Web streams are complex for users and implementers alike. The problems with the spec aren't bugs. They emerge from using the API exactly as designed. They aren't issues that can be fixed solely through incremental improvements. They're consequences of fundamental design choices. To improve things we need different foundations.
* 核心功能：每次调用next(val)，返回当前价格的跨度（往回数≤当前价格的最大连续天数）
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Note that IDW often includes a variable exponent that is applied to the distance before taking the inverse. For a given distance , the weight of the candidate becomes: