anchor.diff:         enddo
   
          Q_l%data(i+1,iqpres) = p_xp + sum_xp
  -       Q_l%data(i,iqpres) = p_xm + sum_xm
  -
  +       Q_r%data(i,iqpres) = p_xm + sum_xm
  +
  +       
       enddo
   
       ! clean-up
  
positive.code:        enddo
  
         Q_l%data(i+1,iqdens) = r_xp + sum_xp
         Q_l%data(i,iqdens) = r_xm + sum_xm
  
  
         ! velocity
  
negative.code:        enddo
  
         Q_l%data(i+1,iqxvel) = u_xp + sum_xp
         Q_r%data(i,iqxvel) = u_xm + sum_xm
  
  
         ! pressure
  