code: public static void addCol(Matrix A, int j, int start, int to, double c)
      {
          for(int i = start; i < to; i++)
              A.increment(i, j, c);
      }
docs: Updates the values of column <tt>j</tt> in the given matrix to be A[:,j] = A[:,j]+ c
  
  @param A the matrix to perform he update on
  @param j the row to update
  @param start the first index of the row to update from (inclusive)
  @param to the last index of the row to update (exclusive)
  @param c the constant to add to each element