namespace cranberries{

template < class F, class A, enabler_t<!enable_get_v<A>> = nullptr >
constexpr decltype(auto) operator <<= (F&& f, A&& a)
  noexcept(noexcept( f(std::forward<A>(a)) ))
{
  return f(std::forward<A>(a));
}

template < class F, class A, enabler_t<enable_get_v<A>> = nullptr >
constexpr decltype(auto) operator <<= (F&& f, A&& a)
  noexcept(noexcept( cranberries::apply(std::forward<F>(f), std::forward<A>(a)) ))
{
  return cranberries::apply(std::forward<F>(f), std::forward<A>(a));
}

}