Method operator()

cpp/src/arrow/util/cache_test.cc:196–198

  template <typename Func,
            typename RetType = decltype(MemoizeLruThreadUnsafe(std::declval<Func>(), 0))>
  RetType operator()(Func&& func, int32_t capacity) {
    return MemoizeLruThreadUnsafe(std::forward<Func>(func), capacity);
  }
};

template <typename T>