“修订《环境空气质量标准》的初心就是保护人的健康。”李天威说，国内外大量环境毒理学、流行病学的研究结果都表明，PM2.5仍然是对人体健康影响最大的污染物。
But handling that stuff is slow. To calculate a string’s width it can’t call len on the string. Instead it has to pass every character through a state machine.
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