I've not used lua or javascript, but wouldn't it be better to choose an implmentation that silently switches between ints, floats, doubles and big-nums as needed? That way you don't limit the speed float and int operations by autoconverting up to doubles, when double precision isn't needed.
> I've not used lua or javascript, but wouldn't it be better to choose an implmentation that silently switches between ints, floats, doubles and big-nums as needed?
If you want to go through the engineering effort, sure, it might make sense to have separate int and double encodings. You have to check for the possibility of integer overflow and convert to double in that case. In particular, this is useful if you want to use Javascript's bitwise operators. See https://developer.mozilla.org/en-US/docs/SpiderMonkey/Intern... for a description of how SpiderMonkey does it. Lua just has one representation for numbers, double normally but it could be float or long depending on how you compile it. There would be no reason to have single-precision floating point or big-num representations.
Where did I say I'd use floating point numbers for integer math? Yes, let's move the conversation to a direction it never existed so that you can pretend you were right.
(The place I'd use it would be in a Javascript implementation, or a Lua implementation, and other situations where I'm designing a programming language where I want the simplicity of having only one numerical type. And that would be a 53-bit range, not 24-bit.)