater than begin.");
		else if (step<0 && m_begin <= m_end)
			throw std::logic_error("end must less than begin.");

		m_step_end = (m_end - m_begin) / m_step;
		if (m_begin + m_step_end*m_step != m_end)
		{
			m_step_end++;
		}
	}

	Iterator begin()
	{
		return Iterator(0, *this);
	}

	Iterator end()
	{
		return Iterator(m_step_end, *this);
	}

	value_t operator[](int s)
	{
		return m_begin + s*m_step;
	}

	int size()
	{
		return m_step_end;
	}

private:
	value_t m_begin;
	value_t m_end;
	value_t m_step;
	int m_step_end;

	class Iterator
	{
	public:
		Iterator(int start, RangeImpl& range) : m_current_step(start), m_range(range)
		{
			m_current_value = m_range.m_begin + m_current_step*m_range.m_step;
		}

		value_t operator*() { return m_current_value; }

		const Iterator* operator++()
		{
			m_current_value += m_range.m_step;
			m_current_step++;
			return this;
		}

		bool operator==(const Iterator& other)
		{
			return m_current_step == other.m_current_step;
		}

		bool operator!=(const Iterator& other)
		{
			return m_current_step != other.m_current_step;
		}

		const Iterator* operator--()
		{
			m_current_value -= m_range.m_step;
			m_current_step--;
			return this;
		}

	private:
		value_t m_current_value;
		int m_current_step;
		RangeImpl& m_range;
	};
};

template<typename T, typename V>
auto Range(T begin, T end, V stepsize)->RangeImpl<decltype(begin + end + stepsize)>
{
	return RangeImpl<decltype(begin + end + stepsize)>(begin, end, stepsize);
}

template<typename T>
RangeImpl<T> Range(T begin, T end)
{
	return RangeImpl<T>(begin, end, 1);
}

template<typename T>
RangeImpl<T> Range(T end)
{
	return RangeImpl<T>(T(), end, 1);
}