I'm attaching a simple patch to vector_n_chooser.hpp that replaces some template metaprogramming with preprocessor metaprogramming in the interest of improving compile times. I found this hotspot through profiling, and there are likely to be many more such patches in the near future. I could open a trac ticket and attach all the patches there, or I could just commit them to trunk as I go. Thoughts? P.S. It would be great to get some other heavy users of template metaprogramming interested in making other such changes to bring down the compile times of the core TMP libraries like MPL, Fusion, Proto, etc., etc. -- Eric Niebler BoostPro Computing http://www.boostpro.com Index: vector_n_chooser.hpp =================================================================== --- vector_n_chooser.hpp (revision 53535) +++ vector_n_chooser.hpp (working copy) @@ -25,11 +25,13 @@ #include <boost/fusion/container/vector/vector50.hpp> #endif -#include <boost/mpl/distance.hpp> -#include <boost/mpl/find.hpp> -#include <boost/mpl/begin_end.hpp> #include <boost/preprocessor/cat.hpp> +#include <boost/preprocessor/arithmetic/dec.hpp> +#include <boost/preprocessor/arithmetic/sub.hpp> +#include <boost/preprocessor/facilities/intercept.hpp> #include <boost/preprocessor/repetition/enum_params.hpp> +#include <boost/preprocessor/repetition/enum_trailing_params.hpp> +#include <boost/preprocessor/repetition/enum_params_with_a_default.hpp> namespace boost { namespace fusion { @@ -38,40 +40,23 @@ namespace boost { namespace fusion { namespace detail { - template <int N> - struct get_vector_n; + template <BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, typename T)> + struct vector_n_chooser + { + typedef BOOST_PP_CAT(vector, FUSION_MAX_VECTOR_SIZE)<BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, T)> type; + }; template <> - struct get_vector_n<0> + struct vector_n_chooser<BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, void_ BOOST_PP_INTERCEPT)> { - template <BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, typename T)> - struct call - { - typedef vector0 type; - }; + typedef vector0 type; }; #define BOOST_PP_FILENAME_1 \ <boost/fusion/container/vector/detail/vector_n_chooser.hpp> -#define BOOST_PP_ITERATION_LIMITS (1, FUSION_MAX_VECTOR_SIZE) +#define BOOST_PP_ITERATION_LIMITS (1, BOOST_PP_DEC(FUSION_MAX_VECTOR_SIZE)) #include BOOST_PP_ITERATE() - template <BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, typename T)> - struct vector_n_chooser - { - typedef - mpl::BOOST_PP_CAT(vector, FUSION_MAX_VECTOR_SIZE) - <BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, T)> - input; - - typedef typename mpl::begin<input>::type begin; - typedef typename mpl::find<input, void_>::type end; - typedef typename mpl::distance<begin, end>::type size; - - typedef typename get_vector_n<size::value>::template - call<BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, T)>::type - type; - }; }}} #endif @@ -85,14 +70,12 @@ #define N BOOST_PP_ITERATION() - template <> - struct get_vector_n<N> + template <BOOST_PP_ENUM_PARAMS(N, typename T)> + struct vector_n_chooser< + BOOST_PP_ENUM_PARAMS(N, T) + BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_SUB(FUSION_MAX_VECTOR_SIZE, N), void_ BOOST_PP_INTERCEPT)> { - template <BOOST_PP_ENUM_PARAMS(FUSION_MAX_VECTOR_SIZE, typename T)> - struct call - { - typedef BOOST_PP_CAT(vector, N)<BOOST_PP_ENUM_PARAMS(N, T)> type; - }; + typedef BOOST_PP_CAT(vector, N)<BOOST_PP_ENUM_PARAMS(N, T)> type; }; #undef N