anchor.diff:  
   to_binterm(B) when is_binary(B) ->   imem_datatype:io_to_binterm(B);
   to_binterm(T) ->                     imem_datatype:term_to_binterm(T).
  +
  +to_datetime(B) when is_binary(B) ->  imem_datatype:io_to_datetime(B);
  +to_datetime(L) when is_list(L) ->    imem_datatype:io_to_datetime(L);
  +to_datetime(T) when is_tuple(T) ->   T.
  +
  +to_timestamp(B) when is_binary(B) -> imem_datatype:io_to_timestamp(B);
  +to_timestamp(L) when is_list(L) ->   imem_datatype:io_to_timestamp(L);
  +to_timestamp(T) when is_tuple(T) ->  T.
   
   from_binterm(B)  ->                  imem_datatype:binterm_to_term(B).
   
  
positive.code:             , add_dt, add_ts, diff_dt, diff_ts
              , to_atom, to_string, to_binstr, to_integer, to_float, to_number
              , to_tuple, to_list, to_term, to_binterm, from_binterm
              , to_decimal, from_decimal
              , byte_size, bit_size, nth, sort, usort, reverse, last
              , remap
              ]).
  
negative.code:     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
  