I definitely support NaN not being equal to NaN in boolean logic.
If you have x = "not a number", you don't want 1 + x == 2 + x to be true. There would be a lot of potential for false equivalencies if you said NaN == NaN is true.
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It could be interesting if there was some kind of complex NaN number / NaN math. Like if x is NaN but 1x / 2x resulted in 0.5 maybe you could do some funny mixed type math. To be clear I don't think it would be good, but interesting to play with maybe.
Doesn't "1 + x == 2 + x" evaluate to true for any x with large enough magnitude? In general we should expect identities that hold true in "real" math to not hold in FP
That’s not real math though, that’s a quirk of floating point math.
But NaN is also a quirk of IEEE754 floating pount math.