Hello, I am looking to make a class, whose definition I cannot touch, model a Range concept. To that end I use method 2, http://www.boost.org/doc/libs/1_55_0/libs/range/doc/html/range/reference/ext... However, I am unable to specialize the relevant metafunctions (range_const_iterator, range_mutable_iterator, range_iterator) since they do not have an additional template parameter that would permit me to employ enable_if. I have found this impossible without touching either the class' definition or the metafunctions. Perhaps there is some other trick I am not aware of, in which case I would greatly appreciate hearing about it. If such a trick does not exist, then should these metafunctions feature an additional template parameter? Given that this is one of the methods to extend the library, it would make sense that one wishes to do so on conditions that enable_if can check. Albert