code: public double det ()
    {
      if (m_nRows != m_nCols)
        throw new IllegalArgumentException ("Matrix must be square.");
      double d = m_nPivSign;
      for (int j = 0; j < m_nCols; j++)
        d *= m_aLU[j][j];
      return d;
    }
docs: Determinant
  
  @return det(A)
  @exception IllegalArgumentException
  Matrix must be square