text: #ifndef FWD_TYPELIST_CONCAT_H
  #define FWD_TYPELIST_CONCAT_H
  
  #include "TypeList.h"
  
  namespace aether {
  
  struct concat_t {
    template <typename... Ts, typename... Rs, typename... Os>
    constexpr auto operator()(TypeList<Ts...>, TypeList<Rs...>, Os...) const;
  
    template <typename... Ts>
    constexpr TypeList<Ts...> operator()(TypeList<Ts...>) const;
  };
  
  constexpr concat_t concat{};
  
  } // end namespace aether
  
  #endif
  