anchor.diff:      ! V_l,i+1 are computed using the information in zone i,j.
       !
   
  -    do i = U%grid%lo-2, U%grid%hi+2
  +    do i = U%grid%lo-1, U%grid%hi+1
   
          r  = Q%data(i,iqdens)
          ux = Q%data(i,iqxvel)
  
positive.code:     ! compute the flattening coefficients
      !-------------------------------------------------------------------------
  
  
  
  
      !-------------------------------------------------------------------------
      ! compute the monotonized central differences
      !-------------------------------------------------------------------------
  
      ! 4th order MC limiting.  See Colella (1985) Eq. 2.5 and 2.6 or 
      ! Saltzman 1994, page 156
      
      call build(temp, U%grid, 1)
  
negative.code:     
  
      ! clean-up
      call destroy(Q)
      call destroy(Q_l)
      call destroy(Q_r)
  
  