随机变量是一个根据概率分布取值的函数。
A random variable is a function that takes values based on a probability distribution.
因为我们不知道，势函数是否明确定义，在洞上是否取值相同。
Because what you don't know is whether your potential is actually well-defined and takes the same value when you move all around the hole.
函数查询——评分受到索引域的的数值取值或次序的函数影响。
Function Query - influence the score by a function of a field's numeric value or ordinal.
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