// vector.java 1.0

// (C) 1997 Alejandro Vázquez C.

// All rights reserved.



public class vector

{

  public double e[];



  public vector(int n)

  { e = new double[n]; }



  public vector(double x, double y)

  {

    e = new double[2];

    e[0] = x;

    e[1] = y;

  }



  public vector(double x, double y, double z)

  { 

    e = new double[3];

    e[0] = x;

    e[1] = y;

    e[2] = z;

  }



  public vector(double x, double y, double z, double t)

  { 

    e = new double[4];

    e[0] = x;

    e[1] = y;

    e[2] = z;

    e[3] = t;

  }



  public static vector rect(double x, double y)

  { return new vector(x, y); }



  public static vector rect(double x, double y, double z)

  { return new vector(x, y, z); }



  public static vector rect(double x, double y, double z, double t)

  { return new vector(x, y, z, t); }



  public static vector polar(double r, double a)

  { return new vector(r*Math.cos(a), r*Math.sin(a)); }



  public static vector polar(double r, double a1, double a2)

  { return new vector(r*Math.cos(a1)*Math.sin(a2),

                      r*Math.sin(a1)*Math.sin(a2),

                      r*Math.cos(a2)); }



  public static vector cylin(double r, double a, double z)

  { return new vector(r*Math.cos(a), r*Math.sin(a), z); }



  public static final vector i = rect(1,0,0);

  public static final vector j = rect(0,1,0);

  public static final vector k = rect(0,0,1);



  public static vector add(vector a, vector b)

    throws ArithmeticException

  {

    if (a.e.length != b.e.length)

      throw new ArithmeticException("vectors of inequal size");



    int length = a.e.length;

    vector c = new vector(length);

    for (int i=0; i<length; i++)

      c.e[i] = a.e[i] + b.e[i];

    return c;

  }



  public vector add(vector a)

  { return add(this, a); }



  public static vector sub(vector a, vector b)

    throws ArithmeticException

  {

    if (a.e.length != b.e.length)

      throw new ArithmeticException("vectors of inequal size");



    int length = a.e.length;

    vector c = new vector(length);

    for (int i=0; i<length; i++)

      c.e[i] = a.e[i] - b.e[i];

    return c;

  }



  public vector sub(vector a)

  { return sub(this, a); }



  public static vector mult(vector a, double b)

  {

    int length = a.e.length;

    vector c = new vector(length);

    for (int i=0; i<length; i++)

      c.e[i] = a.e[i] * b;

    return c;

  }



  public static vector mult(double b, vector a)

  { return mult(a,b); }



  public vector mult(double a)

  { return mult(this, a); }



  public static vector div(vector a, double b)

  {

    int length = a.e.length;

    vector c = new vector(length);

    for (int i=0; i<length; i++)

      c.e[i] = a.e[i]/b;

    return c;

  }



  public vector div(double a)

  { return div(this, a); }



  public static double dot(vector a, vector b)

    throws ArithmeticException

  {

    if (a.e.length != b.e.length)

      throw new ArithmeticException("vectors of inequal size");



    int length = a.e.length;

    double c = 0;

    for (int i=0; i<length; i++)

      c += a.e[i] * b.e[i];

    return c;

  }

    

  public double dot(vector b)

  { return dot(this, b); }



  public static vector cross(vector a, vector b)

    throws ArithmeticException

  {

    if ((a.e.length!=3) || (b.e.length!=3))

      throw new ArithmeticException("Can't cross multiply non-3d vectors");



    return new vector(a.e[1]*b.e[2] - b.e[1]*a.e[2],

                      a.e[2]*b.e[0] - b.e[2]*a.e[0],

                      a.e[0]*b.e[1] - b.e[1]*a.e[0]);

  }



  public vector cross(vector b)

  { return cross(this, b); }



  public static double abs(vector b)

  {

    double d = 0;

    for (int i=0; i<b.e.length; i++)

      d += b.e[i]*b.e[i];

    return Math.sqrt(d);

  }



  public double abs()

  { return abs(this); }



  public static vector uni(vector a)

  { return div(a, abs(a)); }

  

  public vector uni()

  { return uni(this); }



  public static vector homog(vector a, double w)

  {

    int len = a.e.length;

    vector b = new vector(len+1);

    

    for (int i=0; i<len; i++)

      b.e[i] = a.e[i]*w;



    b.e[len] = w;

    return b;

  }



  public vector homog(double w)

  { return homog(this, w); }



  public static vector norm(vector a)

  {

    int len = a.e.length - 1;

    double w = a.e[len];

    vector b = new vector(len);



    for (int i=0; i<len; i++)

      b.e[i] = a.e[i]/w;

    return b;

  }



  public vector norm()

  { return norm(this); }  

}