#ifndef NODE_DWA2004110_HPP

#define NODE_DWA2004110_HPP

# include <iostream>

struct node_base

{

node_base() : m_next(0) {}

virtual ~node_base()

{

delete m_next;

}

node_base* next() const

{

return m_next;

}

virtual void print(std::ostream& s) const = 0;

virtual void double_me() = 0;

// smart code;

void append(node_base* p)

{

if (m_next)

m_next->append(p);

else

m_next = p;

}

private:

node_base* m_next;

};

inline std::ostream& operator<<(std::ostream& s, node_base const& n)

{

n.print(s);

return s;

}

template <class T>

struct node : node_base

{

node(T x)

: m_value(x)

{}

void print(std::ostream& s) const { s << this->m_value; }

void double_me() { m_value += m_value; }

private:

T m_value;

};

#endif // NODE_DWA2004110_HPP