# 12.9 变量监视

有时候，当某个变量发生变化时，调用特定的函数 是一个非常有用的技巧。变量 watchpoint 便提供了这样的方法。此功能的一些可能用途包括：保持变量变化和显示的同步，以及调用调试器来跟踪某个变量的意外变化。（详情查阅 变量调试章）

下面的这些函数用来操作和查询变量的查询函数。

TODO


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