anchor.diff:         character*(180) buffer
          character*(180) message
          integer istatus
  -       logical overb,ohelp
  +       logical overb,ohelp,odistinct
          character*255 file_lattice,file_in,file_out
          character*16 atom1_tag
          character*16 atom2_tag
  
positive.code: 1020     FORMAT(A180)
         end
  
         subroutine mask_byname(n,c,atag,oc,mtag)
         implicit none
         integer n
  
negative.code:      +                    fn_in)
           gr = gr + gr0
           nf = nf+1
           if(nfrm.gt.0.and.nf.ge.nfrm) then
              write(*,*) "exiting because exceeded number of frames",nf,nfrm
              exit
           end if
  