AMDG Multimethods are unsafe unless a. all combinations are valid b. all the types involved are known at the same time somewhere c. a reasonable default exist when no matching function can be found Variant handles case a. case c is true for comparisons case b can be handled something like this typedef any_tuple<_1, _1, _2, where_<random_access_iterator<_1>, callable<_2, bool(deref_result<_1>, deref_result<_1>)> > > sort_args; void sort_impl(mpl::at<sort_args, _1>::type&, mpl::at<sort_args, _1>::type&, mpl::at<sort_args, _2>::type&); template<class Iter, class F> void sort(Iter begin, Iter end, F f) { sort_args args(begin, end, f); sort_impl(get<0>(args), get<1>(args), get<2>(args)); } Would such a class be useful? Any better ideas for the interface? The big problem is the amount of metaprograming needed. 10 operations were more than msvc 7.1 could handle with my version of dynamic_any::any<> and this is much worse. In Christ, Steven Watanabe