import java.lang.*;

/**
  * Matrix represent and provides operations on 4 by 4 matrices.
  *
  * @author Anthony Steed
  * @version 1.0
  */

public class Matrix {
  
  /*
   * Holds the actual array of values
   */
  private double m[][];
    
  /*
   * Create a new zero matrix
   */
  public Matrix() {
    m = new double[4][4];
    for (int i=0; i<4; i++)
      {
	for (int j=0; j<4; j++)
	  {
	    m[i][j] = 0.0;
	  }
      }
  }

  /*
   * Create a new matrix by copying an exisiting matrix
   * @param the matrix to copy
   */
  public Matrix(Matrix mm) {
    for (int i=0; i<4; i++) {
      for (int j=0; j<4; j++) {
	m[i][j] = mm.m[i][j];
      }
    }
  }

  /*
   * Set this matrix to the identity matrix
   */
  public void setToIdentity() {
    for(int i=0; i<4;++i) {
      for(int j=i;j<4;++j) {
	if (i==j) {
	  m[i][j] = 1.0;
	}
	else {
	  m[i][j] = m[j][i] = 0.0;
	}
      }
    }
  }
    
  /*
   * Set this matrix to product of two given matrices
   * @param m1 the matrix on the left of the product
   * @param m2 the matrix on the right of the product
   */
  public void multiplyMatrix(Matrix m1, Matrix m2) {
    for(int i=0; i<4; ++i) {
      for(int j=0; j<4; ++j) {
	m[i][j] = 0.0;
	for(int k=0;k<4;++k) {
	  m[i][j] += (m1.m[i][k]*m2.m[k][j]);
	}
      }
    }
  }

  /*
   * Set this matrix to a translation matrix where the translation is
   * given by a vector
   * @param v the translation
   */
  public void setToTranslation(Vector v) {
    setToIdentity();
    m[3][0] = v.X;
    m[3][1] = v.Y;
    m[3][2] = v.Z;
  }

  /*
   * Set this matrix to a scale matrix where the scale is
   * given by a vector
   * @param v the scale factors
   */
  public void setToScaling(Vector v) {
    setToIdentity();
    m[0][0] = v.X;
    m[1][1] = v.Y;
    m[2][2] = v.Z;
  }

  /* 
   * Set this matrix to a rotation about the X axis by the given
   * factor specified in degrees.
   * @param a the rotation angle 
   */
  public void setToXRotation(double a) {
    double cs,sn;
    cs = Math.cos(a);
    sn = Math.sin(a);

    setToIdentity();
    m[1][1] = cs;
    m[1][2] = sn;
    m[2][1] = -sn;
    m[2][2] = cs;
  }

  /* 
   * Set this matrix to a rotation about the Y axis by the given
   * factor specified in degrees.
   * @param a the rotation angle 
   */
  public void setToYRotation(double a) {
    double cs,sn;
    cs = Math.cos(a);
    sn = Math.sin(a);

    setToIdentity();
    m[0][0] = cs;
    m[0][2] = -sn;
    m[2][0] = sn;
    m[2][2] = cs;
  }

  /* 
   * Set this matrix to a rotation about the Z axis by the given
   * factor specified in degrees.
   * @param a the rotation angle 
   */
  public void setToZRotation(double a) {
    double cs,sn;
    cs = Math.cos(a);
    sn = Math.sin(a);

    setToIdentity();
    m[0][0] = cs;
    m[1][0] = -sn;
    m[0][1] = sn;
    m[1][1] = cs;
  }

  /* 
   * Set an individual element in the matrix.
   *
   * Note that rows and columns are specified from zero, not one as is
   * commonly done in texts on matrices.
   * @param x the row
   * @param y the column
   * @param v the value
   */
  public void setValue(int x, int y, double v) {
    // Note we could throw ArrayIndexOutOfBoundsException but we do
    // not because that would probably be a package error rather than
    // a user error.
    m[x][y] = v;
  }

  /* 
   * Get individual element in the matrix.
   *
   * Note that rows and columns are specified from zero, not one as is
   * commonly done in texts on matrices.
   * @param x the row
   * @param y the column
   * @return the matrix element
   */
  public double getValue(int x, int y) {
    // Note we could throw ArrayIndexOutOfBoundsException but we do
    // not because that would probably be a package error rather than
    // a user error.
    return m[x][y];
  }

}