GrantMoyer

  #include <functional>
  constexpr auto flip(const auto& f) {
    return std::bind(f, std::placeholders::_2, std::placeholders::_1);
  }

  // std doesn't have a template version of placeholders::_1, _2, etc., so we need to
  // define our own. 
  template <int I> struct placeholder{};

  template<>
  template<int I>
  struct std::is_placeholder<placeholder<I>> : std::integral_constant<int, I> {};

  // flip must be an object so that the function type can be deduced without needing
  // to explicitly specify its parameters' types.
  template<typename F>
  struct flip {
    const F f;
    
    // operator() deduces the argument types when the flip object is called, but really
    // all we need to know is the number of arguments. 
    template<typename... Args>
    constexpr auto operator()(Args... args) {
      return bind_reversed(std::make_integer_sequence<int, sizeof...(Args)>{})(args...);
    }
    
    private:
    // a helper function is needed to deduce a sequence of integers so we can bind all
    // the placeholder values.
    template<int... Is>
    constexpr auto bind_reversed(std::integer_sequence<int, Is...>) {
      return std::bind(f, placeholder<sizeof...(Is) - Is>{}...);
    }
  };