anchor.diff:  -export([gen_iff_binterm_list_pattern/1      %% used to generate iff fun from key pattern
           ]).
   
  --export([preview/7      %% (IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff) -> [{Strategy,Key,Value,Stu}]
  -        ,preview/8      %% (IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Cont) -> [{Strategy,Key,Value,Stu}]
  +-export([preview/8      %% (IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Vnf) -> [{Strategy,Key,Value,Stu}]
  +        ,preview/9      %% (IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Vnf,Cont) -> [{Strategy,Key,Value,Stu}]
           ]).
   
   -export([binstr_accentfold/1
  
positive.code:     % ].
  
  %% @doc Preview match scan into an index for finding first "best" matches
  -spec preview(atom(),integer(),atom(),list(),term(),integer(),function(),tuple()) -> list().
  preview(_IndexTable,_ID,_Type,_SearchStrategies,_SearchTerm,_Limit,_Iff,_Cont) ->
      [].     %% ToDo: implement continuation search
      % [{exact_match,<<"Key0">>,<<"Value0">>,{ID,<<"Value0">>,<<"Key0">>}}
      % ,{head_match,<<"Key1">>,<<"Value1">>,{ID,<<"Value1">>,<<"Key1">>}}
  
negative.code: %% ===================================================================
  
  %% @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} = SearchTerm,Limit,Iff,_Vnf) when
        is_integer(RangeStart), is_integer(RangeEnd) ->
      preview_range(IndexTable, ID, Type, SearchTerm, Limit, Iff);
  preview(IndexTable,ID,Type,SearchStrategies,SearchTerm,Limit,Iff,Vnf) ->
      case Vnf(SearchTerm) of
          ['$not_a_value'] -> [];
          [NormalizedTerm | _] ->
              case is_regexp_search(SearchStrategies, NormalizedTerm) of
                  true ->
                      preview_regexp(IndexTable, ID, Type, NormalizedTerm, Limit, Iff);
                  false ->
                      FilteredStrategies = [Strategy || Strategy <- SearchStrategies, Strategy =/= re_match],
                      preview_execute(IndexTable, ID, Type, FilteredStrategies, NormalizedTerm, Limit, Iff, undefined)
              end
      end.
      % [{exact_match,<<"Key0">>,<<"Value0">>,{ID,<<"Value0">>,<<"Key0">>}}
      % ,{head_match,<<"Key1">>,<<"Value1">>,{ID,<<"Value1">>,<<"Key1">>}}
  