anchor.diff:      get_one2({ok, 1, Rest}, 1, Sum, St);
   get_one1([$-|Rest], Sum, St) ->
       get_one2({ok, 1, Rest}, -1, Sum, St);
  -get_one1(Cmd, false, St) ->
  +get_one1(_Cmd, false, _St) ->
       false;
   get_one1(Cmd, Sum, St) ->
       {ok, Sum, Cmd, St}.
  
positive.code: 
  %% (1,$)w - write buffer to file
  
  write_command(Cmd, [First, Last], St) ->
      error(not_implemented).
      
  
negative.code: 
  subst_command(_, [0, _], _) ->
      error(bad_linenum);
  subst_command([$ |_Cmd0], [_First, _Last], _St0) ->
      error(bad_delimiter);
  subst_command([$\n|_Cmd0], [_First, _Last], _St0) ->
      error(bad_delimiter);
  subst_command([Sep|Cmd0], [First, Last], St0) ->
      St1 = save_for_undo(St0),
  