My fear isn't about floating point equality but about equivalence. As we discussed repeatedly, nothing changed for equality, -0.0 = 0.0 just as -0 = 0 in integers. Equality works fine, though it may be surprising in some cases for floating point values because sometimes a != a and b + 1 == b.

"Exact-bitwise-equality" is yet a further different thing from equivalence. Is this what Erlang's =:= operator does? Erlang's documentation described it as "Exactly equal to" which is a very silly description (implying maybe == is approximately equal to), presumably there's formal documentation somewhere which explains what they actually meant but I didn't find it.

Presumably Exact-bitwise-equality is always defined in Erlang? In a language like Rust or C++ that's Undefined in lots of cases so this would be a terrible idea. I still think it's better not to prod this particular dragon, but you do you.