metaprog.h

#ifndef Rose_metaprog_h
#define Rose_metaprog_h
 
namespace Rose {
 
namespace metaprog {
 
namespace details {
 
template <typename L, typename R, bool = L::value>
struct and_t {
  static constexpr bool value = false;
};
 
template <typename L, typename R>
struct and_t<L,R,true> {
  static constexpr bool value = R::value;
};
 
template <typename L>
struct and_t<L,void,true> {
  static constexpr bool value = true;
};
 
template <typename L, typename R, bool = L::value>
struct or_t {
  static constexpr bool value = true;
};
 
template <typename L, typename R>
struct or_t<L,R,false> {
  static constexpr bool value = R::value;
};
 
template <typename L>
struct or_t<L,void,false> {
  static constexpr bool value = false;
};
 
}
 
template <typename L, typename R> struct and_t : details::and_t<L,R> {};
template <typename L, typename R> struct or_t : details::or_t<L,R> {};
 
template <typename... Elements>
struct List;
 
template <typename T>
struct is_list_t {
  static constexpr bool value = false;
};
 
template <typename... Ts>
struct is_list_t<List<Ts...>> {
  static constexpr bool value = true;
};
 
template <typename T> using enable_list = typename std::enable_if<is_list_t<T>::value>::type;
template <typename T> using disable_list = typename std::enable_if<!is_list_t<T>::value>::type;
 
template <typename... Elements>
struct list_base_t {
  template <typename L> using append_ravel  = typename L::template prepend<Elements...>;
  template <typename L> using prepend_ravel = typename L::template append<Elements...>;
 
  template <typename... Es> using append  = List<Elements..., Es...>;
  template <typename... Es> using prepend = List<Es..., Elements...>;
};
 
template <typename... Elements>
struct List : list_base_t<Elements...> {
  template <typename Functor, typename... Args>
  static inline void apply(Functor && functor, Args&&... args) {}
 
  template <template <typename> class Functor>
  using map_t = List<>;
 
  template <template <typename,typename> class Reducer>
  using reduce_t = void;
 
  template <template <typename> class Functor>
  using map_ravel_t = List<>;
 
  template <template <typename> class Predicate>
  using filter = List<>;
 
  static constexpr size_t length{0};
 
  template <size_t position>
  using at = void;
};
 
namespace details {
  template <size_t position, typename Element, typename... Elements>
  struct list_at_t {
    using type = typename List<Elements...>::template at<position-1>;
  };
 
  template <typename Element, typename... Elements>
  struct list_at_t<0, Element, Elements...> {
    using type = Element;
  };
 
  template <template <typename> class Predicate, bool, typename Element, typename... Elements>
  struct list_filter_t {
    using list = typename List<Elements...>::template filter<Predicate>;
  };
 
  template <template <typename> class Predicate, typename Element, typename... Elements>
  struct list_filter_t<Predicate, true, Element, Elements...> {
    using list = typename List<Elements...>::template filter<Predicate>::template prepend<Element>;
  };
}
 
template <typename Element, typename... Elements>
struct List<Element, Elements...> : list_base_t<Element, Elements...> {
  template <typename Functor, typename... Args>
  static inline void apply(Functor && functor, Args&&... args) {
    functor.template operator()<Element>(std::forward<Args>(args)...);
    List<Elements...>::template apply<Functor>(std::forward<Functor>(functor), std::forward<Args>(args)...);
  }
 
  template <template <typename> class Functor>
  using map_t = typename List<Elements...>::template map_t<Functor>::template prepend< typename Functor<Element>::type >;
 
  template <template <typename, typename> class Reducer>
  using reduce_t = Reducer< Element, typename List<Elements...>::template reduce_t<Reducer> >;
 
  template <template <typename> class Functor>
  using map_ravel_t = typename List<Elements...>::template map_ravel_t<Functor>::template prepend_ravel<typename Functor<Element>::list>;
 
  template <template <typename> class Predicate>
  using filter = typename details::list_filter_t<Predicate, Predicate<Element>::value, Element, Elements...>::list;
 
  static constexpr size_t length{ List<Elements...>::length + 1 };
 
  template <size_t position>
  using at = typename details::list_at_t<position, Element, Elements...>::type;
};
 
template <template<typename> class Predicate, template<typename> class Extract, template<typename> class Children>
struct tree_traversal_factory_t {
  
  template <typename RootTag>
  struct preorder_depthfirst_t {
    using head = std::conditional_t<Predicate<RootTag>::value, List<typename Extract<RootTag>::type>, List<> >;
    using tail = typename Children<RootTag>::list::template map_ravel_t<preorder_depthfirst_t>;
    using list = typename head::template append_ravel<tail>;
  };
};
 
namespace details {
 
  template<typename... Ts> struct make_void { typedef void type;};
  template<typename... Ts> using void_t = typename make_void<Ts...>::type;
 
  template <typename T, typename = void>
  struct is_iterable_t : std::false_type {};
 
  template <typename T>
  struct is_iterable_t<T, void_t<
                            decltype(std::begin(std::declval<T>())),
                            decltype(std::end(std::declval<T>())) 
                         > > : std::true_type {};
}
 
template <class C> constexpr bool is_iterable = details::is_iterable_t<C>::value;
 
}
 
namespace mp = metaprog;
 
}
 
#endif /* Rose_metaprog_h */