Hello, I am using the enable_if construct to disable an operator() template member function of a templated variant visitor: template <typename iter_t> class iterator_compare_visitor_ : public boost::static_visitor<bool> { public: iterator_compare_visitor_(const iter_t& to_compare_to) : to_compare_to_(to_compare_to) {} template <typename variant_iter_t> typename std::enable_if< boost::mpl::contains<const_iterators_t, iter_t>::value, bool >::type operator()(const variant_iter_t& it) const { return std::is_same<variant_iter_t, iter_t>::value && it==to_compare_to_; } template <typename variant_iter_t> typename std::enable_if< boost::mpl::contains<const_reverse_iterators_t, iter_t>::value, bool >::type operator()(const variant_iter_t& it) const { return std::is_same<variant_iter_t, iter_t>::value && it==to_compare_to_.base(); } private: const iter_t& to_compare_to_; }; The compilation fails in msvc2010 with: error C2039: 'type' : is not a member of 'std::tr1::enable_if<_Test,_Type>' 1> with 1> [ 1> _Test=false, 1> _Type=bool 1> ] in this case, iter_t is not contained in const_reverse_iterators_t and so the 2nd operator() should not be enabled. Rds, MM