导数等于0是否可导取决于具体情况。等于0的导数表示该函数可能存在极值点。等于0的一阶导数只是一个有极值的必要阈值，不是一个充分阈值，也就是说，有极值的地方，切线的斜率一定是0；切线斜率为0的地方，不一定是
I want to run tail on a named pipe to facilitate some binary logfile processing. The problem is that mysterious data is being added to the beginning of the stream. I run my tests by starting the erlan
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