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kotlinlang

What's up with this behavior:
```fun main() {
    val x = Double.NaN
    println(x == x)
    println(listOf(x) == listOf(x))
}```

NaN != NaN under floating point comparison, as per IEEE 754.
NaN == NaN under object comparison, otherwise hashCode is broken
see <https://docs.oracle.com/javase/8/docs/api/java/lang/Double.html#equals-java.lang.Object-|https://docs.oracle.com/javase/8/docs/api/java/lang/Double.html#equals-java.lang.Object->

Wouldn't almost everyone regard hash tables with floating point keys as being a broke thing to do to start with?

in some languages yes, but the behavior is well-defined in Java (and Kotlin)

I don't think it's generally regarded as broken "in some languages", but just generally a fundamentally broken thing to do, given how weak the guarantees around floating point arithmetic actually are

at any rate seems like a poor trade-off to me but thanks for explaining the reason