external null_pool : unit -> pool = "caml_xml_tree_nullt"
external null_tag : unit -> t = "caml_xml_tree_nullt"
external register_tag : pool -> string -> t = "caml_xml_tree_register_tag"
external null_pool : unit -> pool = "caml_xml_tree_nullt"
external null_tag : unit -> t = "caml_xml_tree_nullt"
external register_tag : pool -> string -> t = "caml_xml_tree_register_tag"
else if t == attribute then "<@>"
else if t == nullt then "<!NIL!>"
else tag_name (get_pool()) t
else if t == attribute then "<@>"
else if t == nullt then "<!NIL!>"
else tag_name (get_pool()) t