4 ms·

This is also why Rust has separate PartialEq and Eq traits - the latter is only available for types that don't have weird not-self-equal values like floating po

This is also why Rust has separate PartialEq and Eq traits - the latter is only available for types that don't have weird not-self-equal values like floating point NaNs or SQL NULLs. If you lie to Rust and create a wrapper type over f32 or f64 that has Eq, then you'd get unindexable NaN keys that just sit in your hashmap forever. The real surprise to me is that Python can index NaN keys sometimes, at least by reference to the original NaN. I knew CPython does some Weird Shit with primitive values, so I assume it's because the hashmap is comparing by reference first and then by value.

tialaramex 8mo ago
> unindexable NaN keys that just sit in your hashmap forever. Although you shouldn't put nonsense in a HashMap, HashMap::drain will give you (an iterator to get) back everything you put into the HashMap even if it's nonsense and HashMap::retain will let you provide a predicate to throw away the nonsense if you want to keep everything else, while HashMap::extract_if even allows you to get the nonsense back out again to put that somewhere more sensible. These work because they don't need to find your nonsense in particular using hashing, which may now be impossible, they're just looking at everything.