Now I'm curious what result the OP was expecting... that's how bitwise NOT should work on (IEEE 754) floating-point numbers regardless of the language, isn't it

Now I'm curious what result the OP was expecting... that's how bitwise NOT should work on (IEEE 754) floating-point numbers regardless of the language, isn't it? (4.2).toString(2); > "100.00110011001100110011001100110011001100110011001101" (~4.2).toString(2); > "-101" (~~4.2).toString(2); > "100" Perhaps the initial NOT is supposed to maintain the bits after the point? I have to go look at the spec. [Ok, looks like that not defined in the spec, and is a language-specific behavior: I have some homework now!]