Define numbers (waiting on Number / BigInt)

[annevk]

Should we define numbers and there various notation schemes? (Mathematical operators?)

It might also make sense to define null as being roughly analogous to JavaScript's null and a good initial value for variables.

[domenic]

We may want to wait to see how tc39/proposal-bigint#10 goes with regard to ES conventions, where this is more of an issue.

I agree something to make it clearer when e.g. integer division or floating-point addition is being used would be helpful. Not sure what a good solution looks like.

Null is probably harmless to add.

[domenic]

On "null": in whatwg/html#2421 I actually went with "Let serialized be an uninitialized value" because I wanted it to be very clear that every branch of the algorithm was going to end up initializing it somehow. That felt clearer than "null", especially for the other direction where null is a valid JavaScript value. Not sure if we want to take that as precedent though.

[annevk]

That kind of edge case we could also catch with an Assert perhaps (which we should also add).

[annevk]

Also, when this happens, revisit whether we need to move anything from https://html.spec.whatwg.org/#numbers.

[annevk]

tc39/ecma262#1135 is pretty close to done it seems. Once that lands we can start aligning things.

[littledan]

The BigInt PRs are all landed. In the final notation, subscripts are used on values, not operations. Values without subscripts are Numbers. I'm not sure exactly how this should apply to web specs. cc @caiolima @Ms2ger