Well, unfortunately in C, you have to be ever so specific as to what you wanna put in the variable.

很不幸，在C语言里，给变量赋值之前,你必须搞清楚它的数据类型。

哈佛公开课 - 计算机科学课程节选

c We know it's very specific for light because in this equation is c, the speed of light. So any time you go to use this equation, if you're trying to use it for an electron, just ask yourself first, does an electron travel at the speed of light?

我们知道它只对光适用是因为在这个方程里有,光速，所以下次你们用这个方程前，如果你们要把它用到一个电子上，先问问你自己，电子的运动速度是光速吗？

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