anchor.diff:                  [R|Rs] when N==-1 ->
                       {R,{lazy_gen, fun()->
                                             get_next_unfold_app_command(
  -                                            {File1, {lazy_file_gen, NextFileGen}}, FA, MFAorPos, SearchPaths, length(Rs))
  +                                            {File1, NextFileGen}, FA, MFAorPos, SearchPaths, length(Rs))
                                     end}};
                   _ ->Nth = length(Cmds)-N+1,
                       case N==1 of 
  
positive.code:             get_next_unfold_app_command(
                {F, NextFileGen}, FA, MFAorPos, SearchPaths, -1)
      end.
  get_next_unfold_app_command({File, {lazy_file_gen, NextFileGen}}, FA, 
                              MFAorPos, SearchPaths, N) ->
      FAs= get_fun_arity({File, {lazy_file_gen, NextFileGen}}, FA, true),
      case FAs of
          []->[]; 
          [{F, A}] ->  
  
negative.code:                             {lists:nth(Nth, Cmds), 
                               {lazy_gen, fun()->
                                                  get_next_unfold_app_command(
                                                    {File1, NextFileGen}, FA, MFAorPos, SearchPaths, N-1)
                                          end}}        
                      end
              end
  