anchor.diff:              , to_atom, to_string, to_binstr, to_integer, to_float, to_number
               , to_tuple, to_list, to_map, to_term, to_binterm, to_pid, from_binterm
               , to_decimal, from_decimal, to_timestamp, to_datetime, to_ipaddr
  -            , json_to_list, json_arr_proj, json_obj_proj, json_value
  +            , to_json, json_to_list, json_arr_proj, json_obj_proj, json_value
               , byte_size, bit_size, map_size, nth, sort, usort, reverse, last, remap, phash2
               , '[]', '{}', ':', '#keys', '#key','#values','#value', '::'
               , mfa
  
positive.code:         , to_number/1
          , to_string/1
          , to_binstr/1
          , to_atom/1
          , to_existing_atom/1
          , to_tuple/1
  
negative.code:     unary_fun({Op, A});
  expr_fun({Op, A}) when Op=='to_atom';Op=='to_tuple';Op=='to_list';Op=='to_map';Op=='to_term';Op=='to_pid';Op=='to_name';Op=='to_text';Op=='is_nav';Op=='is_val' ->
      unary_fun({Op, A});
  expr_fun({Op, A}) when Op=='to_datetime';Op=='to_timestamp';Op=='to_ipaddr';Op=='to_json' ->
      unary_fun({Op, A});
  expr_fun({Op, A}) when Op=='from_binterm';Op=='prefix_ul';Op=='phash2' ->
      unary_fun({Op, A});
  