/* I am a point in three space.  I am represented in cylindrical coordinates, but I can answer my cartesian coordinates.  I am immutable. */

public class ThreeDPoint
{

	/* Create a 3D point from the given cylindrical coordinates. */

	public ThreeDPoint (double rr, double th, double xx)
	{
		r = rr;
		theta = th;
		x = xx;
	}

	/* Cylindrical accessors. */
	public double getR () {return r;}
	public double getTheta () {return theta;}
	public double getX () {return x;}

	/* Cartesian Y accessor. */

	public double getY ()
	{
		return r * Math.cos (theta);
	}

	/* Cartesian Z accessor. */

	public double getZ ()
	{
		return r * Math.sin (theta);
	}

	/* Euclidean distance metric. */

	public double distanceTo (ThreeDPoint p)
	{
		double dx = getX () - p.getX ();
		double dy = getY () - p.getY ();
		double dz = getZ () - p.getZ ();
		return Math.sqrt (dx * dx + dy * dy + dz * dz);
	}

	private double r;	/*radius.  distance from axis of cylinder.*/
	private double theta; /* angle in radians relative to some arbitrary angle */
	private double x; /* distance along the axis from some arbitrary point */
}