-->A
 A  =
    3.  - 5.    1.  
    1.    1.    1.  
  - 1.    5.  - 2.  
    3.  - 7.    8.  
-->[Q, R] = qr(A,"e")
 R  =
  - 4.472136    8.9442719  - 6.7082039  
    0.        - 4.472136     2.236068   
    0.          0.         - 4.472136   
 Q  =
  - 0.6708204  - 0.2236068    0.6708204  
  - 0.2236068  - 0.6708204  - 0.2236068  
    0.2236068  - 0.6708204  - 0.2236068  
  - 0.6708204    0.2236068  - 0.6708204  
-->Q/Q(3,1)
 ans  =
  - 3.  - 1.    3.  
  - 1.  - 3.  - 1.  
    1.  - 3.  - 1.  
  - 3.    1.  - 3.  
-->for i = 1:3, for j= i:3,
-->R(j,i) - A(:,i)'*Q(:,j)
-->end, end
 ans  =
    0.  
 ans  =
  - 1.943E-16  
 ans  =
    1.110E-16  
 ans  =
    0.  
 ans  =
  - 5.551E-16  
 ans  =
    0.