reference count的用法和樣例：
例句
- We also review reference counting and provide a primer on templates, including some of the exacting syntactic requirements.
我們同時回顧引用計數，同時提供模板入門，包括一些精確的語法要求。 - A droppable accumulator is reference counted, and is only really dropped after all the accumulators that depend on it have been dropped.
可刪除累加器是引用計數的，它只在所有依賴於它的累加器都被刪除后才真正刪除。
