link code

	void linkNorth(point* N) {
		north = N;
		if (N != NULL) N->setSouth(this);
	}
	void linkEast(point* E) {
		east = E;
		if (E != NULL) E->setWest(this);
	}
	void linkSouth(point* S) {
		south = S;
		if (S != NULL) S->setNorth(this);
	}
	void linkWest(point* W) {
		west = W;
		if (W != NULL) W->setEast(this);
	}