Question

I can have /[abcd]/, /(ab|cd)/, and /[^wxyz]/. Why not /(^wx|yz)/

Apparently you can achieve an exactly identical effect by simply kludging the functionality together from other features, like so: /(?!wx|yz)../.

So why not just support the feature natively? Is there an underlying reason?

Answer 1

So, imagine that (^wx|yz) means — as you apparently intend — “a two-character sequence that is neither wx nor yz“. What would (^vwx|yz) mean? Would it mean “a two- or three-character sequence that is neither vwx nor yz“? Would it mean “either a three-character sequence that is not vwx and does not start with yz, or a two-character sequence that is yz“?

The power of the character-class notation [...] — what lets it support ranges a-z, what lets it support negation, etc. — is that it always matches a single character. As soon as you remove that restriction, it’s no longer clear what these things would mean.