/**
 * Point4.java
 *
 * author: Keith McGuigan
 *
 * The Point4 class represents a world-coordinate point.
 * The class provides 4 fields, x, y, z and w.  All are public.
 * The Point4 class can represent a point or a vector.
 *
 * Edit history
 *	11/4/98 rdb	Added cross and dot methods
 *	11/3/98	rdb	Added Point4( Point4 ) constructor
 *			Added toString
 */

//package matrix;

public class Point4 extends Object {
  
  public double x;
  public double y;
  public double z;
  public double w;

  /**
   * Constructors to create the vector
   */
  public Point4() {
    this(0,0,0,1);
  }

  public Point4(double _x, double _y, double _z) {
    this(_x, _y, _z, 1);
  }

  public Point4( Point4 p ) {
    this(p.x, p.y, p.z);
    w = p.w;
  }

  public Point4(double _x, double _y, double _z, double _w) {
    super();
    x = _x;
    y = _y;
    z = _z;
    w = _w;
  }

  /**
   * Assigns a new value to this point.
   * @param	p	A vector to be copied
   */
  public void assign(Point4 p) {
    x = p.x;
    y = p.y;
    z = p.z;
    w = p.w;
  }

  /**
   * Converts instance to a string
   * @return	A string that represents the vector
   */
  public String toString() {
    return new String("<" + x + ", " + y + ", " + z + ", " + w + ">");
  }
  //------------------- cross product ----------------------------
  // return this X p
  //
  public Point4 cross( Point4 p )
  {
     return new Point4(
	   y * p.z - z * p.y,
	   z * p.x - x * p.z,
	   x * p.y - y * p.x
           );
  }
  //------------------- dot product ----------------------------
  // return this dot p (ignoring w component)
  //
  public double dot( Point4 p )
  {
     return x * p.x + y * p.y + z * p.z;
  }
}