anchor.diff:      io:format("test: is_language_tag  - 3~n"),
       is_language_tag("de-En-Bar"),
   
  -    %% to long sub part
  +    %% too long sub part
       io:format("test: is_language_tag  - 4~n"),
       autotest:fail(fun() -> is_language_tag("abcdabcda") end),
   
  
positive.code:     io:format("test: duration/1  - 7~n"),
      autotest:fail(fun() -> duration("P15DT5H20S") end),
  
      %% test case insensetivitiy
      io:format("test: duration/1  - 8~n"),
      #duration{weeks = 0, days = 15, hours = 5, minutes = 2, seconds = 20} = duration("p15dt5h2m20s"),
      #duration{weeks = 7, days = 0, hours = 0, minutes = 0, seconds = 0}  = duration("p7w"),
      #duration{weeks = 0, days = 15, hours = 5, minutes = 2, seconds = 20} = duration("p15Dt5H2m20S"),
      #duration{weeks = 7, days = 0, hours = 0, minutes = 0, seconds = 0} = duration("p7W"),
  
  
  
      %% iolist_to_str/1
  
negative.code: 		  [] -> D#duration{weeks = Num};
  		  _ -> throw({error, duration_has_trailing_chars_after_week_entry})
  	      end;
  	$d ->
  	    case Rest of
  		[] -> D#duration{days = Num};
  		_ -> D2 = D#duration{days = Num},
  		     duration_t(Rest, D2)
  	    end;
  	_ -> throw({error, duration_expected_PxxxDTyyy_or_PxxxW_format})
      end.
  
  