anchor.diff:  dy = 0.01
   ofile = 'streamline.nc'
   
  +! ... Lineargs
  +! ...
   call lineargs_ini(na)
  -
  +if (na.eq.0) call help_write()
  +
  +call argflg('--h',hlp)
  +call argflg('-help',hlp)
  +if (hlp) then
  +  call help_write()
  +else
  +  call header()
  +endif
  +
  +call argstr('-o',out,ofile)
   call argflg('-A',agrid)
   call argflg('-C',cgrid)
   call argdbl('-dx',fdx,dx)
  
positive.code: ! ... The velocity field follows:
  ! ...      u = - dPsi/dy
  ! ...      v =   dPsi/dx
  ! *********************************************************************
  
  use cosmo
  
negative.code:   real(dp), intent(in)     :: x,y
    real(dp)                 :: psi
  
    psi = half*(x*x+y*y+x*y)
  
    end function psifunc
  
  