Hello, 1) I now managed to produce the cartesian product of 3 mpl sequences applying my custom metafunction to the resulting triplets, however it takes like 40seconds to compile. I doubt this is the optimal way to write the cartesian product metafunction. (code compiles as-is, below) 2) By the way, cartesian product hasn't been deemed generic enough to be included in the MPL? 3) what would be the equivalent of mpl::pair for 3 or more? boost::tuple or boost::variant? Your help is very appreciated, thank you, #include <iostream> #include <boost/mpl/pair.hpp> #include <boost/mpl/placeholders.hpp> #include <boost/mpl/fold.hpp> #include <boost/mpl/vector/vector0.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/joint_view.hpp> #include <boost/mpl/transform.hpp> #include <boost/mpl/for_each.hpp> #include <boost/mpl/size.hpp> #include <boost/variant.hpp> template <typename inter, typename extra, typename integ> class curve {}; template <typename inter, typename extra, typename integ> struct curve_metafunction { typedef curve<inter,extra,integ> type; }; template<typename T> struct pair_with : boost::mpl::pair<T,boost::mpl::_> {}; template<typename pair> struct triple_with : curve_metafunction < typename pair::first, typename pair::second, boost::mpl::_ > {}; template<typename Sequence1,typename Sequence2> struct sequence_product : boost::mpl::fold< Sequence1, boost::mpl::vector0<>, boost::mpl::joint_view< boost::mpl::_1, boost::mpl::transform< Sequence2, pair_with<boost::mpl::_2> > >
{}; template<typename SequencePair, typename Sequence> struct seq_seqpair_product : boost::mpl::fold< SequencePair, boost::mpl::vector0<>, boost::mpl::joint_view< boost::mpl::_1, boost::mpl::transform< Sequence, triple_with<boost::mpl::_2> > >
{}; template<typename Sequence1,typename Sequence2,typename Sequence3> struct seq_product : seq_seqpair_product< sequence_product<Sequence1,Sequence2>::type, Sequence3 > {}; typedef boost::mpl::vector<constant, linear, polynomial, cubic_spline> interpolator_types; typedef interpolator_types extrapolator_types; typedef boost::mpl::vector<simpson> integrator_types; typedef seq_product<interpolator_types, extrapolator_types,integrator_types>::type curve_types; struct type_printer { template <typename T> void operator()( T ) { std::cout<< typeid(T).name() <<std::endl; } }; int main() { std::cout<< boost::mpl::size<curve_types>::type::value <<std::endl; boost::mpl::for_each<curve_types>( type_printer() ); } -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Steven Watanabe Sent: 31 May 2008 20:51 To: boost-users@lists.boost.org Subject: Re: [Boost-users] variant<> number of template arguments AMDG Hicham Mouline wrote:
It seems make_variant_over is also limited by BOOST_VARIANT_LIMIT_TYPES. This macro is 20 on 2 platforms (linux-i386-gcc-4.1.2-boost-1.34.1 and win-i386-vs2005- boost-1.35.0)
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If I add type19, making the mpc vector have 21 types, compilation fails...
The limit of variant and the limit of mpl::vector happen to be the same. For more types, try using the numbered form of mpl vector which can handle up to 50 arguments. #include <boost/mpl/vector/vector30.hpp> typedef boost::mpl::vector21<...> types; In Christ, Steven Watanabe