It isn't really meaningful to call a language like this functional or imperative. It's far too simple. If you're asking about the s-expressions specifically, th

It isn't really meaningful to call a language like this functional or imperative. It's far too simple. If you're asking about the s-expressions specifically, they are very easy to parse for the same reason they are easy to read: you don't need any precedence rules. Writing interpreters in Lisp languages for Lisp languages also has a long history.