template<typename T>	// Object that holds a member function pointer, has a
class state_of			// conversion ctor and has operator() defined.
{
	state_of<T> (T::* member )( int );		// Remembering this member

public:
	state_of( state_of<T> (T::* m )( int ) ) : member( m ) {}

	state_of<T> operator()( T *p, int e ) { return ( p->*member )( e ); }
};

class state_machine
{
	state_of<state_machine> current;

	state_of<state_machine> initial( int );
	state_of<state_machine> other( int );

public:
	state_machine();

	void operator()( int e ) { current = current( this, e ); }
};

state_machine::state_machine() :
current( initial )
{}

state_of<state_machine>
state_machine::initial( int event )
{
	switch( event )
	{
	case 4:		return other;
	default:	break;
	}
	return current;
}

state_of<state_machine>
state_machine::other( int event )
{
	return initial;
}


state_machine		x;

int main(int argc, char* argv[])
{
	x( 4 );		// Shift to other state
	x( 2 );		// Back to initial
	x( 7 );		// Stay there
	x( 9 );

	return 0;
}