NaN vs. Inf

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0 个投票

Why is

1/0 = Inf

but

[1,0]./[1,0] = [1 NaN]

shouldn't it be [1 Inf]?

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Answer 1

Image Analyst 2011-12-31

2 个投票

1/0 is infinity, but 0/0 is not infinity nor is it zero - it's just undefined (NaN).

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Matt Tearle 2011-12-31

And if you want to know *why*, think in terms of limits. lim_{x->0} 1/x = infinity. But lim_{x->0} x^2/x = 0, lim_{x->0} x/x = 1, and lim_{x_>0} x/x^2 = infinity. So there's no way to determine what a "0/0" limit might be. Hence, it's undefined (NaN).

Similarly, Inf + Inf = Inf, but Inf - Inf = NaN.

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