Negative numeric values

[benbusby]

Currently there isn't a way to define a negative value.

The easiest way to approach this would be to create new variable types that are "negative" versions of existing or future data types (int -> -int, float -> -float), but that would mean consuming slots of variable types, which is maxed out at 9 (unless we want to enforce 2-digit parsing for complex data types in the future). It would also mean some potentially weird handling of those variables. For example, we wouldn't want to write separate cases for how to handle += of a negative vs positive integer.

Another approach would be to add another public element to Y2KVar that would toggle negative/positive for that variable. I'm reluctant to do that though, since that value wouldn't really make sense for string types, so it would be a wasted cycle.

I'm open to suggestion on how to implement this.