The following code asserts at compile time for me. Am I doing something wrong? typedef fusion::vector2<int,int> pair; pair p(1,2); fusion::joint_view<pair, pair> x(p, p); auto begin = fusion::begin(x); auto end = fusion::end(x); int i = fusion::distance(begin, end); The assert is on line 39 of fusion/iterator/distance.hpp: template <typename Tag> struct distance_impl { // default implementation template <typename First, typename Last> struct apply : distance_detail::linear_distance<First, Last> { BOOST_MPL_ASSERT_NOT((traits::is_random_access<First>)); BOOST_MPL_ASSERT_NOT((traits::is_random_access<Last>)); }; }; In this case, First is a joint_view iterator and Last is a vector iterator, which is indeed random-access. If I simply comment out the compile-time asserts, the code compiles and works as expected. I think these asserts are bogus. OK to remove them? -- Eric Niebler BoostPro Computing http://www.boostpro.com