hard and fast rule

基本解释

There is no hard-and-fast rule for the ratio because it depends on the queries involved.
对于这个比率，并没有什么严格的规则，因为这依赖于所涉及的查询。
There is no hard-and-fast rule for doing this, but adopting a proper link sequence for dependent shared libraries should work most of the time.
关于这一点，没有一成不变的规则，不过，为相关的共享库采用适当的链接顺序大部分时候都会管用。
Finally, he writes his definitions, following the hard-and-fast rule that each definition must be based on what the quotations in front of him reveal about the meaning of the word.
这时他应严格遵循一条规则：每个定义都必须依据他面前的揭示该词词义的引文。
blog.sina.com.cn

This is most certainly not a hard-and-fast rule, in general I've found it to be accurate.
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