I'd like to use enable_if/disable_if with a meta-function that determines whether a given multi-index container has a given tagged index. But I'm not having success writing has_index<BMI,TAG>, even looking at BMI's own index<Tag> meta-function :( Does anyone know how to implement it? Below how I'd like to use it. Thanks, --DD struct ByName {}; template <class BMI> struct VCursor { virtual void filter_by_name(const string& name) { do_filter_by_name(name); } private: void do_filter_by_name( const string& name, typename boost::enable_if<has_index<BMI, ByName> >::type* /*dummy*/ = 0 ) { typedef typename BMI::template index<ByName>::type index_type; ... } void do_filter_by_name( const string& name, typename boost::disable_if<has_index<BMI, ByName> >::type* /*dummy*/ = 0 ) { throw "no name index"; } };