// pair class definition

template <class T, class U>
class pair
{
		T m_left;
		U m_right;
	
	public:
		pair();
		pair(const T& t, const U& u);
		const T& left() const;
		T& left();
		const U& right() const;
		U& right();
		pair& operator+=(const pair& other);
};

template <class T, class U>
pair<T, U> operator+(const pair<T, U>& a, const pair<T, U>& b);

// pair class implementation

template <class T, class U>
pair<T, U>::pair()
{
}

template <class T, class U>
pair<T, U>::pair(const T& t, const U& u) : m_left(t), m_right(u)
{
}

template <class T, class U>
const T& pair<T, U>::left() const
{
	return m_left;
}

template <class T, class U>
T& pair<T, U>::left()
{
	return m_left;
}

template <class T, class U>
const U& pair<T, U>::right() const
{
	return m_right;
}

template <class T, class U>
U& pair<T, U>::right()
{
	return m_right;
}

template <class T, class U>
pair<T, U>& pair<T, U>::operator+=(const pair& other)
{
	m_left += other.m_left;
	m_right += other.m_right;
	return *this;
}

template <class T, class U>
pair<T, U> operator+(const pair<T, U>& a, const pair<T, U>& b)
{
	pair<T, U> dup(a);
	dup += b;
	return dup;
}