On 10/1/07, Marco Costalba <mcostalba@gmail.com> wrote:
On 10/1/07, Joel de Guzman <joel@boost-consulting.com> wrote:
Joel de Guzman wrote:
Hence, I'd like to propose an extension (or a separate library) for allowing overloads for boost.function. The example above can be declared as:
boost::overload< std::string(std::string, std:string) , std::string(std::string, char) , std::string(std::string, char const*) , std::string(char, std::string) , std::string(char const*, std::string) > concat;
Or possibly (perhaps)
typedef fusion::vector< std::string(std::string, std:string) , std::string(std::string, char) , std::string(std::string, char const*) , std::string(char, std::string) , std::string(char const*, std::string) > overloads_sequence;
boost::overload<overloads_sequence> concat;
As example changing the inheritance compositing structure from namespace detail { template <typename Sig0, typename Sig1, typename Sig2, typename Sig3> struct compose_overload_base { typedef overload<Sig0, Sig1, Sig2, Sig3> derived; typedef overload_function<final_overload_function, derived, Sig0> ov1; typedef overload_function<ov1, derived, Sig1> ov2; typedef overload_function<ov2, derived, Sig2> ov3; typedef overload_function<ov3, derived, Sig3> ov4; typedef ov4 type; }; } to namespace detail { template <typename Seq, typename derived, int n> struct do_compose { typedef typename fusion::result_of::value_at_c<Seq, n - 1>::type sig; typedef typename fusion::result_of::pop_back<Seq>::type popped_seq; typedef do_compose<popped_seq, derived, n - 1> ov; typedef overload_function<ov, derived, sig> type; }; template <typename Seq, typename derived> struct do_compose<Seq, derived, 1> { typedef typename fusion::result_of::value_at_c<Seq, 0>::type sig; typedef overload_function<final_overload_function, derived, sig> type; }; template <typename Seq> struct compose_overload_base { enum { n = fusion::result_of::size<Seq>::type::value }; typedef overload<Seq> derived; typedef typename do_compose<Seq, derived, n>::type type; }; } A little bit more complex but works for any number of arguments (sigantures). Marco