[Haskell-cafe] predicates in XML toolboxes

The XML toolboxes HaXml, HXML and the XML toolbox uses one function type (called filter) for different purposes. The functions of types predicates a -> Bool selectors, transformators a -> a list-valued functions a -> [a] are all implemented with the one type (a -> [a]). In this design predicates don't return False or True, but an empty list or a one-element list containing the input value. Transformators return single element lists. In my opinion this means a significant loss of type safety and quality of documentation. Are there more type safe XML/HTML processor libraries in Haskell?