Probably not too hard. It would come down to how easy it is to detect quoting conventions so you don't accidentally parse () chars in strings. JSON is medium-easy. I don't know where the canonical definition of s-expressions you're using comes from (is it just Common Lisp?) so I don't know how this works.

We'd like to have some more examples of formats people care about - I'm interested in generalizing this work. So if you want to followup with more detail please do.

As a clojure user, I care about EDN, but its probably too niche to spend your time on.

https://github.com/edn-format/edn

Yes!!! A generalization for other kinds of simple grammars would be awesome.

On another note. As a js programmer who deals with a ton of json, I would love v8 to adopt some of the tricks into their json parser.