free_boundary::free_boundary(point pstn, point nrml, unsigned int np, double S, double T, double alpha)
{
....
     this->nrml = nrml;
     this->pstn = pstn;

     this->np = np;
     this->T = T;
....
}

class free_boundary :
	public boundary
{
private:
	deque<cell> cells_ptr;
	deque<cell>::iterator cell_iter;
	unsigned int np;
	double Vn;
	double T;
	double S;
	static double erf(double x);
	point V;
public:
	void add_cell(deque<cell> *cluster_cells);
	void set_np(unsigned int np);
	int bondary_condition(deque<particle> *cluster_particle, double dt);
	free_boundary(point pstn, point nrml, unsigned int np, double S, double T, double alpha);
	free_boundary(void);
	~free_boundary(void);
};

class boundary
{
private:
	char type[6];
public:
	point nrml;
	point pstn;
	
	virtual int bondary_condition(deque<particle> *a, double dt = 0) = 0;
	void set_position(point a);	
	void set_normal(point a);
};

struct point
{
public:
	double x, y, z;
public:
	point(void);
	point(double x, double y, double z);
	~point(void);
	void print();
	double mod();
	point set(double x, double y, double z);
	friend point operator+(point a, point b);
	friend double operator*(point a, point b);
	friend point operator*(point a, double b);
	friend point operator/(point a, double b);
	friend point operator-(point a, point b);
	friend point operator!(point a);
	point vec_mult(point p1);
};