anchor.diff:    integer, parameter :: XC_D10300 =  82
     integer, parameter :: XC_D00400 = 112
   
  -! tau mgga
  +! seven-variable derivatives up to order 4
   ! so far only linear response
  -! list under construction ...
     integer, parameter :: XC_D0000000 =  1
     integer, parameter :: XC_D1000000 =  2
     integer, parameter :: XC_D0010000 =  4
  
positive.code:   integer, parameter :: XC_D13 = 14
    integer, parameter :: XC_D04 = 15
  
  ! gga up to order 4
  ! only derivatives that are nonzero at closed-shell reference
  ! with XC_VARS_NS are here
    integer, parameter :: XC_D00000 =   1
  
negative.code: 
    subroutine xc_eval(funid, order, npoints, densities, results)
      integer, intent(in) :: funid, order, npoints
      double precision, intent(in) :: densities(:,:)
      double precision, intent(out) :: results(:,:)
      call xceval(funid,order,npoints,densities(1,1),densities(1,2),&
           results(1,1),results(1,2))
    end subroutine xc_eval
  
    subroutine xc_potential(funid, density, energy, potentials)
      integer, intent(in) :: funid    
      double precision, intent(in) :: density(:)
      double precision, intent(out) :: energy, potentials(:)
      call xcpotential(funid,density,energy,potentials)
  