anchor.diff:  
   %% @doc Preview match scan into an index for finding first "best" matches
   -spec preview(atom(),integer(),atom(),list(),term(),integer(),function(),function()) -> list().
  -preview(IndexTable,ID,Type,_SearchStrategies,{RangeStart, RangeEnd},Limit,Iff,Vnf) ->
  -    case {Vnf(RangeStart), Vnf(RangeEnd)} of
  -        {[?nav], _} -> [];
  -        {_, [?nav]} -> [];
  -        {[NormStart], [NormEnd]} ->
  -            preview_range(IndexTable, ID, Type, {NormStart, NormEnd}, Limit, Iff)
  -    end;
   preview(IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Vnf) ->
       preview(IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Vnf,<<>>).
       % [{exact_match,<<"Key0">>,<<"Value0">>,{ID,<<"Value0">>,<<"Key0">>}}
  
positive.code: preview_execute(_IndexTable, _ID, _Type, _Strategies, _Term, Limit, _Iff, _PrevStrategy, _FromStu) when Limit =< 0 -> [];
  preview_execute(IndexTable, ID, Type, [exact_match | SearchStrategies], SearchTerm, Limit, Iff, undefined, FromStu) ->
      {atomic, ResultExact} =
          imem_if:transaction(fun() -> preview_exact(IndexTable, ID, Type, SearchTerm, ?SMALLEST_TERM, Limit, Iff) end),
      ResultExact ++ preview_execute(IndexTable, ID, Type, SearchStrategies, SearchTerm, Limit - length(ResultExact), Iff, exact_match, FromStu);
  preview_execute(IndexTable, ID, Type, [head_match | SearchStrategies], SearchTerm, Limit, Iff, PrevStrategy, FromStu) ->
      StartingStu = if FromStu == <<>> -> create_starting_stu(Type, ID, head_match, SearchTerm);
  
negative.code:         _ -> Partial
      end.
  
  -spec preview_range_init(atom(), integer(), atom(), {term(), term()}, integer(), function(), tuple() | <<>>) -> list().
  preview_range_init(IndexTable, ID, Type, SearchTerm, Limit, Iff, FromStu) ->
      StartingStu = if FromStu == <<>> -> create_starting_stu(Type, ID, range_match, SearchTerm);
                       true -> FromStu
                  end,
      {atomic, ResultRange} =
          imem_if:transaction(fun() -> preview_range(IndexTable, ID, Type, SearchTerm, StartingStu, Limit, Iff) end),
      ResultRange.
  