Methinks I found the problem, not in numeric_cast, but in the numeric ops themselves. The divides metafunction, for example, inherits from the apply template nested inside the divides_impl template. The problem is that the primary divides_impl template inherits from if_c, which doesn't have a nested apply template, although its argument types do. The same type of problem occurs in all other numeric ops, including the comparison ops. Changing the primary *_impl template for each numeric op to something like the following code should vanquish the problem. (It did for me when I edited the appropriate files.) template <typename Tag1, typename Tag2> struct NUMERIC_OP_IMPL { template <typename N1, typename N2> struct apply { BOOST_STATIC_CONSTANT( bool, cond = BOOST_MPL_AUX_NESTED_VALUE_WKND(int, Tag1) > BOOST_MPL_AUX_NESTED_VALUE_WKND(int, Tag2) ); typedef typename eval_if_c< cond, identity<N1>, apply_wrap1< BOOST_MPL_AUX_NUMERIC_CAST< Tag1,Tag2 >, N1 > >::type n_1; typedef typename eval_if_c< cond, apply_wrap1< BOOST_MPL_AUX_NUMERIC_CAST< Tag1,Tag2 >, N2 >, identity<N2> >::type n_2; typedef typename apply_wrap2< NUMERIC_OP_IMPL< typename n_1::tag, typename n_2::tag >, n_1, n_2 >::type type; }; }; Some preprocessed files may need similar editing so that other compilers (which I don't have) will also succeed. I may be offline for a while, as I'm about to ride out yet another hurricane. HTH Cromwell Enage __________________________________ Do you Yahoo!? Yahoo! Mail is new and improved - Check it out! http://promotions.yahoo.com/new_mail