anchor.diff:              fold_files_exact_element(ReadL, Directory, F, A)
       end.
   
  --spec fold_files(ProcessIndex :: non_neg_integer(),
  -                 Directory :: string() | binary(),
  +-spec fold_files(Directory :: string() | binary(),
                    F :: fold_files_f(),
                    A :: any()) ->
       any().
  
positive.code:     InitA = {ReplaceHit0, FilesSize0, Files0},
      if
          ReadL == [] ->
              fold_files(ProcessIndex, Directory, InitF, InitA);
          true ->
              fold_files_exact(ReadL, Directory, InitF, InitA)
      end.
  
negative.code:     {ReplaceHitN,
       ReplaceN,
       FilesSize3,
       Files3} = replace_fold(ReplaceHit0, Replace0, ReadL, Directory,
                              RefreshRemoveF, RefreshUpdateF, RefreshA),
      ok = replace_persist(ReplaceHitN, ReplaceN, ReplaceIndexUsed,
                           ProcessIndex, Directory),
  