FUN FACT about Verse now that UEFN is out: the floating point is not quite IEEE-754 double, but it's close. Specifically the functional logic programming part of Verse (which is to say, its foundation) requires a few axioms that IEEE floats don't satisfy, so the float semantics are slightly tweaked.
Specifically
1. Verse really _really_ needs ∀x: x=x to hold or all hell breaks loose, so in Verse all NaNs compare as equal to all other NaNs, and you can check for NaN-ness by testing whether they compare equal to any other known NaN.
2. Likewise, for any x, y and any pure function f, Verse needs x=y => f(x)=f(y). IEEE signed zeros break that (take e.g. f(x)=1/x).