anchor.diff:      unary_fun({Op, A});
   expr_fun({Op, A}) when Op=='to_atom';Op=='to_tuple';Op=='to_list';Op=='to_term';Op=='to_name';Op=='to_text';Op=='is_nav' ->
       unary_fun({Op, A});
  +expr_fun({Op, A}) when Op=='to_datetime';Op=='to_timestamp' ->
  +    unary_fun({Op, A});
   expr_fun({Op, A}) ->
       ?UnimplementedException({"Unsupported expression operator", {Op, A}});
   %% Binary custom filters
  
positive.code: 
  to_binterm(B) when is_binary(B) ->   imem_datatype:io_to_binterm(B);
  to_binterm(T) ->                     imem_datatype:term_to_binterm(T).
  
  from_binterm(B)  ->                  imem_datatype:binterm_to_term(B).
  
  
negative.code:         , to_list/1
          , to_term/1
          , to_binterm/1
          , to_timestamp/1
          , to_datetime/1
          , to_name/1
          , to_text/1
          ]).
  