c++ - Create hana tuple with unmovable / noncopyable types -

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i'm trying wrap head around great boost::hana , try figure out how translate old school tuple code.

maybe it's bit special have types neither copyable nor moveable , want pack them in container. think policy design ...

i guess i'm not getting how create hana tuple in value world. way i'm trying doesn't work because make<tuple>(compt{}...) needs types either copyable or @ least moveable.

so not way it. or limitation of hana?

thanks!

struct nonmoveable {     nonmoveable() = default;     nonmoveable(const nonmoveable& other) = delete;      int val; };  struct simple { int val; };  template <typename ...compt> struct oldschoolcontainer {     template <int i>     auto& getcomponent()     {         return std::get<i>(components);     }      std::tuple<compt...> components; };  template <typename ...compt> struct hanacontainer {     using args_t = decltype(make<tuple>(compt{}...));      template <int i>     auto& getcomponent()     {         return components[int_<i>];     }      args_t components; };  int main() {     oldschoolcontainer<simple> simpleosc;     static_assert(std::is_same<simple&, decltype(simpleosc.getcomponent<0>())>::value, "");      hanacontainer<simple> simplehanac;     static_assert(std::is_same<simple&, decltype(simplehanac.getcomponent<0>())>::value, "");       oldschoolcontainer<nonmoveable> nonmoveableosc;     static_assert(std::is_same<nonmoveable&, decltype(nonmoveableosc.getcomponent<0>())>::value, "");      // !!! not compile because hana's tuple closure needs either move or copy     hanacontainer<nonmoveable> nonmoveablehanac;     static_assert(std::is_same<nonmoveable&, decltype(nonmoveablehanac.getcomponent<0>())>::value, "");      return 0; }

you can use hana::_tuple<...> type std::tuple. hence, following works:

#include <boost/hana/integral_constant.hpp> #include <boost/hana/tuple.hpp> #include <tuple> #include <type_traits> namespace hana = boost::hana;   struct nonmoveable {     nonmoveable() = default;     nonmoveable(const nonmoveable& other) = delete;      int val; };  struct simple { int val; };  template <typename ...compt> struct hanacontainer {     template <int i>     auto& getcomponent()     {         return components[hana::int_<i>];     }      hana::_tuple<compt...> components; };  int main() {     hanacontainer<simple> simplehanac;     static_assert(std::is_same<simple&, decltype(simplehanac.getcomponent<0>())>::value, "");      hanacontainer<nonmoveable> nonmoveablehanac;     static_assert(std::is_same<nonmoveable&, decltype(nonmoveablehanac.getcomponent<0>())>::value, "");      return 0; }

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