anchor.diff:  is_IPv6reference(IPv6Str) ->
       case inet_parse:ipv6_address(IPv6Str) of
   	{ok, _IPv6AsTuple} -> IPv6Str;
  -	{error, _Reason} -> throw({error, not_a_IPv6_reference})
  +	{error, _Reason} -> throw({error, not_an_IPv6_reference})
       end.
   
   
  
positive.code: parse_domain_hostport(HostPort) ->
      case sipparse_util:split_fields(HostPort, $:) of
  	{Host, Port} ->
  	    %% throw if not a numeric string
  	    list_to_integer(Port),
  	    %% throw if not a hostname
  	    is_hostname(Host),
  	    {ok, rm_trailing_dot_from_hostname(Host), Port};
  	{Host} ->
  	    %% throw if not a hostname
  	    is_hostname(Host),
  
negative.code:     %%--------------------------------------------------------------------
      %% regular test case
      io:format("test: parse_hostport/1 - 1~n"),
      {"foo.bar", 42} = sipparse_util:parse_hostport("foo.bar:42"),
      %% test trailing "." in host name
      io:format("test: parse_hostport/1 - 2~n"),
      {"foo", 42} = sipparse_util:parse_hostport("foo.:42"),
      %% trailing "." and no port
      io:format("test: parse_hostport/1 - 3~n"),
      {"foo", none} = sipparse_util:parse_hostport("foo."),
      %% IPv4 host and port
      io:format("test: parse_hostport/1 - 4~n"),
      {"1.1.1.1", 42} = sipparse_util:parse_hostport("1.1.1.1:42"),
      %% IPv4 host and no port
      io:format("test: parse_hostport/1 - 5~n"),
      {"1.1.1.1", none} = sipparse_util:parse_hostport("1.1.1.1"),
      %% IPv6 host and port
      io:format("test: parse_hostport/1 - 6~n"),
      {"[1:2:3:4:5:6:7:8]", 42} = sipparse_util:parse_hostport("[1:2:3:4:5:6:7:8]:42"),
      %% IPv6 host and no port
      io:format("test: parse_hostport/1 - 7~n"),
      {"[1:2:3:4:5:6:7:8]", none} = sipparse_util:parse_hostport("[1:2:3:4:5:6:7:8]"),
  