[blinks]

Actually, they're _not_ both equal to infinity, in the mathematical sense (which I believe you're discussing) -- X / 0 is undefined.

What's equal to infinity is the limit of 1 / x as x approaches 0, and that's only from the positive side. From the negative side, it's -infinity.

[cdavid]

Nobody is discussing about usual mathematical definitions: this is about the IEEE754 standard. In that context, x / 0 is defined (to positive infinity). I was pointing the error of the OP about the explanation about Nan != Nan.