anchor.diff:  %% ===================================================================
   
   %% @doc Preview match scan into an index for finding first "best" matches
  --spec preview(atom(),integer(),atom(),list(),term(),integer(),function()) -> list().
  -preview(IndexTable,ID,Type,_SearchStrategies,{RangeStart, RangeEnd} = SearchTerm,Limit,Iff) when
  +-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) ->
  -    case is_regexp_search(SearchStrategies, SearchTerm) of
  -        true ->
  -            preview_regexp(IndexTable, ID, Type, SearchTerm, Limit, Iff);
  -        false ->
  -            FilteredStrategies = [Strategy || Strategy <- SearchStrategies, Strategy =/= re_match],
  -            preview_execute(IndexTable, ID, Type, FilteredStrategies, SearchTerm, Limit, Iff, undefined)
  +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">>}}
  
positive.code: -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([binstr_accentfold/1
  
negative.code:     % ].
  
  %% @doc Preview match scan into an index for finding first "best" matches
  -spec preview(atom(),integer(),atom(),list(),term(),integer(),function(),function(),tuple()) -> list().
  preview(_IndexTable,_ID,_Type,_SearchStrategies,_SearchTerm,_Limit,_Iff,_Vnf,_Cont) ->
      [].     %% ToDo: implement continuation search
      % [{exact_match,<<"Key0">>,<<"Value0">>,{ID,<<"Value0">>,<<"Key0">>}}
      % ,{head_match,<<"Key1">>,<<"Value1">>,{ID,<<"Value1">>,<<"Key1">>}}
  