anchor.diff:         character*30 pname 
   c
          pname = "xyz_read_coords_byname"
  +       c1 = 0.0d0
  +       c2 = 0.0d0
          write(*,*) "in "//pname
          j1 = 0
          j2 = 0
  
positive.code:        allocate(c1(n,3))
         allocate(c2(n,3))
         allocate(gr(nb))
         write(*,*) "number of atoms", n
  c       call xyz_read_coords_byname(n,c,atom1_tag,fn_in)
  30     continue
         n1=n
         n2=n
         call xyz_read_coords_byname2(n1,c1,atom1_tag,
       +                              n2,c2,atom2_tag,
       +                              fn_in)
         if(n1.eq.0.or.n2.eq.0) goto 31
         do i=1,n1
           write(34,*) (c1(i,k),k=1,3)
         end do
         do i=1,n2
           write(35,*) (c2(i,k),k=1,3)
         end do
  c
         call rdf_compute(n, n1,c1,atom1_tag,
       +                  n2,c2,atom2_tag,
       +                  nb,rmax,lat,
       +                  gr,
       +                  fn_in)
         goto 30
  31     continue
         write(*,*) "came to the end of the file"
         stop
  
         call pair_compute(rmax,lat,i1,atag,nb,infile)
  
negative.code: c       ------------------------------------
  c       read coordinates(skipping empty lines)
  c       ------------------------------------
         write(*,*) "reading coordinates"
         do i=1,n
          read(fn_in,20) bigbuf
          l=l+1
  