I've recently become excited by the variant class and the apply_visitor technique. I've got a list of about 20 types that I want to handle in my variant (they're all related, so I won't need to supply 20 operator() to my visitors!). So I create a mpl::vector of the types, and then use make_variant_over to create my particular variant type. All this works fine (modulo a few days struggling to learn mpl stuff). When I compile code that declares a variable of this variant type, the compilation takes unreasonably long (like, 1.5 hours on a 2Ghz machine). For fewer types it goes much quicker, the transition to unreasonably long happens around 14 types in the mpl::vector. Side question: I finally found the macros BOOST_MPL_USE_PREPROCESSED_HEADERS and BOOST_MPL_LIMIT_VECTOR_SIZE that I had to suitably define to use such large mpl::vector-s. Are these documented anywhere, or am I missing the "suggested" way to do this? Something else I've noticed: the Intel compiler doesn't have the compilation problem! I've attached sample case code that uses 16 types, which takes less than 5 seconds to compile with Intel 8.0 and almost 200 with GCC 3.2.2 (both on linux). When I try the full 20 types I need, GCC chugs for several hours, which is unacceptable for my project. Is there anything I can do, or is this a GCC shortcoming that I need to wait for? -- - Graeme gwl@u.washington.edu "This sentence contains exactly threee erors."